Effects of polyethylene glycol in concentrate or feed blocks on carcass composition and offal weight of Barbarine lambs fed Acacia cyanophylla Lindl. foliage
Effects of polyethylene glycol in concentrate or feed blocks on carcass composition and offal weight of Barbarine lambs fed Acacia cyanophylla Lindl. foliage
Naziha ATTI 1
Hichem BEN SALEM 1
Alessandro PRIOLO 0
0 Università di Catania DACPA Sez di Scienze delle Produzioni Animali , Via Valdisavoia 5, 95123 Catania , Italy
1 INRA-Tunisie, Laboratoire de Productions Animales et Fourragères , rue Hédi Karray, 2049 Ariana , Tunisia
- The influence of concentrate or feed blocks with or without Polyethylene glycol (PEG, molecular weight 4000) on the carcass characteristics and weight of offal components of 25 Barbarine ram lambs offered Acacia cyanophylla Lindl. foliage was studied. The animals were divided into 5 equal groups and housed in individual pens for 74 days. All of the animals received 400 g oat hay and air-dried foliage of acacia ad libitum. Two groups were supplemented with 300 g concentrate with (CPEG) or without (C) 20 g PEG. The other groups had free access to urea-containing feed blocks with (BUPEG) or without (BU) PEG. One other treatment was a PEG-containing feed block without urea (BPEG). PEG was used to preferentially bind A. cyanophylla condensed tannins (CT). At the end of the growth trial, the animals were slaughtered, offal components were weighed, left half carcasses were dissected and carcass tissues were weighed. At slaughter, body weight (BW) was the highest (P < 0.01) in the group receiving concentrate and PEG (35.4 kg). The animals on diets C, BPEG and BUPEG were slaughtered at similar BW (33.4, 31.8 and 32.1 kg, respectively) and those on BU had the lowest BW (27.8 kg). Dressing percentage was not affected by diet treatments. The weights of the head, feet, lungs, heart and abomasum were not affected by the diet. The diet significantly influenced the skin, testes, liver, kidneys and rumen weights. The animals fed concentrate had heavier skin (4485 g) and rumen (812 g) than those fed blocks (3773 and 720 g for the skin and rumen, respectively). The animals receiving BU had the smallest organs. On contrasting treatments plus/minus PEG, it was observed that PEG administration significantly increased the weight of all organs. PEG supply significantly increased (P < 0.01) testis weight (196 vs. 127 g with/without PEG). Due to treatment effects on slaughter BW and hence carcass weight, muscle, bone and fat weights were lower in the BU group compared to those in the other groups. In C, CPEG, BPEG and BUPEG groups, there was no significant difference in body muscle weight. Indeed, the animals fed A. cyanophylla with feed blocks with PEG and without urea (BPEG group) produced the same amount of muscle as those produced with PEG and urea-containing feed blocks or conventional diets (concentrate). The
animals given feed blocks (more protein and less energy than the concentrate) were less fat (20.0%)
than those receiving concentrate (24.7%). The use of acacia foliage and feed blocks without urea but
containing PEG may be a useful solution to produce lean lamb in a more economic manner.
lamb / Acacia cyanophylla Lindl. / tannins / concentrate / feed blocks / polyethylene glycol /
carcass quality / offal weight
Résumé — Incorporation dans le concentré ou les blocs alimentaires de polyéthylène glycol :
effets sur la composition de la carcasse et le poids des abats chez les agneaux de race Barbarine
nourris avec des feuilles d’Acacia cyanophylla Lindl. Les effets de la complémentation ou non de
l’aliment concentré ou des blocs alimentaires (BA) avec du PEG sur les caractéristiques des carcasses
et le poids des abats ont été étudiés sur 25 agneaux de race Barbarine alimentés avec une ration à base
de feuillage d’Acacia cyanophylla Lindl. Les animaux ont été répartis en 5 lots homogènes. Logés en
boxes individuels pendant 74 jours, tous les agneaux ont reçu 400 g de foin d’avoine avec du feuillage
d’acacia à volonté. Deux lots ont été supplémentés avec 300 g de concentré avec (CPEG) ou sans (C)
20 g de PEG. Deux autres lots ont eu libre accès aux blocs alimentaires contenant de l’urée avec
(BUPEG) ou sans (BU) PEG. Le dernier traitement a inclu un supplément sous forme de bloc
alimentaire sans urée mais avec du PEG (BPEG). A la fin de la période d’engraissement, les animaux ont été
abattus, tous les organes pesés, les demi-carcasses disséquées et les différents tissus pesés. À
l’abattage, le poids vif des animaux du lot CPEG a été le plus élevé (35,4 kg), celui des animaux des lots C,
BPEG, et BUPEG similaire (33,4, 31,8 et 32,1 kg, respectivement), et celui des animaux du lot BU le
plus faible (27,8 kg). Le rendement à l’abattage n’a pas été affecté par le régime alimentaire, de même
que les poids de la tête, des pattes, des poumons, du coeur et de la caillette. En revanche, le régime
alimentaire a eu un effet significatif sur le poids de la peau, des testicules, du foie, des reins et du rumen.
De ce fait, le poids de la peau et du rumen des agneaux recevant le concentré (4485 et 812 g) a été
supérieur à celui des agneaux recevant les blocs alimentaires (3773 et 720 g), alors que les organes les
plus légers ont été observés chez les animaux recevant le régime BU. L’effet du PEG, testé par la
méthode des contrastes, a montré que l’administration de PEG augmentait le poids des organes. Ainsi, le
poids des testicules a été significativement (P < 0,01) plus élevé chez les agneaux recevant le PEG que
ceux n’en recevant pas (196 avec PEG vs. 127 g sans PEG). Étant donnés les effets du régime
alimentaire sur le poids vif et par conséquent sur le poids de la carcasse, les poids des tissus musculaire,
adipeux et squelettique ont été les plus faibles dans le lot BU. En revanche, dans les lots C, CPEG, BPEG et
BUPEG, la masse musculaire n’a pas été significativement différente. En conséquence, supplémenter
des animaux ayant une alimentation à base de feuilles d’Acacia cyanophylla avec des blocs
alimentaires sans urée mais contenant du PEG permet de produire une masse musculaire comparable à celle
obtenue avec des blocs alimentaires contenant de l’urée et du PEG ou avec des régimes
conventionnels (concentré). Les animaux supplémentés avec les blocs alimentaires (plus de protéines et moins
d’énergie que le concentré) ont été relativement moins gras (20,0 %) que ceux supplémentés avec le
concentré (24,7 %). L’utilisation de feuilles d’acacia avec des blocs alimentaires sans urée mais
contenant du PEG permettrait de produire des agneaux non gras de façon plus économique.
agneaux / Acacia cyanophylla Lindl. / tannins / concentré / blocs alimentaires / polyéthylène
glycol / qualité des carcasses / abats
In arid and semi-arid regions of the
Mediterranean area, particularly Tunisia, sheep
feeding is based on natural resources, range
land and stubble. The availability of such
resources is uncertain. In good years,
grazing is available during a short period (3
to 4 months) in the spring. Out of this
season, the fattening operation is based on
concentrate feeding. Grazing Barbary lambs
reached slaughter age (6 months) with a
higher weight and less fat than feedlot
lambs fed on hay and concentrate [
Furthermore, in feedlot conditions the food
conversion efficiency is rather low which
increases feed costs.
In order to overcome the problem of food
availability and cost, several shrubs and
agro-industrial by-products are used as
alternative feed resources. Acacia cyanophylla
Lindl. foliage and Opuntia ficus indica
(cactus) are the plant species most established
and their fodder potential is known [
The limiting factor of A. cyanophylla is the
presence of condensed tannins (CT). The
beneficial effect of polyethylene glycol
(PEG) supply on the nutritive value of
CTrich feeds has been reported in numerous
papers [e.g. 15, 31, 34]. In a recent work,
Ben Salem et al.  concluded that feed
blocks, a solidified mixture of several
agroindustrial by-products, were a good carrier
of PEG to sheep fed A. cyanophylla. This
means of administering PEG improved the
nutritive value of A. cyanophylla and sheep
growth. Studies on the effect of CT and
their deactivation by PEG on intake,
digestion and growth of ruminants are abundant,
but information about the effects of these
secondary components on the carcass
quality of sheep is lacking. The objective of this
work was to study lamb production on
A. cyanophylla foliage supplemented by
concentrate or feed-blocks with or without
PEG in order to reduce (i) lamb production
cost, feed blocks being less expensive than
concentrate, and (ii) carcass adiposity via
diet quality. Digestive aspects of diets and
sheep growth have been reported
]. This paper investigates the
effects of these regimens on the carcass
composition and offal weight of fat-tail
2. MATERIALS AND METHODS
2.1. Animals and feeding
Twenty-five male Barbarine lambs aged
5 months were separated into 5 groups that
were matched as closely as possible for live
weight (29 (s.d. 2.6) kg) and housed in
individual pens. Before the commencement of
the experiment all of the animals were treated
against internal and external parasites with
Ivomec (MSD-AGVET®). The animals had
free access to water, they received 400 g oat
hay (6.7 MJ of metabolisable energy (ME)
and 74 g crude protein (CP)·kg–1 DM),
airdried foliage of A. cyanophylla ad libitum
(5.6 MJ ME and 153 g CP·kg DM–1) and
supplement. In two groups, the supplement
was 300 g concentrate (10.5 MJ ME and
116 g CP·kg–1 DM), only concentrate in one
(C) and concentrate plus 20 g PEG in the
other (CPEG). In the 3 others, supplements
were feed blocks, which varied with group.
Feed blocks contained urea without PEG
(BU: 6.1 MJ ME and 235 g CP·kg–1 DM), in
the first group and, PEG without urea in the
second (BPEG: 4.2 MJ ME and 101 g CP·kg–1
DM). In the third group, feed blocks
contained both urea and PEG (BUPEG: 5.3 MJ
ME and 253 g CP·kg–1 DM). The animals
were on trial for 74 days during which time
the average daily DM intake of A. cyanophylla
foliage varied between 300 and 500 g. At the
end of the trial, the lambs were slaughtered.
2.2. Measurements at slaughter
Before slaughter, lamb body weights
(BW) were recorded. After slaughter,
omental and mesenteric fat (OMF) were
removed, the weights of the different
components of offal were determined: skin, head,
feet, thoracic organs (heart, lungs +
trachea) and viscera (digestive tract, spleen,
liver and kidney). All fractions of the
digestive tract (reticulo-rumen + omasum
(rumen), abomasum, and intestine) were
weighed full then empty after hand rinsing,
in order to determine the weight of the
Conformation and fat scores of the
carcass were visually determined according to
photographic standards using a 15 point
]. The second parameter was based
on backfat thickness and fat distribution.
Fat colour (white, yellowish or yellow) and
persistence (hard, tender or oily) and lean
colour (red or rosy) were assessed visually.
Warm carcass weight (WCW) was
recorded and then the carcasses were stored at
2.3. Carcass cutting and dissection
The cold carcass weight (CCW) was
recorded 24 h post-mortem after storage at
4 oC. The fat tail was removed and weighed
then the carcass was split longitudinally
into two and the halves were weighed. The
left half-carcass was cut into six joints (leg,
lumbar region, flank, thoracic region, neck
and shoulder) following the procedures of
Colomer et al. [
]. Every joint was weighed
and dissected. The first operation in the
dissection process was the removal of
subcutaneous fat. The muscles were then removed
singly from the bones, finally
inter-muscular fat was trimmed from the muscles and
bones. Other tissues such as tendons, lymph
nodes etc. were separated as waste. Pelvic
fat was removed from the leg and kidney fat
from the thoracic region.
2.4. Calculation and statistical analysis
Empty body weight (EBW) was
calculated as the difference between BW before
slaughter and the weight of digestive
contents. Commercial and real dressing
percentage (CDP, RDP) were calculated
according to the following equations:
CDP (%) = 100 × WCW / BW
RDP (%) = 100 × CCW / EBW.
For each joint, the tissues were weighed
individually; the sum of the weights of each
tissue in all joints represents the weight of
the tissue in the half carcass and was used
for calculation of carcass composition. The
carcass composition data were reported as
percentages. The total tissue weight
recovered after dissection was used as the divisor
in the calculation of percentages of each
tissue. Fat depots were presented as
proportions of total carcass fat (TCF) as real
values, and as carcass fat without fat tail
(CFWFT) to facilitate comparison with
results relative to thin tail breeds.
Statistical analysis was performed by
analysis of variance using the GLM
procedure of SAS [
]. The effects of dietary
treatment on offal component weights,
tissue weights, their proportions in EBW or in
carcass, the different fat depot weights and
their proportions in TCF were analysed
according to the following model:
Yij = µ + Di + eij
(Yij = jth measure of the ith diet; µ = overall
mean; Di = effect of the ith diet (C, CPEG,
BU, BPEG, BUPEG); eij = error term).
Differences between groups were evaluated by the
Duncan t-test; significance was declared at
P < 0.05.
The following contrasts were used to
compare the effects of the different diets:
– (C+CPEG) vs. (BU+BUPEG): combined the
effect of the method of supplementation
and energy/protein supply from the
– (C+BU) vs. (CPEG+BUPEG): global effect
of inclusion of PEG.
– BUPEG vs. BPEG: effect of including urea
– BUPEG vs. BU: effect of inclusion of
PEG in blocks.
– CPEG vs. C: effect of inclusion of PEG in
3.1. Empty body weight, carcass characteristics and dressing percentage
BW at slaughter was affected by diet
(P < 0.05). Almost all the contrasts, except
[BUPEG vs. BPEG] and [CPEG vs. C] were
significant. Indeed, BW was higher in
groups receiving concentrate (34.4 kg) than
in those receiving feed blocks (30.5 kg).
Administering PEG in concentrate had no
effect on BW, however, its incorporation in
feed blocks improved BW (Tab. I). Animals
given PEG-containing feed blocks (BPEG
and BUPEG) were slaughtered at similar
BW (31.8, and 32.1 kg, respectively) which
was significantly higher than that of
animals on the BU-diet (27.8 kg). This effect
of the diet on BW was carried through to
EBW and carcass weight (Tab. I). Dressing
percentage was not significantly affected
by the diet treatments, the mean CDP was
43.8% and the mean RDP was 53.2%.
Carcass conformation score was
significantly affected (P < 0.001) by diet (Tab. I).
and was higher in groups receiving
concentrate (8.1) than in those receiving feed blocks
(5.1). The contrast [C+CPEG vs. BU+BUPEG]
was significant (P < 0.001). The contrast
[BUPEG vs. BU] was highly significant (P <
0.01) but the contrast [CPEG vs. C] was not.
In fact, administering PEG in feed blocks led
to the largest improvement in carcass
conformation score compared to PEG included
in the concentrate. The BU-group had the
lowest score conformation. The carcass fat
score was affected (P < 0.05) by the diet
treatment and contrasts [C+CPEG vs.
BU+BUPEG] and [BUPEG vs. BU] were
significant. The fat score was the highest in
CPEG (Tab. I). Fat consistency and lean
colour were not affected by the treatments. In
all carcasses, the fat was tender and the
lean rose. Fat colour was not the same in
all groups; sheep receiving concentrate had
more carcasses with white than yellowish fat
whereas in sheep fed feed blocks the reverse
3.2. Offal weights
Weights of head, feet, lungs, heart and
intestines were not affected by diet and all
contrasts were not significant except for the
presence of the PEG effect on intestine
weight (Tab. II). Diet effect was significant
for skin, testes, liver, kidneys, rumen and
abomasum weights (Tab. II). Animals
receiving BU had the smallest organs
(Tab. II). The effect of PEG inclusion
[C+BU vs. CPEG+BUPEG] was significant
for all these organs increasing with PEG
administration (Tab. II). The increase of skin,
kidney and rumen weight due to PEG
administration was particularly pronounced
when this reagent was introduced in feed
blocks. Animals fed concentrate had heavier
skin and rumen than those fed blocks; the
[C+ CPEG vs. BU+BUPEG] contrast was
significant (Tab. II). The weight of the digestive
tract contents was higher in the animals
offered concentrate (6957 g) than in those
given feed blocks (6428 g). The animals fed
concentrate had more (P < 0.05) OMF than
those offered feed blocks. The animals
offered blocks had greater proportions of
intestines (P < 0.01) and liver (P < 0.05) in
EBW than those on the concentrate diet
(4.73 and 1.66% vs. 4.21 and 1.53%
respectively). Proportions of head and feet were
affected (P < 0.01) by diet; these organs
were higher with feed blocks than with
concentrate and in animals receiving PEG than
in other groups. Otherwise, sheep given
PEG had the greatest testis proportion
(P < 0.01) in EBW (0.74 vs. 0.52%). OMF
proportion in EBW was the lowest in the
3.3. Carcass composition
3.3.1. Carcass joints
Weights of the leg, shoulder, thoracic
and lumbar regions and fat-tail were
significantly affected by diet (P < 0.01) and were
higher in sheep receiving concentrate
compared to those receiving feed blocks.
Administering PEG led to increasing the
weight of these organs, except for the
fattail which decreased with PEG. As
proportions of the carcass, joints had similar
values on all diets (36, 18.5, 19, 10 and 10 for
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leg, shoulder, thoracic and lumbar regions
and the flank, respectively). They were not
affected by the diet treatment and all
contrasts were not significant, except for the
contrast [C+CPEG vs. BU+BUPEG], which
was significant for the fat-tail proportion
(P < 0.05). Animals fed on concentrate had
relatively bigger tails (7.5%) than those
consuming feed blocks (5.7%).
3.3.2. Carcass tissues
Muscle and adipose tissue mean weights
were significantly affected by the diet
(P < 0.01). However bone weight was not
affected by dietary treatments and [C+CPEG
vs. BU+BUPEG] and [C+BU vs. CPEG+
BUPEG] contrasts were significant. Adipose
tissue weight was bigger in the animals
receiving concentrate than in those receiving
feed blocks. Administration of PEG in the
concentrate resulted in a little increase in
muscle and fat weight, but PEG added to
feed blocks led to an important (P < 0.01)
increase in muscle, fat and bone weight
(Tab. III). The proportion of the carcass muscle
was similar for all diets (53.4%). Inversely, the
proportions of fat and bone were affected
by diet. Sheep given feed blocks were less fatty
(P < 0.01; 20.0%) and had relatively more
bone than those receiving concentrate (24.7%).
The [C+CPEG vs. BU+ BUPEG] contrast was
significant (P < 0.01). Sheep given
concentrate were fatter; hence they had relatively
more subcutaneous and less inter-muscular
and pelvic fat than those fed feed blocks.
Only the tail fat proportion was decreased by
PEG supply. The proportion of kidney fat was
not affected by the treatment (Tab. IV).
Differences in performances observed
between animals receiving concentrate and
those receiving feed blocks are associated
with the method of supplementation
combined to the energy/protein ratio from the
supplement. In fact, the two concentrate
treatments had the same energy and protein
content. However, the three block
treatments differed in protein content and had
similar energy content (5.4 MJ·kg–1) which
was less than the concentrate (10 MJ·kg–1).
Hence the concentrate diet resulted in the
heaviest lambs. Thus, the animals receiving
these diets had the highest EBW and
carcass weight. Introducing PEG in the
concentrate also tended to slightly increase
these traits. Adding PEG to urea feed
blocks (BUPEG) led to an increase of DM
intake and feeding value of the diet [
which resulted in an increase in BW, EBW
and carcass weight with reference to the BU
treatment which had the same energy and
protein content. A similar tendency occurred
with the BPEG treatment, despite the fact that
it contained less protein (101 g CP·kg–1) than
the BU treatment (235 g CP·kg–1), it
permitted a higher BW, EBW and carcass weight.
PEG operated as a precipitating reagent to
deactivate A. cyanophylla CT and hence to
promote increased N availability to rumen
micro-organisms and to the host animal.
However, the BU lambs had the lowest EBW
and carcass weight.
CPEG animals had the best conformation
score. This result may be related to the
highest fat score, since it is difficult to
discriminate between these parameters [
The increase in these parameters resulted
from a BW increase. Numerous authors [
14, 18, 29, 30, 36
] reported such a
Rumen weight was higher for sheep
receiving concentrate with or without PEG
and the PEG-containing feed block. This
trend is associated with the feed intake level
7, 17, 20, 26
], which was more elevated in
C, CPEG, BPEG and BUPEG groups .
Hence the digestive tract content, which is
related to food intake, was heavier in those
groups. On the contrary, these animals were
heavier than BU animals. It is well
established that, in young animals, some parts
of the alimentary tract and particularly the
rumen continue to develop as the animals
become older and heavier [
17, 20, 25, 33
However, the weight of some other organs
increased or tended to increase only by
PEG supplementation (abomasum,
intestines, liver and kidneys). Nutrients
produced by fermentation of PEG-containing
diets are probably important factors in
changes in liver weight . This
phenomenon may explain the higher weight of the
liver and other organs in sheep given PEG
as compared to those fed control diets (i.e.
The weight of offal components high in
bone content and/or with a low metabolic
activity (head, feet and lungs) varied slightly
with diet. Since these components are early
maturing parts [
]; they are less
affected by the dietary effects in growing
The weight of most offal components
was not different between groups
slaughtered at a similar BW, despite the difference
in feed level and quality. This suggests that
the weight of most offal components
depend more on weight at slaughter rather
than on the intake level or diet composition.
It is worth noting that PEG supply
increased the testis weight. It is well
documented that testis weight is correlated to
spermatozoa production [
Therefore, it would be interesting to confirm
these findings on animals given PEG in
CTrich feeds or in other feeds.
Due to the treatment effects on slaughter
BW and hence carcass weight, body muscle,
bone and fat weights were lower in the BU
group compared to those in the other groups.
In C, CPEG, BPEG and BUPEG groups, there
was no significant difference in body muscle
weight. So for animals fed A. cyanophylla,
supplementation by concentrate or feed
blocks with PEG resulted in the same muscle
quantity, whereas PEG added to concentrate
did not act on the muscle quantity, but
administered in feed blocks, this reagent increased
muscle growth. Furthermore, including PEG
in feed blocks without urea (BPEG group) in
animals fed A. cyanophylla led to the same
amount and proportion of muscle as in those
given A. cyanophylla and concentrate or feed
blocks with urea. Indeed, supplementing
animals fed A. cyanophylla with feed blocks
with PEG and without urea (low in CP, BPEG
group) may have deactivated tannins; thus
releasing proteins from protein-tannin
complexes and enhancing protein synthesis. This
quantity of protein seems to be sufficient to
produce the same amount of muscle as that
produced with PEG and urea-containing feed
blocks or conventional diets (concentrate).
Body fat increased in weight (and
proportions) in concentrate groups compared
to feed block groups. Energy and protein
] of diets containing
concentrate (10 MJ and 116 g CP·kg–1 DM) or feed
blocks (6 MJ and 101 or 235 g CP·kg–1 DM)
partly explain the difference in body fat
contents. Indeed, both PEG-containing
feed block diets having the high ratio of
protein to energy led to the same muscle
weight and proportion but less fat than
concentrate diets. Sheep given concentrate had
relatively more subcutaneous and less
inter-muscular fat. The subcutaneous fat
deposition occurs late, hence its proportion
increased when total body fat increased
while for inter-muscular fat, an early
maturing depot, the inverse occurred. This order
of deposition has been confirmed in several
2, 3, 6, 8, 23
Referring to earlier studies on Barbarine
lambs slaughtered at the same weight and
age, animals used in the current experiment
(fed A. cyanophylla) and supplemented with
concentrate were less fatty (24.7%) than
those kept in the feedlot and given oat-vetch
hay ad libitum and concentrate (29.7%; [
This trend was expected since animals used
in the current experiment were offered diets
having a high ratio of protein to energy.
However, the conventional fattening
regimen is more expensive, needing more hay
(0.6 to 1 kg DM·lamb–1·day–1) and more
concentrate (0.6 kg·day–1). On the contrary,
animals fed A. cyanophylla and
supplemented with feed blocks were less fatty than
those used in the previous work, and they
have a fat level (20%) similar to lambs fed at
pasture (20%, [
]). Hence, it may be
possible to produce lean lambs without a problem
of food availability, using A. cyanophylla
foliage and feed blocks with PEG.
Using PEG-containing feed blocks as a
supplement to animals fed A. cyanophylla,
resulted in the same amount of muscle as
that produced by lambs given concentrate
as a supplement to A. cyanophylla.
Furthermore and in conjunction with differences in
energy content and protein to energy ratio,
diets supplemented with PEG-containing
feed blocks decreased carcass fatness by
40 g·kg–1 of side carcass. For animals fed
A. cyanophylla, the use of feed blocks with
PEG and without urea, may permit savings
on urea use since it produced carcasses of
similar composition to that produced by a
regimen supplemented with feed blocks
containing both PEG and urea.
Barbarine lambs given A. cyanophylla
and concentrate or feed blocks with PEG
had reduced carcass fatness compared to those
fed a common diet (oat hay and
concentrate). So finishing lambs on A. cyanophylla
supplemented with either concentrate or
feed blocks containing PEG produced less
fat and hence were more economically
efficient and addressed partially the problem of
food availability. The use of feed blocks
without urea but containing PEG for sheep
fed acacia foliage may be of benefit to
producers seeking to produce lean carcasses in
a more economic manner.
The authors are indebted to N. Amari, J.
Khlil and T. M’Zougui for technical help during
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