Nutrition of draught oxen in semi-arid west Africa. 2....
Nutrition of draught oxen in semi-arid west Africa. 2. Effect of work
on intake, apparent digestibility and rate of passage of food through
the gastro-intestinal tract in draught oxen given trop residues
A. Fall’, R. A. Pearson’, P. R. Lawrence’t ad S. Fernhndez-Rivera2
Abstract
Tzu0 exprrinmfs zucre condwfcd fo irizmfigafr fhe wlnfionshi}~s befïuccu roork and iufnke 171zd digesfioll qff~oli [y
draughf oxm gizle~z millet Sfo7Jt’r. Irz fhefiusf experimwf, infnke qf nlil/et sfovu, zvaf-CY iufake, livc 7urigltf, plasnla
conccnfmfions of fviiodofhyvonine, fhyroxine mid wca-nifuogw 7uere measured irz 28 nnirnals fhaf workcd 0, 2 01
4 h/day if7 seq~zce during fhrer 3-nwk experinmtal periods. Digcsfibilify and rate $ passnge of.food rcsidzres
tl~rough fhe digcstizle tract W~YP measwed in a second rxperimcrzt on 12 aninzals 7uorki~1~ rifle 0, 2.5 or 5 Il/clny h
scquence during fhrer 2-zueek expeuimn tal periods. Ferding behaviow zvas monifored on six a~~inrals workirlg
eitkcr 0, 2.5 OY 5 h/day. Work did nef @xf infakc of millet stowr, apparent digesfibilifirs arld fhe rate of pmsqe qf
digesta fhro7@ fhc gastro-i!zfcstinal tract. This suggests thaf fhr nutrient supply fiom intake qf rorq,dqes bly
zuorkiny o.xen is mlikcl~/ to be sufficicnt to compensatefor the extra energy expended durirzg work. Food iflfake 711175
aficted by fkr quality Cl$ the millet stozw offered. Thr level of intake (If millet stozw was proportiorml to tire anlount
of leazles in fhe sfover. Foo[f irztake increased also 05 zuork progressed. Howczw, a~~inzals nzobili,-rd their body
reserves fo perfom zoork. Anirnals commed ~OYC mater m mrking days than olz dnys they WCYC af-rest in shadr.
The heaf stress fhaf zuorking animais we~e subjectcd fo did mt appenr fo iizferfere 7uith flwir di~l~sfizlr.flrnctioll.
Keywords: digestibility, draughf aninzals, food intakc, millet stozw, 7oork.
Introduction
to the depletion of circulating energy substrates.
Ideally, draught oxen must consume sufficient food
With
sustained
exercise,
muscles
draw
before and during the cropping season SO they cari
energy-yielding substrates from body reserves. Work
start work with a reasonabie live weight and perform
therefore imposes a higher energy demand, which
work. However the scarcity and poor quality of
would be expected to stimulate intake to supply
foods available before and during the early part of
energy to muscle and to replenish depleted body
the cropping season in semi-arid areas often limit
nutrients (Weston, 1985). The occurrence of fatigue is
their nutrient intake. Food intake cari be influenced
a natural result of sustained muscular activity. The
positively or negatively by work through direct or
desire to eat and ruminate may be suppressed by
indirect mechanisms. Direct effects of work on food
fatigue (Pearson and Lawrence, 1992). Physiological
intake occur through physiological changes resulting
changes in working animals also include increased
from exercise. Muscular activity induces a higher
body temperature due to heat gained from solar
metabolic rate in working animals as compared with
radiation and increased metabolism during work.
animals at-rest (Preston and Leng, 1987). This leads
The resulting heat stress could depress food intake in
working animals (Collier and Beede, 1985).
t Present address: Centre for Agriculture in the Tropics
One indirect effect of work on intake stems from the
and Subtropics.
Institute o f A n i m a l
Production,
reduced time animals have access to food. Limited
Department
of Animal Nutrition
a n d Aquaculture.
time available to eat and ruminate is a major
üniversitkit Hohenheim (MO), D-7093, Stuttgart, Germany.
constraint to increased food intake in working
217
238
Fall, Pearson, Lawrence and Fernhdez-:Rivera
ruminants (Pearson and Lawrence, 1992). Time of
feeding also affects food intake. Bakrie and Telcni
(lY91) reported reduccd f o o d i n t a k e by animals
given roughages beforc work as compared with
animals given food aftcr work.
Work also has the potential to affect digestibility of
foods by oxen directly and indirectly through
Dry matter (DM) (g/kg)
902
Y40
90s
935
changes in a range of factors including increases in
Cru& orotein CCP)
33
36
293
177
body temperature, food particle residence time in the
C;ross ;nergy (C;E<)’
gastro-intestinal
tract
a n d
effectiveness of
(MJ/kg DM)
1 ï.5
18.0
15.1
14.7
mastication on particle breakdown (Weston, 1985).
Organic math%r (OM)
Y64
Y73
898
ïF>h
Positive effects of work on food digestibility may
Neutral-detcr#ent
fibre (NDF)
789
781
293
1 9 7
s tem
f r o m t h e
cnhanccment
o f
microbial
Acid-detcrgent fibre (ADF) 539
519
131
7 2
fermentation though greater mixing of rumen
Hemicelluk~sr~ (HEM)
273
2 6 1
162
125
contents due to exercise (Matthewman and Dijkman,
1993) and higher but moderate body temperatures
resulting from work. Dctrimental effects of work on
food digestibility may result from the shift of blood
16.00 and 18.OD h. Food trnughs and buckets were
flow from the gut to muscles and peripheral tissues,
withdrawn from a11 the yens when oxen on exercise
reduction in meal frequencies (Matthewman and
schedule were working. Therefore a11 animais had
Dijkman, 19Y3), and the less thorough mastication of
equal time o f ilccess to food, but assuming work
food because of limited timc to ruminate (T’earson
restricted rumination, they did net have similar time
a n d S m i t h , 1 9 9 4 ) . T h e r e i s n e e d f o r ‘3 c l e a r
available to ruminate. Orts were regularly removed
understanding of the relation between work and
from troughs. Oxen at rest wcre tethered out of the
digestive physiology for the feeding management of
yens and in direct sunlight when other teams tvere
draught oxen
t o b e i m p r o v e d . T h i s s t u d y
working.
investigated the relationships between food intake
and the efficiencv of utilization of foods and work
EsprGrrrlfnl ilcz&. A Latin-square cross-o\\‘er des@
p e r f o r m a n c e . .
w i t h r e p e a t e d measures was a d o p t e d f o r t h i s
experiment. Treatment consisted of the number of
hours worked per day: 0, 2 and 4 h/day pulling a
Material and methods
loaded sledge along a flat circuit or performing
E.qx?rin1en
t 1
common field operations (cultivation). Oxen were
A~iininls a{?~1 fi~di~. This experiment was conducted
allotted according to their initial body weight in
from July to September 1993 at the International
three groups with average weights of 245, 273, and
Livestock Research Institute (ILRI), International
390 kg for groups 1, 2 and 3, respectively. Oxen in
Crop Research Institute for the Semi-Arid ‘Tropics
groups 1, 2 and 3 were allotted to squares 1, 2 and 3,
(ICRISAT) Sahelian Centre, Sadore, Niger. Eighteen
respectively SO that each square was formed with
local zebu oxen, aged 4 to 8 years, average live
animais of similar live weight. Rows of each square
weight 302 (s.e. 18) kg, were used. Oxen were housed
w e r e formed b y o x teams w h e r e a s c o l u m n s
in individual concrete-floored pens roofed with zinc
represented experimental periods. The experiment
sheets. Each pen was fitted with a halved empty oil
lasted 9 weeks, which was divided into three 3-week
drum as a food trough and a graduated metal bucket
periods. Treatments were applied in sequence to
for water. Individual pens were separated with
t e a m s during experimental p e r i o d s . During each
wooden planks to prevent mixing of food and food
period, three teams were idle, three teams were
spillages.
working 2 h/day and three tcams were working
4 h/day. Each team worked 3 dayslweek. Teams
Oxen were trained to pull common farm impletnents
working for 4 h/day worked 2 h in the morning and
and 55-kg metal sledges. They were given chopped
2 h in the afternoon.
millet stover nd libitw except during the working
periods. Millet stover was supplemented with a
Mcnst~uerw~~fs.
Work output, distance travelled and
concentrate mix made LIP (g/kg) of wheat bran (600),
elapsed working time were continuously measured
groundnut cake (300) and bone meal (100) at a rate of
using an ergonieter (Lawrence and Pearson, 1985).
21.3 g/kg M”.” per day (Table 1). The concentrate
W e e k l y b l o o d s a m p l e s w e r e t a k e n f o r t h e
was offered when animais rcturncd from work in the
determination of plasma urea-N (PUN), thyroxine
morning at about 11.00 h. Millet stover was given
(T,) and triiodothyronine (T,). Body weight was
when oxen finished eating the concentrate, and at
measured every week. Food offered and refusals
Nutrition of draught cattle - 2
219
were weighed every day. Refusals on the floor and
Expcrirnent 2
food left in troughs were collected separately
Anin& and feeding. This experiment was conducted
because of contamination of floor spillage by urine
from December 1994 to February 1995 at the
and water.
ICRISAT Sahelian Centre in Niger. Twelve oxen,
aged 4 to 7 years, average weight 288 (s.e. 11) kg, at
Lnbountq nnalysis. Daily fond samples were pooled
the start of the experiment, were used. They were
each week. A sample was taken and dried in a forced
housed as in experiment 1. Al1 oxen were given
air-oven to constant weight at 55°C and ground to
chopped millet stover nd libitum except during the
pass a l-mm screen. The following determinations
working hours. The stover was chopped by hand to
were made on the weekly pooled samples of foods:
lengths of about 12 to 20 cm. The millet stover was
acid-detergent fibre (ADF), neutral-detergent fibre
supplemented with a concentrate mix made up (g/
(NDF), nitrogen (N) gross energy (GE), ash and
kg) of wheat bran (400), groundnut cake (300), rock
organic matter (OM) according to the Association of
phosphate (lOO), crushed bone (100) and common
Officia1 Analytical Chemists (1990).
salt (100) (Table 1). The concentrate was given at a
daily rate of 10 g dry matter per M0.75 at 12.00 h after
Plasma T, was analysed using the fluorescence
the morning working session. Daily food allowance
polarization immunoassay technique with an Ahbot
was adjusted SO that refusals were at least equal to a
‘TDx Analyser (Abbot Laboratories, USA). The
proportion of 0.50 of food offered.
analysis for plasma T, used the IMx total T; assay
based on the microparticle enzyme immunoassay
Trcafmcnts. Treatments consisted of levels of work
technique (Abbot Laboratories, USA). !?UN was
performed: 0, 2.5 and 5 h/day achieved by walking
assayed by an enzymatic method using a Bayer
0, 6 and 12 km/day, respectively. Each team in an
Diagnostic RA-2000 random access chemistry
exercise treatment pulled a metal sledge loaded with
analyser (Bayer Diagnostics, Basingstoke, UK).
weights SO that the draught force exerted was
equivalent to proportionately 0.10 of the team live
D&l arlnl~lsis. The following statistical mode1 was
weight. Work was performed continuously, 7 days/
used to analyse food and water intake, weight
week, pulling the sledge around a flat circuit. Work
change, plasma thyroid hormones and PUN
stopped when the set distance or set time was
concentrations:
completed or when one of the oxen in the team was
unwilling to continue.
Experimental des@. A Latin-square crossover design
was used. Twelve oxen were assigned to the three
where: Y = dependent variable (food intake, water
treatment groups, two teams in each group. The
intake,
M change, plasma thyroid hormones
rows of the squares represented individual oxen,
concentration, urea-nitrogen concentration); p =
whereas columns were experimental periods. The
overall mean; S, = effect of ith square, i = 1, 2, 3;
experiment lasted 10 weeks divided into five 2-week
T(S),,,, = effect of the jth team nested within ith
periods. Observations were repeated every week in
s q u a r e , i = 1,2,3; PCS),,,, = effect o f t h e k t h
periods 1, 3 and 5. No treatment was applied during
experimental period nested within ith square, k =
periods 2 and 4 to dissipate carry-over
effects from
1,2,3; AcI, = effect of the Ith work level, 1 = 1: 0 h/
previous periods. Each square included oxen of
day, 1 = 2: 2 h/day and 1 = 3: 3 h/day; PV,,, = effect of
similar live weight. Treatments were applied in
the rnth week, m = 1,2,3; W X Plllli = interaction
seyuence during experimental periods SO that during
between the nzth week and the kth period; W X A,,,, =
each period four oxen were idle, four oxen were
interaction between the mth week and the lth work
working 2.5 h/day and four oxen were working 5 h/
level; W X T(Sjci,,,,, = interaction between the mth
day.
week and the jth team in the ith square; Eiikl,ri = effect
peculiar to the jth team in the ith square subjected to
Mensuwmenfs.
Sampling,
measurements
a n d
the Ith level of work in nzth week of the kth period.
laboratory analyses were as in experiment 1 with the
following amendments and additions.
The term T(S),,,, was used as the error term to test the
effect of work. The sums of squares for treatment
Work: an ergometer was used only during the
and week were further partitioned into single
preparation phase of this experiment, to measure
degrees of freedom using polynomial contrasts (i.e.
work performed, distance travelled and elapsed
A,). Weekly live-weight changes were estimated by
working time for different known work loads. A
regression analysis and were further subjected to
regression analysis of force on work load was
analysis of variante using generalized linear models
derived and used to determine the load required for
(Statistical Analysis Systems Institute (SAS), 1985).
each team SO that the draught force exerted was
220
Fall, Pearson, Lawrence and Fernandez-Rivera
equivalent to proportionatelv 0.10 of the team live
water intake, M change, plasma thyroid hormones
weight The time taken to travel around the circuit
and PUN concentrations included as main factors:
was measured with a stop watch.
square, ox nested within square, experimental period
nested within square, treatment (number of hours
lntnke nnd appamt digestibility qf food: each day a
worked), week and the interactions between these
sample of millet stover was taken before chopping
terms. Sources of variation for the analysis of
the stover. At the end of each week the daily millet
apparent digestibility coefficients were: square, ox
stover samples were pooled and plant parts were
nested within square, period nested within square
separated and weighed to determine proportion of
and treatment.
leaves in the stover.
Orthogonal linear and quadratic polynomials were
Three digestibility trials were conducted, one in each
used to test the effect of treatment. A regression
2-week period. Total faecal collection was carried out
analysis of dry matter intake (DMJ) and dry-matter
for 7-day periods using faecal bags harnessed to oxen
apparent digestibility (DMD) on the proportion of
throughout the collection period. The faecal bags
leaf in the stover was performed. Sources of variation
were emptied regularly and the faeces weighed and
for the analysis of time spent eating and ruminating,
placed into a bucket, stored in a cool place. At the
were treatment, oxen within treatment and time of
end of each day, faeces were mixed and a sample
observation.
(proportionately 0.05) was taken and frozen. At the
end of each 7-day collection period, daily samples
were thawed, mixed and a subsample (1 kg) was
taken and oven dried at 55°C.
Results
Expcrinrent 2
Rate
of passage
of food:
sixty grams of
Minimum,
maximum
a n d
mean
ambient
chromium-mordanted fibre were given on dny 7 of
temperatures were 23.0, 35.0 and 29.3”C when
the first and the second periods (Mathers et a/., 1989).
animals worked in the morning and 23.0, 36.0 and
On that day food was withdrawn from 14.00 until
31.7”C when work took place in the afternoon.
23.00 h when the markers were given. Faecal samples
Minimum, maximum and mean relative humidities
were collected at regular intervals as follows: 9,11,13,
were 0,400, 0.930 and 0.674 during the morning
15,17,19,21,24,33,37,39,41,43,47,57,61,65,
71,81,
working sessions and 0.440, 0.960 and 0.600 during
85,89,95,105,109,113,119,129,137,153,l61,177
and
the afternoon working sessions.
185 h after dosing. lndividual faecal samples were
thoroughly mixed and a sample was taken for the
Plasma T, and T, concentrations were not affected by
determination of dry matter and Cr concentration.
level of work (Table 2). There was a significant linear
Gastro-intestinal mean retention time was estimated
increase in PUN as level of work increased (P < 0.01;
using Grovum and Williams (1973) mathematical
Table 2).
procedures,
after a single dose of marker.
Daily DM1 of millet stover was not affected by
Feeding beknaiour: s i x o x e n , t w o o x e n i n each
number of hours worked per day. There was a
treatment group, were selected for the observation of
significant linear increase over the weeks in daily
feeding behaviour during the first period of the
DM1 expressed in kg DM (P < O.Ol), in g DM per kg
experiment. The behaviour of each animal was
M”.7i (P < 0.01) and in g DM per kg M (P < 0.05). The
monitored during a 3-h observation period every 5
interaction between treatment and week was
min. Two or three 3-h observation sessions were
significant for DMI-g/kg M and close to significance
carried out each day. At the end of the 4th day, the
at the 5% probability level (P = 0.07) for DMI-g/kg
combination of the 3-h observation periods yielded a
M”‘?“. Table 2 shows daily work characteristics, food
24-h composite behaviour pattern of the animais.
and water intake and weekly live-weight changes.
This scheme was applied three times consecutively.
Food intakes of animais working 2 and 4 h/day
During each 5-min observation period each of the six
include food consumption
on non-working and
animais was observed. The time spent doing a
working days. High intensities of work (4 h/day)
particular activity (eating, ruminating, standing,
depressed intake in working oxen during the first
lying) was estimated as the product of the number of
days of work. However, these animais were able to
tomes this activity was observed and the interval
increase their intake the following days such that
between observations (5 min).
they could eat as much as oxen at rest or oxen
working lightly.
Sfatistical aualysis. Data werc analysed using SAS
GLM procedures (SAS, 1985). The statistical mode1
There were no significant differences
due to work in
used to analyse daily intake of millet stover, daily
water consumption
expressed in I/day, l/kg M, l/kg
Work level
Variables
0 h/day
2 h/day
4 h/day
Significance
Work characteristics
Daily work output (kJ)
3233
(0.22)t
6763
(0.33)
Load (N/kg M)
0.89 (0.26)
0.88 (0.23)
Power (W)
583
(0.11)
616
(0.10)
Power (W/lOO kg)
Y0 (0.28)
92 (0.18)
Mean
s.e.
Mean
5.e.
Mean
s.e.
Daily intake of millet stover
k g D M
4.72
cl.045
4.78
0.049
4.60
0.049
g DM/kg M
15.46
0.17
15.94
0.19
15.50
0.19
g DM/ kg M’),7i
64.40
0.65
66.06
0.72
64.04
0.72
Daily water intake
litre (1)
30.5
0.47
30.2
0.51
30.3
0.51
b’kg M
0.099
0.001
0.099
0.002
0.101
0.002
1 /kg Ml’.”
0.41
0,007
0.42
Od~O8
0.42
0.008
l/kg DM1
6.45
0.09
6.32
0.09
6.58
0.09
T, (nmol/l)
56.3
1.2
52.7
1.2
52.3
1.2
T, (nmol/l)
0.95
0.03
0.94
0.03
0.98
0.03
PUN (mmol/l)
4.0
1.14
4.5
0.14
4.83
0.14
LineaP
Live-weight change (kg/week)
3.72
0.76
1.58
0.84
-2.19
0.82
*
t Values in parentheses are CVs.
M0-7i or l/kg DM1 (Table 2). In this experiment, oxen
DM1 (g/kg M@75) = 52.5 (se. 4.44) + 20.8 (se. 7.65) X PLS
at-rest were tethered in the suri while other teams
(P < 0.01; R’ = 0.28).
were working. Body-weight change was significantly
affected by work (P < 0.05; Table 2).
Table 3 Experimmt 2: lenst-squnré mms for infake of millet
stowr, watrr intake, liue zueight sud plasma concm tration of urea
Expriment 2
rzifrogm (PLIN) ofoxen zuorking 0,2,5 atzd 5 h/day
There was a significant linear increase in PUN
concentration as work level increased (P < 0.05; Table
Work level
3). The effects of week and the interaction between
0 h/day
25 h/day 5 h/day
St.
work level and week were also significant
(P < 0.001). Increases of PUN over weeks were
Intake of
greatest as work level increased.
millet stover
dkg M
1 5 . 1 3
16.22
16.15
0.20
Plasma TJ concentration decreased as work Ievel
g/kg M”,i5
61.36
65.82
65.51
0.83
increased (Table 4). There was a significant linear
Water intake
decrease (P < 0.01) in plasma T, concentrations as
I/day
21.35"
25.20h
28.51c
0,380
work load increased and over weeks (P < 0.001).
l/kg M
0.08"
0.09"
0.11'
0.014
I/kg M”,7”
0.32"
0.3Bh
0.43c
0.050
l/kg DM1
5.37"
5,83b
6.44'
0.120
Intake of millet stover was not significantly
PUN (mmol/l)t
influenced by work. Table 3 shows mean DMI, water
Before work
4.37
3.68
3.90
0.31
intake and live weight over 2-week experimental
W e e k 1
3.02
3.42
4.30
0.31
periods for oxen working 0, 2.5 and 5 h/day. The
Week 2
3.17
4.53
5.78
0.31
relationship between intake and the proportion of
Live weight (kg)t
leaf in the stover (PLS) is described by the following
Week 1
597
610
615
3
regression equations that show an improvement in
W e e k 2
599
602
597
3
food intake as the proportion of leaves increased:
t See text for the significance of factors (work and week)
included in the analysis of variante.
DM1 (g/kg M) = 12.8 (s.e. 1.09) + 5.4 (se. 1.18) X PLS
a,h.c Values in the same row with different superscripts are
(P < 0.01; R2 = 0.30)
significantly different P < 0.05.
--
--
.- _-~
222
Fall, Pearson, Lawrence and Fernhdez-Rivera
Apparent digestibilityt
DM
0.42
043
OI3
0.011
OM
0.45
046
0.45
0,012
ADF
0.54
0.54
0.55
0.010
NDF
0.57
0.57
0.58
0.009
HEM
0.63
0.63
0.65
0.009
G E
049
04
0.51
0~009
T4 (nmol/l)S
Before work
48.6
45.3
48.0
2.6
Week 1
49.0
444
38.7
2.6
Week 2
45.5
34.6
27.7
2.6
T, (nmol/l)$
Before work
0.77
0.69
0.64
0.04
Weck 1
0.69
OdA
062
04~4
Week 2
0450
04
0.39
ool
Time spent eating (min/day)
375
385
455
45
Time spent ruminating (min/day)
339
400
344
4 2
Time spent eating and ruminating (min/day)
715
785
799
49
Eating rate (g DM1 per min)
14.l
10.9
15.3
2.h
Rumination rate (min/g DMI)
88.3
108.1
78.7
10.5
MRT (h)
88.9
78.2
82.2
2.3
Quadratic ’
TT 04
14.17
14.54
13.28
14
llk,
56.9
49.1
52.3
2.8
llk,
17.9
14.6
16.6
1.2
t For abbreviations see Table 1.
$ See text for the significance of factors (work and weeks) included in the analysis of variante.
There was a significant increase in water intake as
HEMD = 0.14 (se. 0.05) + 0.87 (se. 0.09) X PLS
work level increased (Table 3). Work caused
(P < 0.01, R’ = 0.72)
live-weight losses whereas oxen at-rest were able to
maintain their body weight (Table 3).
GED = 0.12 (se. 0.04) + 0.67 (s.e. 0.08) X PLS
(P < 0.01, X2 = 0.66).
There was no significant effect of work on the
apparent digestibility of DM, OM, ADF, NDF,
The estimated values for the two rate constants (k,,
hemicellulose (HEM) and GE. Table 4 shows
k2), the calculated time of first appearance of marker
coefficients of apparent digestibility for diiferent
in faeces (TT) and the mean retention time (MRT) are
work loads. Increases in the proportion of leaves in
shown in Table 4 for Cr-fibre. The rate constants k,
the food offered improved apparent digestibility
and k2 refer to the proportion of matter leaving the
coeffficients
as illustrated by the regression o f
rumen and the large intestine, respectively. Their
apparent digestibility coefficients on PLS given in the
reciprocals represent the retention time in each pool
following equations:
(Grovum and Williams, 1973). Work did not
significantly influence TT, k, and kT However, the
DMD = 0.03 (se. 0.08) + 0.69 (s.e. 0.08) X PIS
quadratic effect of work on MRT was significant
(P < 0.01, R2 = 0.68)
(P < 0.05). Work did not significantly affect time
spent eating and
ruminating or eating and
ADFD = 0.25 (se. 0.04) + 0.52 (se. 0.08) X PIS
rumination rates (Table 4).
(P < 0.01, R2 = 0.52)
NDFD = 0.19 (se. 0.04) + 0.68 (se. 0.08) X PIS
Discussion
(P < 0.01, R2 = 0.69 )
In experiment 1 there was an absence of significant
differenccs in plasma T, and T, concentrations
OMD = 0.06 (se. 0.05) + 0.70 (se. 0.09) X PIS
between working oxen and oxen at-rest. However in
(P < 0.01, R2 = 0.65)
experiment 2, the higher the work load, the greater
Nutrition of draught cattle - 2
223
was the decrease in plasma T, and T,. Decreases in
Most results show little difference
in intake in
plasma T7 and T, concentrations as a response to heat
working animals compared with animals at-rest
stress were reported by Pearson and Archibald
(reviewed by Pearson and Dijkman, 1994). The
(1990) and El-Nouty and Hassan (1983). During
absence of an effect of work on food intake when
experiment 2, unlike experiment 1, oxen at-rest were
time of access to food was standardized, as in this
not exposed to solar radiation and ambient
study, was reported by Pearson and Lawrence (1992)
temperatures were lower. Differences
in heat stress
and Pearson and Smith (1994) in cattle and by
between working and non-working oxen were great
Bamualim and Ffoulkes (1988) and Bakrie cf nl. (1988)
enough to induce significant differences in plasma
in buffaloes.
concentrations of T, and T, between the groups.
The effect of work on food intake may result from
The higher heat load of working oxen during
the work stress and/or from the food restriction
experiment 2 relative to oxen at rest did not translate
during hours animals work (Pearson and Smith,
into significant changes in food intake and
1994). In the present study oxen at-rest and working
digestibility. Christopherson and Kennedy (1983)
oxen had equal time available to eat. It was assumed
suggest that extremes of heat or cold are needed
that oxen at-rest had more opportunities to ruminate
before marked differences in digestibility are seen. It
than working oxen because oxen rarely ruminate
is also probable that animals used in these
when they work. Since food intake was not
experiments, being born in the area, were well
significantly different between working and
adapted to high ambient temperatures.
non-working oxen during both experiments, then the
limited time available to ruminate may not have
Although little quantitative information is available,
been a significant inhibitor of food intake in working
it is generally assumed that oxen need to consume
oxen in these experiments. Results in experiment 2
more water during working days as compared with
showed the time spent eating and ruminating was
non-working days, particularly under hot conditions
similar whether animals worked 0, 2.5 or 5 h/day.
to compensate for water lost through evaporative
Clearly, a 5-h period of food deprivation, with or
cooling processes (sweating and panting). During
without work, was not long enough to disrupt food
experiment 2, both working and non-working oxen
intake or feeding behaviour. Similarly, Pearson and
consumed similar amounts of water.
Water
Smith (1994) found no effect of food restriction for
consumption
during working periods included
4 h, with or without work on intake of straw diets by
water intake during days animals were not working.
cattle and buffalo.
This may have masked any short-term effect work
would have on water consumption.
However since
In experiment 2 food intake was significantly
plasma thyroid hormone concentrations were also
affected by the proportion of leaves in the stover and
similar in working and non-working periods, the
therefore by the quality of the diet. These
implication is that the extent of heat stress in animals
observations suggest that a strategy to improve
at-rest and in those working were similar in this
intake of these poor quality diets such as millet
experiment and water requirements may therefore
stover would be to increase the amount offered to the
have been similar also. In experiment 2, the higher
working animal, thus allowing greater selection of
heat load of working oxen, as compared with oxen
the more digestible components, to compensate for
at-rest, suggested by differences in thyroid hormone
the extra energy used for work.
concentrations, would have accounted for the
working oxen consuming significantly more water
The concept of additivity of hunger and satiety
than non-working oxen.
signais described by Forbes (1995) could at least
partly explain the absence of difference
or decrease
During experiment 1, DM1 of millet stover increased
in intake in working animals as compared with
as the experiment progressed. A similar pattern of
animals at-rest. When working animals are given
intake in working oxen was observed by Pearson
high roughage diets the negative signals generated
and Lawrence (1992). They reported increased food
from stretch receptors in the rumen activated by the
intake over time and suggested that animals were
distension caused by the high ce11 wall content of the
adapting to the food during the experiment. In the
diet could offset the intake stimulating signais
present study this adaptation did not enable oxen to
induced in tissues as a result of the depletion of
eat more than those at-rest or those working lightly,
energy substrates due to work. However, Faverdin et
since the overall food intake during the 3-week
nl., (1995) suggest that the negative feedback loop
experimental periods were similar for a11 work
where post-ingestive signals depress the motivation
treatments during experiment 1. Similarly, during
to eat is acceptable to describe the short-term feeding
experiment 2, work did not have a significant effect
patterns of ruminants. They suggested that the
on intake of millet stover.
long-term regulation of food intake is of significance
224
Fall, Pearson, Lawrence and Fernandez-Rivera
in animal production and that this is driven by the
during working periods oxen were catabolizing
energy requirements and the body reserves of the
amino acids to supply energy-yielding substrates for
animal. The increase of food intake over time seen in
work.
this study supports the concept of the long-term
regulation of food intake. Increases in food intake
were also reported by Zerbini et nl. (1995) in draught
Although the rate of passage of undigested food
cows working intermittently over a long period of
residues tended to increase with light work, oxen
time (90 days). The long-term increased energy
given low quality trop residues could neither
requirements for lactation and work may have
increase their food intake nor use food more
caused increases in food intake in these CO~S.
efficiently to compensate for the extra energy used
for work. Therefore they mobilized their body
In this study, DM apparent digestibility and the
reserves to supply energy to working muscles. Hence
apparent digestibility of food fractions were not
weight loss is a constant feature in working oxen
significantly affected by work. These results agree
relying on roughages for energy intake. Oxen could
with those reported by several others (see Pearson
maintain their weight during resting periods when
and Dijkman, 1994). In the present study, a
they were given sufficient millet stover SO that they
significant
improvement i n
f o o d
apparent
could Select leaves which were more nutritious. Heat
digestibility was observed as the proportion of leaves
stress on oxen did net interferc with their digestive
in the millet stover increased and therefore as the
physiology. The implications of these results for the
quality of the diet improved. Hence differences in
formulation of feeding strategies for draught oxen in
diet quality may well have contributed to the
semi-arid areas include the following considerations.
different responses in apparent digestibility of food
First, since work and heat stress did not influence
seen in working oxen .
intake and digestibility of foods, it may be relevant to
predict food intake of these animals using models
Rate-constants k, and k, representing the rate of
developed for other classes of cattle. Secondly, ways
passage of digesta through the rumen and the lower
to increase intake of roughages in semi-arid areas
tract, respectively, were not affected by work. This
must be sought. Treatments of trop residues and the
agrees with results reported by Zerbini c’f nl. (1995)
supplementation of these roughages with highly
who did not find significant differences in passage
digestible forages supplying rumen degradable and
rate of Cr-mordanted hay between working and
rumen undegradable nutrients must be considered.
non-working CO~S. However, MRT of solid particles
Where trop residues are abundant, oxen should be
in the digestive tract was less for oxen working
given excess residues to increase their food intake.
2.5 h/dav than for animals at-rest or working 5 h/
Finally, since oxen cannot increase their nutrient
day. This suggests that light exercise may have
intake during work when given trop residues and
caused more rapid rate of passage of foods in the
therefore use their body reserves to perform work,
digestive tract.
the effect of body condition on work output should
be investigated.
During experiment 1, oxen at-rest were able to gain
weight whereas oxen working 2 h/day maintained
their M. During experiment 2, oxen at rest
maintained their weight while oxen working 2.5 or
Acknowledgements
5 h day lost weight. The energy intake from millet
T h e
authors
thank
the Overseas
Delrelopment
stover and concentrate (21.3 g DM per kg Mo’75
Administration (ODA) of the United Kingdom and the
during experiment 2) was sufficient to allow weight
International Livestock Rcsearch Institute for funding this
gains in oxen at-rest. During experiment 2, thc level
study and E. A. Hunter for statistical advice during
of concentrate offered was lower (1Og DM per kg
preparation of the manuscript.
M”.75), but the animais had opportunities to Select
more leaves from the millet stover which was given
in excess (0.50) of appetite. During experiment 1,
energy requirements for work could be met by intake
References
when animals worked 2 h/day, ensuring the
Association of Officia1 Analytical Chemists. 1990. offiicial
maintenance of weight in these animals. The weight
n~thods ~~~n~znl~~sis, 15th ed. Association of Officia1 Analytical
losses seen i n o x e n w o r k i n g 4 h/day during
Chemists, Arlington, Virginia.
experiment 1 and in animals working 2.5 or 5 h/day
Bakrie, B. and Teleni, E. 1991. The effect of time of feeding
during
experiment 2 illustrated that cnergy
in relation to work on draught nnimals. 1. The effect of
requirements could not be met from intake alone. In
feeding hil;h fibl-e diet rilher before or dfter work «n feed
both experiments there was a linear increase in PUN
utilisation nnd physiology of working buffaloes. Dnlfl‘#f
as the work level increased. This suggested that
Arlitfral Bldkfitl 1: 39-35.
Nutrition of draught cattle - 2
225
Bakrie, M., Murray, R. M. and Hogan, J. P. 1988. The cffect
contrasting diets and housed at 20 and 33°C. \\ourrfnl ot
of work on intake and rumina1 fluid, volatile fatty acid and
A~qric~rhrrnl Srimcr, Cmbridgc 113: 211-222.
NH, concentration of steers fed Rhodes grass hay. DAP
Matthewman, R. W. and Dijkman, J. T. 1993. The nutrition
Pruj~t Bulletin 8: 23-26.
of ruminant draught animals. ]owml #Agricultnral Sci~me,
Bamualim, A. and Ffoulkes, D. 1988. Effect of work and
Cnrvbridgr 121: 297-306.
level of feeding intake on nutritional parameters and
Pearson, R. A. and Archibald, R. F. 1990. Effect of ambient
bodyweight change of swamp buffalo cows. DAP Projet
temperature and urea supplementation on the intake and
8ldhTfiJl 7: 2-7.
digestion of alkali-treated straw by Brahman cattle and
Christopherson, R. J. and Kennedy, P. M. 1983. Effect of
Swamp buffaloes. journal of A#x/ttwnl S&IC~, Cnmbridgc
the thermal environment on digestion in ruminants.
114: 177-186.
Cm7ndim ]ournn/ $R~~ind Sciencr 63: 477-496.
Pearson R. A. and Dijkman, J. T. 1994. Nutritional
Collier, R. J. and Beede, D. K. 1985. Thermal stress as a
implications of work in draught animais. Proceedings of the
factor a s s o c i a t e d w i t h nutrient r e q u i r e m e n t s a n d
Nutrition Society 53: 169-179.
interrelationships. ln Nufrifim qfgrming rfminnf~fs
irf wariif
Pearson, R. A. and Lawrence, P. R. 1992. Intake, digestion,
cliaznf~s (cd. L. R. McDowell), pp. 59-71. Academic Press,
gastrointestinal
transit time and nitrogen balance in
London.
working oxen: studies in Costa Rica and Nepal. Anirml
El-Nouty, F. D. and Hassan, G. A. 1983. Thyroid hormone
Prodncfim 55: 361-370.
status and water metabolism in Hereford cows exposed to
Pearson, R. A. and Smith, D. G. 1993. The effects of work
high ambient temperature and water deprivation. 1r1dinrl
on food intake and ingestive behaviour of draught cattle
/ouvu 0fArliml Scierfcc 53: 807412.
and buffalo given barley straw. At~ivml Producfim 58:
Faverdin, P., Baumont, R. and Ingvartsen, K. L. 1995.
339-346.
Control and prediction of feed intake in ruminants. In
Preston, T. R. and Leng, R. A. 1987. M&chirrg runrirmt
Rmwt d~z~clopn~ts il7 fhr nrrtrition o f lwbizwn ( e d . M .
producfim systems reifll mnilnbk reswrccs irl fhc fropics mrd
Journet, E. Grenet, M.-H. Farce, M. Theriez and C.
wb-tropics. Penambul Books, Armidale, Australia.
D e m a r q u i l l y ) . Proccedings of fh ,fourth interrzntima/
synposium OH the rzufrifion of 1wrbioorw pp. 95-120. INRA
Statistical Analysis Systems Institute. 1985. SAS mers
Editions, Paris.
guide: sfntisfics. Statistical Analysis Systems Institute Inc.,
Cary, NC.
Forbes, J. M. 1995. Vohtnry food intakc nrzd dict sclrctiorz in
Weston, R. H. 1985. Some considerations of voluntary feed
,fnrl?r animnls. CAB International, Wallingford.
consumption and digestion in relation to work. In Drnught
Grovum, W. L. and Williams, V. J. 1973. Rate of passage of
n~rirrlnl poxwfor productim (ed. J. W. Copland). Proceedings of
digesta in sheep. 4. Passage of marker through the
un it~turzntionnl
zuorkshoy, ]ntnes Cook Lhizmity, Tozmsz~illt~,
alimentary tract
a n d t h e b i o l o g i c a l relevance o f
Ausfrnlin, 10-16 ]uly 3985. ACIAR proceeding series no. 10,
rate-constants derived from the changes in concentration of
pp. 78-83. ACIAR, Canberra.
marker in faeces. British @mn/ ofh’utritiorr 30: 313-329.
Zerbini, E., Gemeda, T., Wold, A. G., Nokoe, S. and
Lawrence, P. R. and Pearson, R. A. 1985. Factors affecting
Demissie, D. 1995. Effect of draught work on performance
the measurement of draught force, work output and power
and metabolism of crossbred CO~S. 2. Effect of work on
of oxen. ]ourrml of Agricultural Sciencr, Cnmbric@ 105:
roughage intake, digestion, digesta kinetics and plasma
703-714.
metabolites. Arzimnl Scimce 60: 369-378.
Mathers, J. C., Baber, R. P. and Archibald, R. F. 1989.
Intake, digestion and gastro-intestinal mean retention time
in Asiatic buffaloes and Ayrshire cattle given two
(Rmizvd 29 ]annunry 1996~Acrepted 13 S@mber 1996)
on intake, apparent digestibility and rate of passage of food through
the gastro-intestinal tract in draught oxen given trop residues
A. Fall’, R. A. Pearson’, P. R. Lawrence’t ad S. Fernhndez-Rivera2
Abstract
Tzu0 exprrinmfs zucre condwfcd fo irizmfigafr fhe wlnfionshi}~s befïuccu roork and iufnke 171zd digesfioll qff~oli [y
draughf oxm gizle~z millet Sfo7Jt’r. Irz fhefiusf experimwf, infnke qf nlil/et sfovu, zvaf-CY iufake, livc 7urigltf, plasnla
conccnfmfions of fviiodofhyvonine, fhyroxine mid wca-nifuogw 7uere measured irz 28 nnirnals fhaf workcd 0, 2 01
4 h/day if7 seq~zce during fhrer 3-nwk experinmtal periods. Digcsfibilify and rate $ passnge of.food rcsidzres
tl~rough fhe digcstizle tract W~YP measwed in a second rxperimcrzt on 12 aninzals 7uorki~1~ rifle 0, 2.5 or 5 Il/clny h
scquence during fhrer 2-zueek expeuimn tal periods. Ferding behaviow zvas monifored on six a~~inrals workirlg
eitkcr 0, 2.5 OY 5 h/day. Work did nef @xf infakc of millet stowr, apparent digesfibilifirs arld fhe rate of pmsqe qf
digesta fhro7@ fhc gastro-i!zfcstinal tract. This suggests thaf fhr nutrient supply fiom intake qf rorq,dqes bly
zuorkiny o.xen is mlikcl~/ to be sufficicnt to compensatefor the extra energy expended durirzg work. Food iflfake 711175
aficted by fkr quality Cl$ the millet stozw offered. Thr level of intake (If millet stozw was proportiorml to tire anlount
of leazles in fhe sfover. Foo[f irztake increased also 05 zuork progressed. Howczw, a~~inzals nzobili,-rd their body
reserves fo perfom zoork. Anirnals commed ~OYC mater m mrking days than olz dnys they WCYC af-rest in shadr.
The heaf stress fhaf zuorking animais we~e subjectcd fo did mt appenr fo iizferfere 7uith flwir di~l~sfizlr.flrnctioll.
Keywords: digestibility, draughf aninzals, food intakc, millet stozw, 7oork.
Introduction
to the depletion of circulating energy substrates.
Ideally, draught oxen must consume sufficient food
With
sustained
exercise,
muscles
draw
before and during the cropping season SO they cari
energy-yielding substrates from body reserves. Work
start work with a reasonabie live weight and perform
therefore imposes a higher energy demand, which
work. However the scarcity and poor quality of
would be expected to stimulate intake to supply
foods available before and during the early part of
energy to muscle and to replenish depleted body
the cropping season in semi-arid areas often limit
nutrients (Weston, 1985). The occurrence of fatigue is
their nutrient intake. Food intake cari be influenced
a natural result of sustained muscular activity. The
positively or negatively by work through direct or
desire to eat and ruminate may be suppressed by
indirect mechanisms. Direct effects of work on food
fatigue (Pearson and Lawrence, 1992). Physiological
intake occur through physiological changes resulting
changes in working animals also include increased
from exercise. Muscular activity induces a higher
body temperature due to heat gained from solar
metabolic rate in working animals as compared with
radiation and increased metabolism during work.
animals at-rest (Preston and Leng, 1987). This leads
The resulting heat stress could depress food intake in
working animals (Collier and Beede, 1985).
t Present address: Centre for Agriculture in the Tropics
One indirect effect of work on intake stems from the
and Subtropics.
Institute o f A n i m a l
Production,
reduced time animals have access to food. Limited
Department
of Animal Nutrition
a n d Aquaculture.
time available to eat and ruminate is a major
üniversitkit Hohenheim (MO), D-7093, Stuttgart, Germany.
constraint to increased food intake in working
217
238
Fall, Pearson, Lawrence and Fernhdez-:Rivera
ruminants (Pearson and Lawrence, 1992). Time of
feeding also affects food intake. Bakrie and Telcni
(lY91) reported reduccd f o o d i n t a k e by animals
given roughages beforc work as compared with
animals given food aftcr work.
Work also has the potential to affect digestibility of
foods by oxen directly and indirectly through
Dry matter (DM) (g/kg)
902
Y40
90s
935
changes in a range of factors including increases in
Cru& orotein CCP)
33
36
293
177
body temperature, food particle residence time in the
C;ross ;nergy (C;E<)’
gastro-intestinal
tract
a n d
effectiveness of
(MJ/kg DM)
1 ï.5
18.0
15.1
14.7
mastication on particle breakdown (Weston, 1985).
Organic math%r (OM)
Y64
Y73
898
ïF>h
Positive effects of work on food digestibility may
Neutral-detcr#ent
fibre (NDF)
789
781
293
1 9 7
s tem
f r o m t h e
cnhanccment
o f
microbial
Acid-detcrgent fibre (ADF) 539
519
131
7 2
fermentation though greater mixing of rumen
Hemicelluk~sr~ (HEM)
273
2 6 1
162
125
contents due to exercise (Matthewman and Dijkman,
1993) and higher but moderate body temperatures
resulting from work. Dctrimental effects of work on
food digestibility may result from the shift of blood
16.00 and 18.OD h. Food trnughs and buckets were
flow from the gut to muscles and peripheral tissues,
withdrawn from a11 the yens when oxen on exercise
reduction in meal frequencies (Matthewman and
schedule were working. Therefore a11 animais had
Dijkman, 19Y3), and the less thorough mastication of
equal time o f ilccess to food, but assuming work
food because of limited timc to ruminate (T’earson
restricted rumination, they did net have similar time
a n d S m i t h , 1 9 9 4 ) . T h e r e i s n e e d f o r ‘3 c l e a r
available to ruminate. Orts were regularly removed
understanding of the relation between work and
from troughs. Oxen at rest wcre tethered out of the
digestive physiology for the feeding management of
yens and in direct sunlight when other teams tvere
draught oxen
t o b e i m p r o v e d . T h i s s t u d y
working.
investigated the relationships between food intake
and the efficiencv of utilization of foods and work
EsprGrrrlfnl ilcz&. A Latin-square cross-o\\‘er des@
p e r f o r m a n c e . .
w i t h r e p e a t e d measures was a d o p t e d f o r t h i s
experiment. Treatment consisted of the number of
hours worked per day: 0, 2 and 4 h/day pulling a
Material and methods
loaded sledge along a flat circuit or performing
E.qx?rin1en
t 1
common field operations (cultivation). Oxen were
A~iininls a{?~1 fi~di~. This experiment was conducted
allotted according to their initial body weight in
from July to September 1993 at the International
three groups with average weights of 245, 273, and
Livestock Research Institute (ILRI), International
390 kg for groups 1, 2 and 3, respectively. Oxen in
Crop Research Institute for the Semi-Arid ‘Tropics
groups 1, 2 and 3 were allotted to squares 1, 2 and 3,
(ICRISAT) Sahelian Centre, Sadore, Niger. Eighteen
respectively SO that each square was formed with
local zebu oxen, aged 4 to 8 years, average live
animais of similar live weight. Rows of each square
weight 302 (s.e. 18) kg, were used. Oxen were housed
w e r e formed b y o x teams w h e r e a s c o l u m n s
in individual concrete-floored pens roofed with zinc
represented experimental periods. The experiment
sheets. Each pen was fitted with a halved empty oil
lasted 9 weeks, which was divided into three 3-week
drum as a food trough and a graduated metal bucket
periods. Treatments were applied in sequence to
for water. Individual pens were separated with
t e a m s during experimental p e r i o d s . During each
wooden planks to prevent mixing of food and food
period, three teams were idle, three teams were
spillages.
working 2 h/day and three tcams were working
4 h/day. Each team worked 3 dayslweek. Teams
Oxen were trained to pull common farm impletnents
working for 4 h/day worked 2 h in the morning and
and 55-kg metal sledges. They were given chopped
2 h in the afternoon.
millet stover nd libitw except during the working
periods. Millet stover was supplemented with a
Mcnst~uerw~~fs.
Work output, distance travelled and
concentrate mix made LIP (g/kg) of wheat bran (600),
elapsed working time were continuously measured
groundnut cake (300) and bone meal (100) at a rate of
using an ergonieter (Lawrence and Pearson, 1985).
21.3 g/kg M”.” per day (Table 1). The concentrate
W e e k l y b l o o d s a m p l e s w e r e t a k e n f o r t h e
was offered when animais rcturncd from work in the
determination of plasma urea-N (PUN), thyroxine
morning at about 11.00 h. Millet stover was given
(T,) and triiodothyronine (T,). Body weight was
when oxen finished eating the concentrate, and at
measured every week. Food offered and refusals
Nutrition of draught cattle - 2
219
were weighed every day. Refusals on the floor and
Expcrirnent 2
food left in troughs were collected separately
Anin& and feeding. This experiment was conducted
because of contamination of floor spillage by urine
from December 1994 to February 1995 at the
and water.
ICRISAT Sahelian Centre in Niger. Twelve oxen,
aged 4 to 7 years, average weight 288 (s.e. 11) kg, at
Lnbountq nnalysis. Daily fond samples were pooled
the start of the experiment, were used. They were
each week. A sample was taken and dried in a forced
housed as in experiment 1. Al1 oxen were given
air-oven to constant weight at 55°C and ground to
chopped millet stover nd libitum except during the
pass a l-mm screen. The following determinations
working hours. The stover was chopped by hand to
were made on the weekly pooled samples of foods:
lengths of about 12 to 20 cm. The millet stover was
acid-detergent fibre (ADF), neutral-detergent fibre
supplemented with a concentrate mix made up (g/
(NDF), nitrogen (N) gross energy (GE), ash and
kg) of wheat bran (400), groundnut cake (300), rock
organic matter (OM) according to the Association of
phosphate (lOO), crushed bone (100) and common
Officia1 Analytical Chemists (1990).
salt (100) (Table 1). The concentrate was given at a
daily rate of 10 g dry matter per M0.75 at 12.00 h after
Plasma T, was analysed using the fluorescence
the morning working session. Daily food allowance
polarization immunoassay technique with an Ahbot
was adjusted SO that refusals were at least equal to a
‘TDx Analyser (Abbot Laboratories, USA). The
proportion of 0.50 of food offered.
analysis for plasma T, used the IMx total T; assay
based on the microparticle enzyme immunoassay
Trcafmcnts. Treatments consisted of levels of work
technique (Abbot Laboratories, USA). !?UN was
performed: 0, 2.5 and 5 h/day achieved by walking
assayed by an enzymatic method using a Bayer
0, 6 and 12 km/day, respectively. Each team in an
Diagnostic RA-2000 random access chemistry
exercise treatment pulled a metal sledge loaded with
analyser (Bayer Diagnostics, Basingstoke, UK).
weights SO that the draught force exerted was
equivalent to proportionately 0.10 of the team live
D&l arlnl~lsis. The following statistical mode1 was
weight. Work was performed continuously, 7 days/
used to analyse food and water intake, weight
week, pulling the sledge around a flat circuit. Work
change, plasma thyroid hormones and PUN
stopped when the set distance or set time was
concentrations:
completed or when one of the oxen in the team was
unwilling to continue.
Experimental des@. A Latin-square crossover design
was used. Twelve oxen were assigned to the three
where: Y = dependent variable (food intake, water
treatment groups, two teams in each group. The
intake,
M change, plasma thyroid hormones
rows of the squares represented individual oxen,
concentration, urea-nitrogen concentration); p =
whereas columns were experimental periods. The
overall mean; S, = effect of ith square, i = 1, 2, 3;
experiment lasted 10 weeks divided into five 2-week
T(S),,,, = effect of the jth team nested within ith
periods. Observations were repeated every week in
s q u a r e , i = 1,2,3; PCS),,,, = effect o f t h e k t h
periods 1, 3 and 5. No treatment was applied during
experimental period nested within ith square, k =
periods 2 and 4 to dissipate carry-over
effects from
1,2,3; AcI, = effect of the Ith work level, 1 = 1: 0 h/
previous periods. Each square included oxen of
day, 1 = 2: 2 h/day and 1 = 3: 3 h/day; PV,,, = effect of
similar live weight. Treatments were applied in
the rnth week, m = 1,2,3; W X Plllli = interaction
seyuence during experimental periods SO that during
between the nzth week and the kth period; W X A,,,, =
each period four oxen were idle, four oxen were
interaction between the mth week and the lth work
working 2.5 h/day and four oxen were working 5 h/
level; W X T(Sjci,,,,, = interaction between the mth
day.
week and the jth team in the ith square; Eiikl,ri = effect
peculiar to the jth team in the ith square subjected to
Mensuwmenfs.
Sampling,
measurements
a n d
the Ith level of work in nzth week of the kth period.
laboratory analyses were as in experiment 1 with the
following amendments and additions.
The term T(S),,,, was used as the error term to test the
effect of work. The sums of squares for treatment
Work: an ergometer was used only during the
and week were further partitioned into single
preparation phase of this experiment, to measure
degrees of freedom using polynomial contrasts (i.e.
work performed, distance travelled and elapsed
A,). Weekly live-weight changes were estimated by
working time for different known work loads. A
regression analysis and were further subjected to
regression analysis of force on work load was
analysis of variante using generalized linear models
derived and used to determine the load required for
(Statistical Analysis Systems Institute (SAS), 1985).
each team SO that the draught force exerted was
220
Fall, Pearson, Lawrence and Fernandez-Rivera
equivalent to proportionatelv 0.10 of the team live
water intake, M change, plasma thyroid hormones
weight The time taken to travel around the circuit
and PUN concentrations included as main factors:
was measured with a stop watch.
square, ox nested within square, experimental period
nested within square, treatment (number of hours
lntnke nnd appamt digestibility qf food: each day a
worked), week and the interactions between these
sample of millet stover was taken before chopping
terms. Sources of variation for the analysis of
the stover. At the end of each week the daily millet
apparent digestibility coefficients were: square, ox
stover samples were pooled and plant parts were
nested within square, period nested within square
separated and weighed to determine proportion of
and treatment.
leaves in the stover.
Orthogonal linear and quadratic polynomials were
Three digestibility trials were conducted, one in each
used to test the effect of treatment. A regression
2-week period. Total faecal collection was carried out
analysis of dry matter intake (DMJ) and dry-matter
for 7-day periods using faecal bags harnessed to oxen
apparent digestibility (DMD) on the proportion of
throughout the collection period. The faecal bags
leaf in the stover was performed. Sources of variation
were emptied regularly and the faeces weighed and
for the analysis of time spent eating and ruminating,
placed into a bucket, stored in a cool place. At the
were treatment, oxen within treatment and time of
end of each day, faeces were mixed and a sample
observation.
(proportionately 0.05) was taken and frozen. At the
end of each 7-day collection period, daily samples
were thawed, mixed and a subsample (1 kg) was
taken and oven dried at 55°C.
Results
Expcrinrent 2
Rate
of passage
of food:
sixty grams of
Minimum,
maximum
a n d
mean
ambient
chromium-mordanted fibre were given on dny 7 of
temperatures were 23.0, 35.0 and 29.3”C when
the first and the second periods (Mathers et a/., 1989).
animals worked in the morning and 23.0, 36.0 and
On that day food was withdrawn from 14.00 until
31.7”C when work took place in the afternoon.
23.00 h when the markers were given. Faecal samples
Minimum, maximum and mean relative humidities
were collected at regular intervals as follows: 9,11,13,
were 0,400, 0.930 and 0.674 during the morning
15,17,19,21,24,33,37,39,41,43,47,57,61,65,
71,81,
working sessions and 0.440, 0.960 and 0.600 during
85,89,95,105,109,113,119,129,137,153,l61,177
and
the afternoon working sessions.
185 h after dosing. lndividual faecal samples were
thoroughly mixed and a sample was taken for the
Plasma T, and T, concentrations were not affected by
determination of dry matter and Cr concentration.
level of work (Table 2). There was a significant linear
Gastro-intestinal mean retention time was estimated
increase in PUN as level of work increased (P < 0.01;
using Grovum and Williams (1973) mathematical
Table 2).
procedures,
after a single dose of marker.
Daily DM1 of millet stover was not affected by
Feeding beknaiour: s i x o x e n , t w o o x e n i n each
number of hours worked per day. There was a
treatment group, were selected for the observation of
significant linear increase over the weeks in daily
feeding behaviour during the first period of the
DM1 expressed in kg DM (P < O.Ol), in g DM per kg
experiment. The behaviour of each animal was
M”.7i (P < 0.01) and in g DM per kg M (P < 0.05). The
monitored during a 3-h observation period every 5
interaction between treatment and week was
min. Two or three 3-h observation sessions were
significant for DMI-g/kg M and close to significance
carried out each day. At the end of the 4th day, the
at the 5% probability level (P = 0.07) for DMI-g/kg
combination of the 3-h observation periods yielded a
M”‘?“. Table 2 shows daily work characteristics, food
24-h composite behaviour pattern of the animais.
and water intake and weekly live-weight changes.
This scheme was applied three times consecutively.
Food intakes of animais working 2 and 4 h/day
During each 5-min observation period each of the six
include food consumption
on non-working and
animais was observed. The time spent doing a
working days. High intensities of work (4 h/day)
particular activity (eating, ruminating, standing,
depressed intake in working oxen during the first
lying) was estimated as the product of the number of
days of work. However, these animais were able to
tomes this activity was observed and the interval
increase their intake the following days such that
between observations (5 min).
they could eat as much as oxen at rest or oxen
working lightly.
Sfatistical aualysis. Data werc analysed using SAS
GLM procedures (SAS, 1985). The statistical mode1
There were no significant differences
due to work in
used to analyse daily intake of millet stover, daily
water consumption
expressed in I/day, l/kg M, l/kg
Work level
Variables
0 h/day
2 h/day
4 h/day
Significance
Work characteristics
Daily work output (kJ)
3233
(0.22)t
6763
(0.33)
Load (N/kg M)
0.89 (0.26)
0.88 (0.23)
Power (W)
583
(0.11)
616
(0.10)
Power (W/lOO kg)
Y0 (0.28)
92 (0.18)
Mean
s.e.
Mean
5.e.
Mean
s.e.
Daily intake of millet stover
k g D M
4.72
cl.045
4.78
0.049
4.60
0.049
g DM/kg M
15.46
0.17
15.94
0.19
15.50
0.19
g DM/ kg M’),7i
64.40
0.65
66.06
0.72
64.04
0.72
Daily water intake
litre (1)
30.5
0.47
30.2
0.51
30.3
0.51
b’kg M
0.099
0.001
0.099
0.002
0.101
0.002
1 /kg Ml’.”
0.41
0,007
0.42
Od~O8
0.42
0.008
l/kg DM1
6.45
0.09
6.32
0.09
6.58
0.09
T, (nmol/l)
56.3
1.2
52.7
1.2
52.3
1.2
T, (nmol/l)
0.95
0.03
0.94
0.03
0.98
0.03
PUN (mmol/l)
4.0
1.14
4.5
0.14
4.83
0.14
LineaP
Live-weight change (kg/week)
3.72
0.76
1.58
0.84
-2.19
0.82
*
t Values in parentheses are CVs.
M0-7i or l/kg DM1 (Table 2). In this experiment, oxen
DM1 (g/kg M@75) = 52.5 (se. 4.44) + 20.8 (se. 7.65) X PLS
at-rest were tethered in the suri while other teams
(P < 0.01; R’ = 0.28).
were working. Body-weight change was significantly
affected by work (P < 0.05; Table 2).
Table 3 Experimmt 2: lenst-squnré mms for infake of millet
stowr, watrr intake, liue zueight sud plasma concm tration of urea
Expriment 2
rzifrogm (PLIN) ofoxen zuorking 0,2,5 atzd 5 h/day
There was a significant linear increase in PUN
concentration as work level increased (P < 0.05; Table
Work level
3). The effects of week and the interaction between
0 h/day
25 h/day 5 h/day
St.
work level and week were also significant
(P < 0.001). Increases of PUN over weeks were
Intake of
greatest as work level increased.
millet stover
dkg M
1 5 . 1 3
16.22
16.15
0.20
Plasma TJ concentration decreased as work Ievel
g/kg M”,i5
61.36
65.82
65.51
0.83
increased (Table 4). There was a significant linear
Water intake
decrease (P < 0.01) in plasma T, concentrations as
I/day
21.35"
25.20h
28.51c
0,380
work load increased and over weeks (P < 0.001).
l/kg M
0.08"
0.09"
0.11'
0.014
I/kg M”,7”
0.32"
0.3Bh
0.43c
0.050
l/kg DM1
5.37"
5,83b
6.44'
0.120
Intake of millet stover was not significantly
PUN (mmol/l)t
influenced by work. Table 3 shows mean DMI, water
Before work
4.37
3.68
3.90
0.31
intake and live weight over 2-week experimental
W e e k 1
3.02
3.42
4.30
0.31
periods for oxen working 0, 2.5 and 5 h/day. The
Week 2
3.17
4.53
5.78
0.31
relationship between intake and the proportion of
Live weight (kg)t
leaf in the stover (PLS) is described by the following
Week 1
597
610
615
3
regression equations that show an improvement in
W e e k 2
599
602
597
3
food intake as the proportion of leaves increased:
t See text for the significance of factors (work and week)
included in the analysis of variante.
DM1 (g/kg M) = 12.8 (s.e. 1.09) + 5.4 (se. 1.18) X PLS
a,h.c Values in the same row with different superscripts are
(P < 0.01; R2 = 0.30)
significantly different P < 0.05.
--
--
.- _-~
222
Fall, Pearson, Lawrence and Fernhdez-Rivera
Apparent digestibilityt
DM
0.42
043
OI3
0.011
OM
0.45
046
0.45
0,012
ADF
0.54
0.54
0.55
0.010
NDF
0.57
0.57
0.58
0.009
HEM
0.63
0.63
0.65
0.009
G E
049
04
0.51
0~009
T4 (nmol/l)S
Before work
48.6
45.3
48.0
2.6
Week 1
49.0
444
38.7
2.6
Week 2
45.5
34.6
27.7
2.6
T, (nmol/l)$
Before work
0.77
0.69
0.64
0.04
Weck 1
0.69
OdA
062
04~4
Week 2
0450
04
0.39
ool
Time spent eating (min/day)
375
385
455
45
Time spent ruminating (min/day)
339
400
344
4 2
Time spent eating and ruminating (min/day)
715
785
799
49
Eating rate (g DM1 per min)
14.l
10.9
15.3
2.h
Rumination rate (min/g DMI)
88.3
108.1
78.7
10.5
MRT (h)
88.9
78.2
82.2
2.3
Quadratic ’
TT 04
14.17
14.54
13.28
14
llk,
56.9
49.1
52.3
2.8
llk,
17.9
14.6
16.6
1.2
t For abbreviations see Table 1.
$ See text for the significance of factors (work and weeks) included in the analysis of variante.
There was a significant increase in water intake as
HEMD = 0.14 (se. 0.05) + 0.87 (se. 0.09) X PLS
work level increased (Table 3). Work caused
(P < 0.01, R’ = 0.72)
live-weight losses whereas oxen at-rest were able to
maintain their body weight (Table 3).
GED = 0.12 (se. 0.04) + 0.67 (s.e. 0.08) X PLS
(P < 0.01, X2 = 0.66).
There was no significant effect of work on the
apparent digestibility of DM, OM, ADF, NDF,
The estimated values for the two rate constants (k,,
hemicellulose (HEM) and GE. Table 4 shows
k2), the calculated time of first appearance of marker
coefficients of apparent digestibility for diiferent
in faeces (TT) and the mean retention time (MRT) are
work loads. Increases in the proportion of leaves in
shown in Table 4 for Cr-fibre. The rate constants k,
the food offered improved apparent digestibility
and k2 refer to the proportion of matter leaving the
coeffficients
as illustrated by the regression o f
rumen and the large intestine, respectively. Their
apparent digestibility coefficients on PLS given in the
reciprocals represent the retention time in each pool
following equations:
(Grovum and Williams, 1973). Work did not
significantly influence TT, k, and kT However, the
DMD = 0.03 (se. 0.08) + 0.69 (s.e. 0.08) X PIS
quadratic effect of work on MRT was significant
(P < 0.01, R2 = 0.68)
(P < 0.05). Work did not significantly affect time
spent eating and
ruminating or eating and
ADFD = 0.25 (se. 0.04) + 0.52 (se. 0.08) X PIS
rumination rates (Table 4).
(P < 0.01, R2 = 0.52)
NDFD = 0.19 (se. 0.04) + 0.68 (se. 0.08) X PIS
Discussion
(P < 0.01, R2 = 0.69 )
In experiment 1 there was an absence of significant
differenccs in plasma T, and T, concentrations
OMD = 0.06 (se. 0.05) + 0.70 (se. 0.09) X PIS
between working oxen and oxen at-rest. However in
(P < 0.01, R2 = 0.65)
experiment 2, the higher the work load, the greater
Nutrition of draught cattle - 2
223
was the decrease in plasma T, and T,. Decreases in
Most results show little difference
in intake in
plasma T7 and T, concentrations as a response to heat
working animals compared with animals at-rest
stress were reported by Pearson and Archibald
(reviewed by Pearson and Dijkman, 1994). The
(1990) and El-Nouty and Hassan (1983). During
absence of an effect of work on food intake when
experiment 2, unlike experiment 1, oxen at-rest were
time of access to food was standardized, as in this
not exposed to solar radiation and ambient
study, was reported by Pearson and Lawrence (1992)
temperatures were lower. Differences
in heat stress
and Pearson and Smith (1994) in cattle and by
between working and non-working oxen were great
Bamualim and Ffoulkes (1988) and Bakrie cf nl. (1988)
enough to induce significant differences in plasma
in buffaloes.
concentrations of T, and T, between the groups.
The effect of work on food intake may result from
The higher heat load of working oxen during
the work stress and/or from the food restriction
experiment 2 relative to oxen at rest did not translate
during hours animals work (Pearson and Smith,
into significant changes in food intake and
1994). In the present study oxen at-rest and working
digestibility. Christopherson and Kennedy (1983)
oxen had equal time available to eat. It was assumed
suggest that extremes of heat or cold are needed
that oxen at-rest had more opportunities to ruminate
before marked differences in digestibility are seen. It
than working oxen because oxen rarely ruminate
is also probable that animals used in these
when they work. Since food intake was not
experiments, being born in the area, were well
significantly different between working and
adapted to high ambient temperatures.
non-working oxen during both experiments, then the
limited time available to ruminate may not have
Although little quantitative information is available,
been a significant inhibitor of food intake in working
it is generally assumed that oxen need to consume
oxen in these experiments. Results in experiment 2
more water during working days as compared with
showed the time spent eating and ruminating was
non-working days, particularly under hot conditions
similar whether animals worked 0, 2.5 or 5 h/day.
to compensate for water lost through evaporative
Clearly, a 5-h period of food deprivation, with or
cooling processes (sweating and panting). During
without work, was not long enough to disrupt food
experiment 2, both working and non-working oxen
intake or feeding behaviour. Similarly, Pearson and
consumed similar amounts of water.
Water
Smith (1994) found no effect of food restriction for
consumption
during working periods included
4 h, with or without work on intake of straw diets by
water intake during days animals were not working.
cattle and buffalo.
This may have masked any short-term effect work
would have on water consumption.
However since
In experiment 2 food intake was significantly
plasma thyroid hormone concentrations were also
affected by the proportion of leaves in the stover and
similar in working and non-working periods, the
therefore by the quality of the diet. These
implication is that the extent of heat stress in animals
observations suggest that a strategy to improve
at-rest and in those working were similar in this
intake of these poor quality diets such as millet
experiment and water requirements may therefore
stover would be to increase the amount offered to the
have been similar also. In experiment 2, the higher
working animal, thus allowing greater selection of
heat load of working oxen, as compared with oxen
the more digestible components, to compensate for
at-rest, suggested by differences in thyroid hormone
the extra energy used for work.
concentrations, would have accounted for the
working oxen consuming significantly more water
The concept of additivity of hunger and satiety
than non-working oxen.
signais described by Forbes (1995) could at least
partly explain the absence of difference
or decrease
During experiment 1, DM1 of millet stover increased
in intake in working animals as compared with
as the experiment progressed. A similar pattern of
animals at-rest. When working animals are given
intake in working oxen was observed by Pearson
high roughage diets the negative signals generated
and Lawrence (1992). They reported increased food
from stretch receptors in the rumen activated by the
intake over time and suggested that animals were
distension caused by the high ce11 wall content of the
adapting to the food during the experiment. In the
diet could offset the intake stimulating signais
present study this adaptation did not enable oxen to
induced in tissues as a result of the depletion of
eat more than those at-rest or those working lightly,
energy substrates due to work. However, Faverdin et
since the overall food intake during the 3-week
nl., (1995) suggest that the negative feedback loop
experimental periods were similar for a11 work
where post-ingestive signals depress the motivation
treatments during experiment 1. Similarly, during
to eat is acceptable to describe the short-term feeding
experiment 2, work did not have a significant effect
patterns of ruminants. They suggested that the
on intake of millet stover.
long-term regulation of food intake is of significance
224
Fall, Pearson, Lawrence and Fernandez-Rivera
in animal production and that this is driven by the
during working periods oxen were catabolizing
energy requirements and the body reserves of the
amino acids to supply energy-yielding substrates for
animal. The increase of food intake over time seen in
work.
this study supports the concept of the long-term
regulation of food intake. Increases in food intake
were also reported by Zerbini et nl. (1995) in draught
Although the rate of passage of undigested food
cows working intermittently over a long period of
residues tended to increase with light work, oxen
time (90 days). The long-term increased energy
given low quality trop residues could neither
requirements for lactation and work may have
increase their food intake nor use food more
caused increases in food intake in these CO~S.
efficiently to compensate for the extra energy used
for work. Therefore they mobilized their body
In this study, DM apparent digestibility and the
reserves to supply energy to working muscles. Hence
apparent digestibility of food fractions were not
weight loss is a constant feature in working oxen
significantly affected by work. These results agree
relying on roughages for energy intake. Oxen could
with those reported by several others (see Pearson
maintain their weight during resting periods when
and Dijkman, 1994). In the present study, a
they were given sufficient millet stover SO that they
significant
improvement i n
f o o d
apparent
could Select leaves which were more nutritious. Heat
digestibility was observed as the proportion of leaves
stress on oxen did net interferc with their digestive
in the millet stover increased and therefore as the
physiology. The implications of these results for the
quality of the diet improved. Hence differences in
formulation of feeding strategies for draught oxen in
diet quality may well have contributed to the
semi-arid areas include the following considerations.
different responses in apparent digestibility of food
First, since work and heat stress did not influence
seen in working oxen .
intake and digestibility of foods, it may be relevant to
predict food intake of these animals using models
Rate-constants k, and k, representing the rate of
developed for other classes of cattle. Secondly, ways
passage of digesta through the rumen and the lower
to increase intake of roughages in semi-arid areas
tract, respectively, were not affected by work. This
must be sought. Treatments of trop residues and the
agrees with results reported by Zerbini c’f nl. (1995)
supplementation of these roughages with highly
who did not find significant differences in passage
digestible forages supplying rumen degradable and
rate of Cr-mordanted hay between working and
rumen undegradable nutrients must be considered.
non-working CO~S. However, MRT of solid particles
Where trop residues are abundant, oxen should be
in the digestive tract was less for oxen working
given excess residues to increase their food intake.
2.5 h/dav than for animals at-rest or working 5 h/
Finally, since oxen cannot increase their nutrient
day. This suggests that light exercise may have
intake during work when given trop residues and
caused more rapid rate of passage of foods in the
therefore use their body reserves to perform work,
digestive tract.
the effect of body condition on work output should
be investigated.
During experiment 1, oxen at-rest were able to gain
weight whereas oxen working 2 h/day maintained
their M. During experiment 2, oxen at rest
maintained their weight while oxen working 2.5 or
Acknowledgements
5 h day lost weight. The energy intake from millet
T h e
authors
thank
the Overseas
Delrelopment
stover and concentrate (21.3 g DM per kg Mo’75
Administration (ODA) of the United Kingdom and the
during experiment 2) was sufficient to allow weight
International Livestock Rcsearch Institute for funding this
gains in oxen at-rest. During experiment 2, thc level
study and E. A. Hunter for statistical advice during
of concentrate offered was lower (1Og DM per kg
preparation of the manuscript.
M”.75), but the animais had opportunities to Select
more leaves from the millet stover which was given
in excess (0.50) of appetite. During experiment 1,
energy requirements for work could be met by intake
References
when animals worked 2 h/day, ensuring the
Association of Officia1 Analytical Chemists. 1990. offiicial
maintenance of weight in these animals. The weight
n~thods ~~~n~znl~~sis, 15th ed. Association of Officia1 Analytical
losses seen i n o x e n w o r k i n g 4 h/day during
Chemists, Arlington, Virginia.
experiment 1 and in animals working 2.5 or 5 h/day
Bakrie, B. and Teleni, E. 1991. The effect of time of feeding
during
experiment 2 illustrated that cnergy
in relation to work on draught nnimals. 1. The effect of
requirements could not be met from intake alone. In
feeding hil;h fibl-e diet rilher before or dfter work «n feed
both experiments there was a linear increase in PUN
utilisation nnd physiology of working buffaloes. Dnlfl‘#f
as the work level increased. This suggested that
Arlitfral Bldkfitl 1: 39-35.
Nutrition of draught cattle - 2
225
Bakrie, M., Murray, R. M. and Hogan, J. P. 1988. The cffect
contrasting diets and housed at 20 and 33°C. \\ourrfnl ot
of work on intake and rumina1 fluid, volatile fatty acid and
A~qric~rhrrnl Srimcr, Cmbridgc 113: 211-222.
NH, concentration of steers fed Rhodes grass hay. DAP
Matthewman, R. W. and Dijkman, J. T. 1993. The nutrition
Pruj~t Bulletin 8: 23-26.
of ruminant draught animals. ]owml #Agricultnral Sci~me,
Bamualim, A. and Ffoulkes, D. 1988. Effect of work and
Cnrvbridgr 121: 297-306.
level of feeding intake on nutritional parameters and
Pearson, R. A. and Archibald, R. F. 1990. Effect of ambient
bodyweight change of swamp buffalo cows. DAP Projet
temperature and urea supplementation on the intake and
8ldhTfiJl 7: 2-7.
digestion of alkali-treated straw by Brahman cattle and
Christopherson, R. J. and Kennedy, P. M. 1983. Effect of
Swamp buffaloes. journal of A#x/ttwnl S&IC~, Cnmbridgc
the thermal environment on digestion in ruminants.
114: 177-186.
Cm7ndim ]ournn/ $R~~ind Sciencr 63: 477-496.
Pearson R. A. and Dijkman, J. T. 1994. Nutritional
Collier, R. J. and Beede, D. K. 1985. Thermal stress as a
implications of work in draught animais. Proceedings of the
factor a s s o c i a t e d w i t h nutrient r e q u i r e m e n t s a n d
Nutrition Society 53: 169-179.
interrelationships. ln Nufrifim qfgrming rfminnf~fs
irf wariif
Pearson, R. A. and Lawrence, P. R. 1992. Intake, digestion,
cliaznf~s (cd. L. R. McDowell), pp. 59-71. Academic Press,
gastrointestinal
transit time and nitrogen balance in
London.
working oxen: studies in Costa Rica and Nepal. Anirml
El-Nouty, F. D. and Hassan, G. A. 1983. Thyroid hormone
Prodncfim 55: 361-370.
status and water metabolism in Hereford cows exposed to
Pearson, R. A. and Smith, D. G. 1993. The effects of work
high ambient temperature and water deprivation. 1r1dinrl
on food intake and ingestive behaviour of draught cattle
/ouvu 0fArliml Scierfcc 53: 807412.
and buffalo given barley straw. At~ivml Producfim 58:
Faverdin, P., Baumont, R. and Ingvartsen, K. L. 1995.
339-346.
Control and prediction of feed intake in ruminants. In
Preston, T. R. and Leng, R. A. 1987. M&chirrg runrirmt
Rmwt d~z~clopn~ts il7 fhr nrrtrition o f lwbizwn ( e d . M .
producfim systems reifll mnilnbk reswrccs irl fhc fropics mrd
Journet, E. Grenet, M.-H. Farce, M. Theriez and C.
wb-tropics. Penambul Books, Armidale, Australia.
D e m a r q u i l l y ) . Proccedings of fh ,fourth interrzntima/
synposium OH the rzufrifion of 1wrbioorw pp. 95-120. INRA
Statistical Analysis Systems Institute. 1985. SAS mers
Editions, Paris.
guide: sfntisfics. Statistical Analysis Systems Institute Inc.,
Cary, NC.
Forbes, J. M. 1995. Vohtnry food intakc nrzd dict sclrctiorz in
Weston, R. H. 1985. Some considerations of voluntary feed
,fnrl?r animnls. CAB International, Wallingford.
consumption and digestion in relation to work. In Drnught
Grovum, W. L. and Williams, V. J. 1973. Rate of passage of
n~rirrlnl poxwfor productim (ed. J. W. Copland). Proceedings of
digesta in sheep. 4. Passage of marker through the
un it~turzntionnl
zuorkshoy, ]ntnes Cook Lhizmity, Tozmsz~illt~,
alimentary tract
a n d t h e b i o l o g i c a l relevance o f
Ausfrnlin, 10-16 ]uly 3985. ACIAR proceeding series no. 10,
rate-constants derived from the changes in concentration of
pp. 78-83. ACIAR, Canberra.
marker in faeces. British @mn/ ofh’utritiorr 30: 313-329.
Zerbini, E., Gemeda, T., Wold, A. G., Nokoe, S. and
Lawrence, P. R. and Pearson, R. A. 1985. Factors affecting
Demissie, D. 1995. Effect of draught work on performance
the measurement of draught force, work output and power
and metabolism of crossbred CO~S. 2. Effect of work on
of oxen. ]ourrml of Agricultural Sciencr, Cnmbric@ 105:
roughage intake, digestion, digesta kinetics and plasma
703-714.
metabolites. Arzimnl Scimce 60: 369-378.
Mathers, J. C., Baber, R. P. and Archibald, R. F. 1989.
Intake, digestion and gastro-intestinal mean retention time
in Asiatic buffaloes and Ayrshire cattle given two
(Rmizvd 29 ]annunry 1996~Acrepted 13 S@mber 1996)