Effects of polyethylene glycol in concentrate or feed blocks on carcass composition and offal weight of Barbarine lambs fed Acacia cyanophylla Lindl. foliage

Animal Research, Jul 2018

Naziha Atti, Hichem Ben Salem, Allessandro Priolo

A PDF file should load here. If you do not see its contents the file may be temporarily unavailable at the journal website or you do not have a PDF plug-in installed and enabled in your browser.

Alternatively, you can download the file locally and open with any standalone PDF reader:


Effects of polyethylene glycol in concentrate or feed blocks on carcass composition and offal weight of Barbarine lambs fed Acacia cyanophylla Lindl. foliage

Anim. Res. 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 1. INTRODUCTION 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 [ 4, 5 ]. 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 [ 9, 10 ]. 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. [11] 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 previously [ 12 ]. This paper investigates the effects of these regimens on the carcass composition and offal weight of fat-tail Barbarine sheep. 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 digestive contents. Conformation and fat scores of the carcass were visually determined according to photographic standards using a 15 point scale [ 16 ]. 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 +4 oC. 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. [ 13 ]. 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 [ 32 ]. 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 supplement. – (C+BU) vs. (CPEG+BUPEG): global effect of inclusion of PEG. – BUPEG vs. BPEG: effect of including urea in blocks. – BUPEG vs. BU: effect of inclusion of PEG in blocks. – CPEG vs. C: effect of inclusion of PEG in concentrate. 3. RESULTS 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 occurred. 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 BU group. 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 g G : E U P ;B g n EG iin P ta d n n o a c P * * s s s * s d . C * * n n n * n PEG rgo y ) .s tl 5 v + C d : C , P iln .00 se ten odyb .t t()kg rseco t)(kg rseco tlraeb leepm;eagRD saeemP:*< ean enm ) iehg iton ) iehg iton lltoh sup tecn tinh ;01* M.lIeabttracaeh ()kgW (kgBW rssacaw ()PD% ()PD% fraonom trsaceo ttrssona ()kgW (kgBW rssacaw ()PD% ()PD% franoom trsaceo tisaahnd :rgopu iregnp seanMP.*00< T e B E C C R C F C B E C C R C F In BPEG rssed,,cab: :** BU 6134 656 c3053 a119 120 b365 447 84 86 44 07 09 +B c a 9 b U 6 1 1 3 C h e CPEG 7881 375 a6944 b029 155 445 481 90 48 81 22 32 PE c a a b 1 a G a n 8 1 1 6 U o B + ab a b s C 8137 969 2754 134 138 a973 510 88 767 416 108 508 +C C t h g i e G E ab a 8 ab P Carcass quality of sheep given acacia with or without PEG 369 G E P U B c b b b ab b 1 ab EG BPEG 7617 867 807 194 167 a140 486 97 01 66 15 00 P 8 1 1 5 U 3 .E .3 .1 .4 .S 22 12 113 .86 .45 .82 .158 .52 .431 .94 .228 .013 svG sn sn sn ** sn * sn ** sn * sn sn sn E P G ab b a 6 b .B BUPE 1821 674 206 184 138 422 508 103 cb57 b17 11 41 4 5 9 7 sv sn sn ** sn sn sn sn sn sn sn sn sn 0< G 4 E P M. sum se ts sum se lIeab ead tee ink tisse trae+ irev sgnu+ isendy RO aobm ttisen FM trnoa ead tee ink tisse trae+ irev sgnu+ isendy RO aobm ttisen FM ,cb:eM:RRO I s a e T H F S T H L L K R A In O C H F S T H L L K R A In O ,a R t a f c i d a r e ica ch r a e tr p t a f c i d a r e ica ch r a e tr p .E .3 69 .26 .24 .31 .46 sv * s s s s s n . 6 . G * n n n n n ;5 S 5 0 2 0 7 0 PE .0 0 U B U B . G E P s b m a a l f o B 35 5 1 2 4 U ) 2 1 2 c d b PEG 19 .34 545 ab.1 62 .5 PE b a G 1 b c b U le U 32 .44 724 a.36 307 .91 +B o h B 29 5 1 2 1 1 C e g a t n e c re a a a G p PEG 71 .20 418 c.99 00 .4 PE a 9 5 s C 38 5 1 1 1 2 U a v e G u E ss a c ab ab P tifo C 4643 .524 6146 b.112 6791 .923 +CC W C ( s s a c r a c w f o d n a ) g ( s t h g i e w n a e n i M. )g W W W s )g W W W s I ( C ) C C ts ( C ) C C an lIIeabT lsecuM % (egnoB % t)(agF % tranoC lsecuM % (egnoB % t)(agF % ,,cab:eM < CP ** sn sn sn * sn P( U sB *** sn * *** *** ** t . n e r e f f i d t C n a c i f i n n o ig s U s bm .B ton lfa ..SE .613 .051 .710 .121 .308 .208 .26 .022 .024 .614 .043 .091 .499 .087 svG sn sn sn sn sn sn sn sn sn sn sn sn sn * :sn o E P CarcassqualityofsheepgivenacaciawithorwithoutPEG 371 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). 4. DISCUSSION 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 [ 12 ] 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 [ 22 ]. The increase in these parameters resulted from a BW increase. Numerous authors [ 1, 14, 18, 29, 30, 36 ] reported such a relationship. 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 [12]. 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 [27]. 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. without PEG). 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 [ 28, 35 ]; they are less affected by the dietary effects in growing animals [21]. 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 [ 19, 24 ]. 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 contents [ 12 ] 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 breeds [ 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%; [ 5 ]). 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%, [ 5 ]). Hence, it may be possible to produce lean lambs without a problem of food availability, using A. cyanophylla foliage and feed blocks with PEG. 5. CONCLUSIONS 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. ACKNOWLEDGMENTS The authors are indebted to N. Amari, J. Khlil and T. M’Zougui for technical help during this work. [1] Atti N. , Khaldi G. , Étude comparative de la qualité des carcasses d'agneaux de races Barbarine et Noire de Thibar en fonction du poids d'abattage , Ann. INRAT 60 ( 1987 ) 20 . [2] Atti N. , Khaldi G. , Composition de la carcasse et qualité de la viande d'agneaux de races Barbarine et Noire de Thibar en fonction du poids d'abattage , Ann. INRAT 61 ( 1988 ) 24 . [3] Atti N. , Khaldi G. , Caractéristiques de croissance chez des agneaux de trois races Tunisiennes, in: Symposium “philoetios” sur l'évaluation des ovins et des caprins Méditerranéens, rapport Agrimed EUR 11893 FR- EN, 1989 , pp. 375 - 381 . [4] Atti N. , Abdouli H. , Effets du niveau alimentaire et de la race sur la croissance et la qualité de carcasses des agneaux, Opt . Méd. Série A ( 1997 ) 195 - 198 . [5] Atti N. , Abdouli H. , Effets du niveau du concentré sur les performances bouchères des agneaux de race Barbarine conduits au pâturage ou en bergerie , Ann. INRAT 73 ( 2000 ) 151 - 163 . [6] Atti N. , Bocquier F. , Adaptation des brebis Barbarine à l'alternance sous-nutritionréalimentation : effets sur les tissus adipeux , Ann. Zootech. 48 ( 1999 ) 189 - 198 . [7] Atti N. , Nozière P. , Doreau M. , Kayouli C. , Bocquier F. , Effects of underfeeding and refeeding on offal weight in the Barbary ewes , Small Ruminant Res . 38 ( 2000 ) 37 - 43 . [8] Benevent M. , Croissance relative pondérale postnatale, dans les deux sexes, des principaux tissus et organes de l'agneau Mérinos d'Arles, Ann. Biol. Biochem. Biophys . 11 ( 1971 ) 5 - 39 . [9] Ben Salem H. , Nefzaoui A. , Abdouli H. , Ørskov E.R. , Effect of increasing level of spineless cactus (Opuntia ficus indica var. inermis) on intake and digestion by sheep fed straw-based diets , Anim. Sci . 62 ( 1996 ) 293 - 299 . [10] Ben Salem H. , Effets de l' Acacia cyanophylla Lindl. sur l'ingestion et la digestion des régimes destinés aux ovins. Rôle des tanins et perspective d'amélioration de sa valeur alimentaire , Thèse Doctorat de l'Université de Dijon, France, 1998 , 252 p. [11] Ben Salem H. , Nefzaoui A. , Ben Salem L., Tisserand J.L. , Deactivation of condensed tannins in Acacia cyanophylla Lindl. foliage by polyethylene glycol in feed blocks. Effect on feed intake, diet digestibility, nitrogen balance, microbial synthesis and growth by sheep , Livest. Prod. Sci . 64 ( 2000 ) 51 - 60 . [12] Ben Salem H. , Atti N. , Priolo A. , Nefzaoui A. , Polyethylene glycol in concentrate or feed blocks to deactivate condensed tannins in Acacia cyanophylla Lindl . foliage. 1. Effects on intake, digestion and growth by Barbarine lambs , Anim. Sci . 75 ( 2002 ) 127 - 135 . [13] Colomer-Rocher F. , Dumont B.L. , Murillo F.N.L. , Desccripcion del despiece ovino aragones y definicion de un despiece de referencia normalizado , Ann. INIA Ser. Prod. Anim . 3 ( 1972 ) 79 - 108 . [14] Colomer-Rocher F. , Espejo D.M. , Influence du poids d'abattage et du sexe sur les performances de boucherie des agneaux issus du croisement Manchego × Rasa Aragonesa , Ann. Zootech. 21 ( 1972 ) 401 - 414 . [15] Degen A.A. , Mishorr T. , Makkar H.P.S. , Kam M. , Benjamin R.W. , Becker K. , Schwartz H.J. , Effect of Acacia saligna with and without administration of polyethylene glycol on dietary intake in desert sheep , Anim. Sci . 67 ( 1998 ) 491 - 498 . [16] Delfa R. , Clasificación de canales ovinas en la C.E.E., el quinto cuarto, Edit., Diputación General de Aragón, Serie Estudios Agrarios , 1992 , 117 p. [17] Drouillard J.S. , Klopfenstein T.J. , Britton R.A. , Bauer M.L. , Gramlich S.M. , Wester T.J. , Ferrell C.L. , Growth, body composition, and visceral organ mass and metabolism in lambs during and after metabolizable protein or net energy restrictions , J. Anim. Sci . 69 ( 1991 ) 3357 - 3375 . [18] Flamant J.C. , Boccard D. , Estimation de la qualité de la carcasse des agneaux de boucherie, Ann. Zootech. 15 ( 1966 ) 89 - 113 . [19] Foote R.H. , Factors influencing the quantity and quality of semen harvested from bulls, rams, boars and stallions , J. Anim. Sci . 47 ( Suppl . 2) ( 1978 ) 1 . [20] Kabbali A. , Johnson D.W. , Goodrich R.D. , Allen C.E. , Effects of undernutrition and refeeding on weights of body parts and chemical components of growing Moroccan lambs , J. Anim. Sci . 70 ( 1992 ) 2859 - 2865 . [21] Kamalzadeh A. , Koops W.J., van Bruchem J. , Tamminga S. , Zwart D. , Feed quality restriction and compensatory growth in growing sheep: development of body organs , Small Ruminant Res . 29 ( 1998 ) 71 - 82 . [22] Kempster A.J. , Cuthbertson A. , Harrington G. , The relationship between conformation and the yield and distribution of lean meat in the carcass of British pigs, cattle and sheep , Meat Sci. 6 ( 1982 ) 37 - 53 . [23] Little D.A. , Sandland R.L. , Studies on the distribution of body fat in sheep during continuous growth, and following nutritionnal restriction and rehabilitation , Aust. J. Agric. Res . 26 ( 1975 ) 363 - 374 . [24] Mahouachi M. , Variations saisonnières de la production spermatique chez les béliers de races Barbarine et Noire de Thibar, Mémoire de Spécialisation de l' I.N.A.T. , 1985 , 140 p. [25] Murray D.M. , Tulloh N.M. , Winter W.H. , The effect of three different growth rates on some offal components of cattle , J. Agric. Sci . (Camb.) 89 ( 1977 ) 119 - 128 . [26] Nozière P. , Attaix D. , Bocquier F. , Doreau M., Effects of underfeeding on weight and cellularity of splanchnic organs in ewes , J. Anim. Sci . 77 ( 1999 ) 2279 - 2290 . [27] Ortigues I. , Doreau M. , Responses of splanchnic tissues of ruminants to changes in intake: absorption of digestion end products, tissue mass, metabolic activity and implications to whole animal energy metabolism , Ann. Zootech. 44 ( 1995 ) 321 - 346 . [28] Prud'hon M. , La croissance globale de l' agneau : ses caractéristiques et ses lois , in: Deuxième Journées de la Recherche Ovine et Caprine : Croissance, engraissement et qualité des carcasses d'agneaux et de chevreaux , INRAITOVIC , 1976 , pp. 6 - 20 . [29] Sañudo A.C. , Sierra Y. , Correlaciones entre diversos caracters productivos en el ternasco Aragones , in: IV Jornadas scientificas de Sociedad Espanola de Ovinotecnica, 7 - 9 June 1979. [30] Sents A.E. , Walters L.E. , Whiterman J.V. , Performance and carcass characteristics of ram lambs slaughtered at different weights , J. Anim. Sci . 55 ( 1982 ) 1360 - 1369 . [31] Silanikove N. , Nitsan Z. , Perevolotsky A. , Effect of a daily supplementation of polyethylene glycol on intake and digestion of tannin-containing leaves (Ceratonia siliqua) by sheep , J. Agric. Food Chem . 42 ( 1996 ) 2844 - 2847 . [32] Statistical Analysis Systems Institute, SAS User's Guide: Statistics (6th ed.), Statistical Analysis Systems Inc ., Cary, NC , 1988 . [33] Thériez M. , Touraine B. , Vigneron P. , Prud'hon M., Effects of indoor or outdoor rearing on the chemical composition of lambs, Anim . Prod. 54 ( 1992 ) 389 - 393 . [34] Waghorn G.C. , Reed J.D. , Ndlovu L.R. , Condensed tannins and herbivore nutrition , in: Buchanan-Smith J.G. , Bailey L.D. , Mc Caughy P . (Eds.), Proceedings of the 18th International Grassland Congress , Association Management Centre, Calgary, AB, 1999 , pp. 153 - 166 . [35] Wallace L.R. , The growth of lamb before and after birth in relation to the level of nutrition , J. Agric. Sci . 39 ( 1948 ) 93 - 103 . [36] Wood J.D. , Mc Fie H.J.H. , The significance of breed in the prediction of lamb carcass composition from fat thickness measurements , Anim. Prod . 31 ( 1980 ) 315 - 319 .

This is a preview of a remote PDF: http://animres.edpsciences.org/articles/animres/pdf/2003/04/Z3408.pdf

Naziha Atti, Hichem Ben Salem, Allessandro Priolo. Effects of polyethylene glycol in concentrate or feed blocks on carcass composition and offal weight of Barbarine lambs fed Acacia cyanophylla Lindl. foliage, Animal Research, 363-375, DOI: doi:10.1051/animres:2003022