Growth performance,nutrient digestibility,and slaughter traits of male fattening lambs under different feeding standards

This study compared the growth performance, nutrient utilization, and slaughter traits of Dorper crossbred male lambs fed as per the established nutrition recommendations for sheep, with an aim to verify the efficacy of different feeding standards. A total of 576 lambs (4 months of age, 28.3 ± 0.86 kg BW) were randomly allotted to 3 treatments with 12 replicates per treatment (16 lambs per replicate). The lambs were fed diets formulated according to the following 3 nutritional systems: the nutrient requirements of Dorper crossbred lambs established by Chinese Academy of Agricultural Sciences (CAAS), NRC (National Research Council), (2007), and AFRC (Agricultural and Food Research Council) (1993). The experiment lasted for 81 d. Feed intake was recorded every 3 days, and lambs were weighed every 20 days. Digestibility trials were conducted with 6 lambs each group from d 42 to 53 and d 70 to 81. At the end of the experiment, 10 lambs randomly chosen from each group were sacrificed to determine the carcass traits and meat quality. The results indicated that the lambs in the NRC group had the highest dry matter intake (DMI), followed by those in the AFRC and CAAS groups (P < 0.05). The average daily gain, carcass weight, and dressing percentage were higher for lambs in the CAAS group than those in the NRC group (P < 0.05). The lambs in the CAAS group had the lowest feed conversion ratio, followed by those in the AFRC and NRC groups (P < 0.05). The apparent digestibility of DM was higher for the lambs in the CAAS group than those in the NRC group (P < 0.05). Water losing rate, as well as the lightness (L*), redness (a*), and yellowness (b*) values of the longissimus thoracis were not different among groups (P > 0.05). In conclusion, Dorper crossbred lambs fed diets formulated according to the CAAS recommendations exhibited superior growth performance than those fed diets formulated according to the American or British feeding standards.     

Effects of increasing amount of dietary Prosopis laevigata pods on performance,meat quality and fatty acid profile in growing lambs

A study with finishing lambs assessed the effect of dietary inclusion of Prosopis laevigata pods (PLPs) on performance, carcass characteristics, meat traits and fatty acid profile of subcutaneous fat. Twenty‐one Rambouillet lambs (27.0 ± 3.0 kg BW) were assigned to one of three experimental diets with 0, 150 and 300 g PLP/kg DM. Evaluation of growth performance lasted 49 days. The experimental design was completely randomized and analysed with a mixed model. Lambs fed diets with 0, 150 and 300 g PLP had similar growth performance. Lambs fed diets with 300 g PLP/kg DM had better (p < 0.05) carcass yield and classification, less (p < 0.05) fat deposition and lower lightness (L*) value (p < 0.05) in meat than lambs fed diets with 0 and 150 g PLP/kg DM. Saturated fatty acids (palmitic and stearic) decreased (p < 0.05) and unsaturated fatty acids (oleic and linoleic) increased (p < 0.05) in subcutaneous fat of lambs fed diets with 150 and 300 g pods as compared with lambs not fed PLP. Prosopis laevigata pods are a safe feedstuff that can replace a third of conventional ingredients and reduce feed costs in growing lambs. Addition of PLP reduced (p < 0.05) total feed cost by 21%.     

The effects of replacing <Emphasis Type="Italic">Dichantium</Emphasis> hay with banana (<Emphasis Type="Italic">Musa paradisiaca)</Emphasis> leaves and pseudo-stem on carcass traits of Ovin Martinik sheep

A study was done to evaluate banana (Musa paradisiaca) as a forage (leaves and pseudo-stems) for feeding Ovin Martinik lambs (OMK), with the aim to test its impact on carcass quality. Forty four intact OMK male were used after weaning with an initial mean live weight of 14.4 (± 3.3) kg, reared in individual pens. Animals were offered either Dichantium hay (control diet, Dh) or cut chopped leaves and pseudo-stems of banana (experimental diet, Blps). They were fed 200—250 g.d⁻¹ of commercial concentrate. Lambs were slaughtered according to 3 classes of slaughter weight (SW): SW20, SW23 and SW26. Growth and carcass performances of both groups were not significantly different, 77 vs. 81 g.d⁻¹ and 42% vs. 43% hot carcass yield, for Dh vs. Blps, respectively. There was a significant (P < 0.05) decrease (31.0 vs. 29.7%) for the dry matter content of the shoulder for lambs fed the banana diet. However, there was no effect observed for the other chemical component (CP, lipid and mineral 585, 317 and 95 g.kg⁻¹DM, respectively). The shoulder (20% of the carcass whatever the SW) was precocious as demonstrated by the allometry coefficient relative to carcass weight (0.894) significantly (P < 0.01) less than 1. It was concluded that, the use of Blps had no significant effect on growth, carcass weights and yields of the OMK lambs, irrespective of the class of the slaughter weight. From these initial results, the use of banana foliages and pseudo-stems could be recommended as sources of forages.     

Effects of yeast culture supplementation and the ratio of non‐structural carbohydrate to fat on growth performance,carcass traits and the fatty acid profile of the longissimus dorsi muscle in lambs

The effects of yeast culture (YC) supplementation and the dietary ratio of non‐structural carbohydrate to fat (NSCFR) on growth performance, carcass traits and fatty acid profile of the longissimus dorsi (LD) muscle in lambs were determined in a 2 × 3 full factorial experiment. Thirty‐six Small‐tailed Han lambs were randomly divided into six groups with six replicates per group. The lambs were fed one of the six pelleted total mixed rations (TMRs) for 60 days after 15 adaption days. The six rations were formed by two NSCFRs (11.37 and 4.57) and three YC supplementation levels (0, 0.8 and 2.3 g/kg dietary dry matter). The average daily gain (ADG), dry matter intake (DMI) and feed conversion ratio (FCR) data of each lamb were recorded and calculated. All the lambs were slaughtered for determining carcass traits and fatty acid profile of the LD muscle. DMI was significantly increased (p < 0.05) in a quadratic fashion with 0.8 g/kg of YC supplementation. Carcass weight (CW) and dressing percentage (DP) were significantly increased (p < 0.05) in a linear fashion with 2.3 g/kg of YC supplementation. Animals fed with high‐NSCFR diet had higher (p < 0.05) contents of myristoleic acid (C14:1), pentadecanoic acid (C15:0) and cis‐10‐heptadecenoic acid (C17:1), and lower (p < 0.05) stearic acid (C18:0) content in LD muscle than those fed with low‐NSCFR diet. Moreover, ADG, growth rate (GR), backfat thickness (BFT), percentages of crude fat (CF) and crude protein (CP), SFAs, MUFAs and PUFAs in LD muscle, were significantly affected (p < 0.05) by interaction of dietary NSCFR and supplemental YC level. Overall, YC not only improved the growth performance and carcass traits of the animals but also modified the fatty acid profile of the LD muscle. Furthermore, the effects of YC supplementation may depend on dietary compositions.     

The effects of diet,slaughter weight and docking on growth,carcass composition and meat quality of fat-tailed Barbarine lambs. A review

This review summarises the main factors that influence meat production and quality in fat-tailed Barbarine (FTB) lambs. As a general feature, FTB lamb's growth is moderate, and the average daily gain ranges between 100 and 350 g. The carcass being relatively fatty, carcass fat content varies from 10% to 32%; white fat and rose meat are often dominant in these carcasses. The meat fatty acid profile of this fat-tailed breed is similar to that of thin-tailed ones, with a prevalence of palmitic, stearic and oleic acids. The order of dissected adipose tissues accumulation, estimated by allometry coefficients, is in agreement with observations in thin-tailed sheep. However, tail fat allometry coefficient is closer to kidney fat values rather than to the subcutaneous one. Concerning effects of feed level, growth of FTB lambs fed silage is higher than those fed oat hay. With moderate concentrate supply, FTB lambs' growth is more pronounced on pasture diet than on the feedlot (FL) diet. Furthermore, at similar slaughter weights, carcasses of lambs fed pasture diet have less tail and carcass fat than those from lambs fed FL diet (5% and 18% vs. 9% and 24% for grazing and FL lambs, respectively). No difference in fat colour, fat firmness or cooked meat flavour is observed between carcasses obtained at different slaughtering weight (i.e. from 25 to 35 kg). The tail docking of FTB improved lambs' growth particularly before weaning. Its effect on carcass composition and fat proportion depends on stage of slaughtering and type of fattening diet. For suckled lambs (4 months), the docking resulted in the lower carcass fat weight (and proportion), while for fattened lambs, carcass composition was similar for all types of lambs. Overall, FTB lambs always grow slower than Noire de Thibar lambs. This is particularly pronounced during the fattening phase. Then, for FTB breed, the possibilities to obtain heavy carcasses are at risks of fat accumulation, 22.8% vs. 14.4% for FTB and Noire de Thibar thin-tailed lambs, respectively. However, the main advantage of FTB breed is that adults are well adapted to food scarcity and may produce lambs even under harsh conditions.     

Relationship between the activity of mitochondrial respiratory chain complexes and feed efficiency in fat-tailed Ghezel lambs

This study was conducted to investigate relationships between mitochondrial respiratory chain complex activities, feed efficiency, and carcass traits in sheep. A group of Ghezel male lambs sired by a single ram were randomly allotted to individual pens. The lambs were fed ad libitum with a fattening diet containing 30% roughage (corn silage and alfalfa hay) and 70% concentrate for 70 d to individually phenotype each lamb for feed conversion ratio (FCR), adjusted FCR (aFCR), and residual feed intake (RFI). The lambs were then humanely killed and the liver, abdominal fat, pelvic fat, cardiac fat, warm carcass weight, and cold carcass weight, as well as the cross-sectional area of the LM and the fat depth over the 12th rib, were determined. A portion of LM was obtained to determine mitochondrial protein and respiratory chain complex activities (complexes I to V). Statistical analysis was carried out based on lambs exhibiting high and low RFI (n = 8), FCR (n = 8), or aFCR (n = 8) phenotypes. The lambs exhibiting the high-RFI phenotype consumed 110 g more feed daily (P < 0.05) than did the phenotype exhibiting low RFI, with no difference in ADG. Conversely, there was no difference in feed intake between the low- or high-FCR groups, but sheep exhibiting the low-FCR phenotype gained 70 g more (P < 0.05) per day compared with those exhibiting the high-FCR phenotype. It was determined that all 5 respiratory chain complex activities were greater (P < 0.05) in sheep exhibiting the low-RFI phenotype compared with those exhibiting the high-RFI phenotype, with significant (P < 0.001) negative correlation coefficients between RFI and respiratory chain complex activity. When efficiency was assessed using FCR, only activities of respiratory chain complexes III, IV, and V were less (P < 0.05) in the low-FCR phenotype compared with the high-FCR phenotype, and there were no differences (P > 0.1) in respiratory chain complex activities between groups when FCR was adjusted for metabolic BW (aFCR). There were no differences (P > 0.1) in carcass traits among any of the feed efficiency phenotypes. The results suggest that the inclusion of respiratory chain complex activities in breeding programs may be helpful in selecting for sheep exhibiting the low-RFI phenotype.     

Effects of cinnamaldehyde, garlic and juniper berry essential oils on rumen fermentation, blood metabolites, growth performance, and carcass characteristics of growing lambs

The objective of this study was to examine the effects of cinnamaldehyde (CDH), garlic (GAR) and juniper berry (JUN) essential oils (200 mg/kg of DM) on performance and carcass characteristics of lambs fed a barley-based concentrate diet ad libitum. For this purpose, 40 ewes' lambs (23.5 ± 1.11 kg initial live weight, LW) were used in a random block design over a 13-week period. Feeding CDH, GAR or JUN did not affect dry matter intake (DMI) but the average daily gain (ADG) of lambs supplemented with CDH and JUN was higher (P = 0.002) as compared to lambs fed GAR or the control diet. Feed conversion (DMI/ADG) was numerically improved when lambs were fed CDH (4.8) and JUN (4.7) compared to those fed GAR (5.2) or the control diet (5.3). There were no effects of feed additives on ruminal pH and concentrations of ammonia and total VFA. Serum concentrations of glycerol and total glycerides were lower and higher (P ≤ 0.03) in lambs fed CDH or JUN respectively, as compared to lambs fed GAR or the control diet. Hot dressed carcass weight was similar among treatments (23.7 ± 0.75 kg; P = 0.18) whereas saleable meat tended (P = 0.13) to increase (+ 9%) in lambs fed CDH and JUN compared to those fed GAR or the control diet. Feeding CDH, GAR or JUN had little effect on the overall fatty acid composition of back fat and liver and only minor effects on meat flavour characteristics.     

Effects of early experience with low‐quality roughage on feed intake,digestibility and metabolism in lambs

The objective of this study was to compare the feed intake, digestibility and metabolism in lambs fed low‐quality roughage with those of lambs fed normal roughage from an early stage of their life. The study consisted of two treatments [low‐quality roughage group (LR) and control group (C)] over three time periods (P1, P2 and P3; 2 months each). Four lambs (4 months old) were allocated to each treatment. In P1 and P2, LR was fed sudangrass hay (CP: 5.1% DM; NDF: 70.4% DM), whereas C was fed timothy hay (CP: 8.4% DM; NDF: 60.3% DM). In P3, all lambs were fed sudangrass hay. Although the feed intake was significantly greater (p < 0.05) in C in P1, there were no differences between the groups in P2. The digestibility, serum glucose (GLU), urea nitrogen (SUN) and insulin‐like growth factor 1 (IGF‐1) did not differ between the groups in P1 and P2. The average nitrogen retention, triiodothyronine (T3) and thyroxine (T4) were significantly higher in C (p < 0.05) during P1 and P2. No interaction was observed between the treatment and periods. In P3, the feed intake was greater in C (p < 0.05), whereas digestibility and nitrogen retention tended to be greater in LR. The body weight did not differ between the treatments. T4 and T3 were numerically lower in LR, while the SUN was greater in LR (p < 0.05). These results suggest that the early experience with low‐quality roughage may have improved feed digestibility and nitrogen metabolism in lambs after 4 months of rearing. Furthermore, the experienced lambs became more efficient at utilizing the low‐quality roughage. The lower thyroid hormone concentrations observed in LR suggest an adaptive change occurred in experienced lambs that to a lower basal metabolic rate.     

Impact of restricting feed and probiotic supplementation on growth performance,mortality and carcass traits of meat‐type quails

The objective of this study was to evaluate the effects of quantitative feed restriction, along with dietary supplementation with a probiotic blend (Protexin) as a natural growth promoter, on the performance, water consumption, mortality rate and carcass traits of meat‐type quails. A total of 250 1‐day unsexed quails were randomly allocated to five equal groups in a completely randomized design. The first group (A) fed a basal diet without any restriction (24 hr/day); the second group (B1) fed the basal diet for 20 hr/day; the third group (B2) fed the basal diet enriched with probiotic (0.1 g/kg diet) for 20 hr/day; the fourth group (C1) fed the basal diet for 16 hr/day; and the fifth group (C2) fed the basal diet enriched with probiotic (0.1 g/kg diet) for 16 hr/day. Birds were fed ad‐libitum from 0–14 days of age, and then the feed restriction regimes started from 14 till 28 days of age. Results showed that quails in the control‐group consumed more feed and water than the other treatment groups (p < .01), however their body weights did not differ (p > .05) compared with the other treated groups. The best feed conversion values were achieved in quails supplemented with probiotic blend (B2 and C2) in comparison with the other groups (p < .01). Feeding probiotic had a positive effect on bird health which reduced the mortality rate. Further, mortality rate was significantly reduced (p < .05) by feed restriction, with or without probiotic supplementation. No carcass parameters were significantly affected (p > .05) by treatments. Our results show that quail could be reared under a feed restriction system, for 4–8 hr daily, along with dietary supplementation of probiotic as growth promoter for better growth performance.     

Effect of a Hydrated Sodium Calcium Aluminosilicate on Growth Performance and Carcass Traits of Pigs

Three experiments were conducted to determine the effect of a hydrated sodium calcium aluminosilicate (HSCA) on growth and carcass traits of finishing pigs. In Experiment 1, 32 barrows (initial weight = 26.7 kg) were fed one of two dietary treatments: 1) a corn-soybean meal basal (B) diet or 2) B + 0.50% HSCA. In Experiments 2 and 3, 64 barrows and gilts were used in a 2 × 2 factorial arrangement of treatments. Two percentages of HSCA (0 or 0.50%) were fed to barrows or gilts. In Experiment 1, average daily gain, feed intake, gain:feed, serum urea nitrogen (SUN) concentration, and carcass traits were not affected (P>0.10) by HSCA. Leaf fat weight was decreased (P<0.08) in pigs fed HSCA. In Experiments 2 and 3, no HSCA × gender interactions (P>0.10) were present; thus, barrow and gilt data were combined. In Experiment 2, average daily gain, feed intake, gain:feed, SUN, and carcass traits were not affected (P>0.10) by HSCA. In Experiment 3, average daily gain, feed intake, and gain:feed were not affected (P>0.10) by HSCA. Serum urea nitrogen was increased (P<0.05) in pigs fed HSCA. Carcass traits were not affected (P>0.10) by HSCA, with the exception of increased (P<0.10) total carcass fat (total body electrical conductivity) in pigs fed HSCA. Pork quality score for color was increased (P<0.09) in pigs fed HSCA, but scores for marbling and firmness-wetness were not affected (P>0.10). In summary, HSCA did not affect growth performance or consistently affect carcass traits.     

全价颗粒饲料与传统精、粗料混合饲喂技术对肉羊育肥效果的对比试验

为了加快内蒙古五原县肉羊产业发展,增加养殖户经济效益,探讨不同饲料对肉羊育肥增重效果的影响,为科学养羊提供依据,选取3月龄体格、体重相近的小尾寒羊公羔100只,随机分为试验组和对照组,每组50只。试验组羔羊饲喂全价颗粒饲料,对照组采用传统的精、粗料混合饲喂技术,试验期75 d。试验结束时,比较2组羔羊的增重指标和饲料利用率指标,并进行养殖效益分析。结果表明,试验组肉羊的日增重、总增重、胴体重和屠宰率均显著高于对照组（P〈0.05）;试验组羔羊的饲料实际采食量较对照组显著提高（P〈0.05）,试验组羔羊的饲料损耗量较对照组显著降低（P〈0.05）,饲料利用率提高了4.36%,试验组羔羊的料肉比较对照组显著降低（P〈0.05）;试验组单只羔羊育肥的纯收入显著高于对照组（P〈0.05）。在肉羊育肥过程中,饲喂全价颗粒饲料能显著提高羊只的生长速度和产肉性能,降低人工成本,减少饲料浪费,提高经济效益。     

Effect of sex and feeding system on feed intake, growth, and meat and carcass characteristics of fattening Assaf lambs

The effect of feeding system and sex on intake, growth and carcass and meat characteristics of Assaf fattening lambs was studied. Twenty four weaned Assaf lambs, half males and half females were used. After an adaptation period, lambs were randomly assigned to one of the two feeding systems studied. Control lambs received ad libitum commercial concentrate (70% barley, 22% soybean meal, 4.8% wheat, 0.5% bicarbonate, 2.7% mineral–vitamin premix) and barley straw. Free Choice lambs had ad libitum and separate access to whole barley grain and a protein supplement (73.3% soyabean meal, 16% wheat, 1.7% bicarbonate, 9% mineral–vitamin premix). Lambs were slaughtered at 25 kg LBW. Feed intake was not significantly affected by sex (P > 0.05) but Free Choice lambs showed higher dry mater intake than the Control lambs. Nevertheless, only males from the Free Choice group showed an improvement in feed efficiency rate (P < 0.05) and average daily gain (P < 0.01) relating to the Control lambs. Neither feeding system nor feeding system × sex interaction significantly affected non-carcass weight, fat depots, cold carcass weight, dressing percentage, main proportions of commercial cuts and meat characteristics (P < 0.05). As it was expected, female lambs showed a lower average daily gain and a higher feed conversion efficiency than male lambs (P < 0.001) which was related to a greater fat deposition. Meat characteristics were unaffected by sex, with the exception of longissimus lumborum fat content, which was higher in female lambs.The present results suggest that Free Choice feeding system might be suitable for intensively reared male lambs since improvements in daily weight gain and feed conversion rate were achieved, with no adverse effect on carcass and meat quality. Despite the selected diet of both, males and females, did not differ in the crude protein content, the use of Free Choice feeding system for female lambs did not improve performance compared to the Control group.     

Finishing of dairy steers having grazed semi-natural grasslands

The objective of this study was to determine the effects of initial live weight, level of grain feeding, and length of finishing period on weight gain and carcass traits of dairy steers that had grazed semi-natural grasslands. Steers were subdivided by initial live weight (low vs. high) and were fed two levels of grain (0.5% vs. 1.0% of live weight day^− 1) during three different lengths of finishing period (3, 5 vs. 8 months). In total, 192 steers, initially 18 to 21 months of age, were fed grass–clover silage ad libitum. Steers fed high levels of grain had a higher dietary feed intake than steers fed low levels of grain (10.5 vs. 9.7 kg DM day^− 1; P < 0.001). Carcass weight gain (630 g) was highest and feed conversion (169 MJ metabolizable energy per kg carcass gain) was best in steers with 5 months of finishing. Steers with low initial weights had a higher daily carcass weight gain than initially heavy steers (614 vs. 571 g, P = 0.013). A high initial weight and a long finishing period resulted in heavier and fatter carcasses with a higher conformation score and lower proportions of valuable retail cuts and bone. In conclusion, high-quality carcasses can be produced when finishing dairy steers that previously have grazed semi-natural grasslands. Performance and carcass traits were more effected by initial weight and length of finishing period than by level of grain feeding.     

The response of growing native turkeys to different feed colours and forms

A total number of 180 1‐day old native turkey chicks were chosen in this study, for evaluating the impacts of using different attracting colours and forms of the offered feed on growth performance, carcass traits and some of health aspects, in a 3 × 2 factorial experimental design. The birds were allocated into three main groups according to feed colour (non‐coloured, orange and green feeds), then each main group was divided to three subgroups corresponded to feed form (mash and crumbles feed) respectively. The obtained results indicated that feed colours and forms changed significantly the final body weight, body weight gain, feed conversion, gizzard percentage, meat juiciness, plumage conditions and mortality rate. However, there were no significant differences among the treatments in carcass traits, meat quality (percentages of heart, liver, abdominal fat colour, flavour and tenderness) and body temperature. Significant interactions of feed colours × forms groups were existed in most studied traits except in feed consumption, giblets, meat quality traits, plumage conditions and body temperature. Finally, considering the obtained results, it was observed that the native turkeys prefer green feed as crumbles over non‐coloured or mash feed. Consequently, feeds for turkey chicks should be in green mash or crumbles during the growing period to maximize the profit.     

Performance and carcass measurements of ewe lambs reared in a feedlot and fed wheat (<Emphasis Type="BoldItalic">Triticum durum</Emphasis> Desf.) middlings total mixed rations in the summer season

The effect of total mixed ratios containing wheat middlings (WM) as a corn grain substitute on the growth performance and carcass traits of Comisana ewe lambs was evaluated. Forty ewe lambs, with average live body weight of 13 ± 0.3 kg (mean ± SEM), were allocated randomly to two isocaloric and isonitrogenous diets for 50 days. Control diet contained 400 g/kg of dry matter (DM) of corn as the main starchy source, whereas experimental diet contained 600 g/kg DM of WM. In vivo nutrient apparent digestibility of the two diets was determined using Comisana rams (mean body weight, 65 ± 2.3 kg) and indicated significant (P < 0.05) differences for neutral detergent fibre, acid detergent fibre, cellulose and hemicellulose fractions. Results from the trial using Comisana ewe lambs showed that growth traits were unaffected by dietary treatments as well as none of the carcass measurements examined (P > 0.05). These findings indicate that WM results as a suitable feed ingredient for growing ewe lambs that can be a satisfactory substitute to conventional grain source.     

Effects of feeding different levels of cooked and sun dried fish offal on carcass traits of growing Rhode Island Red chicks

Fourteen days old Rhode Island Red chicks were used to evaluate effects of processed fish offal (fishmeal) on DM intake (DMI), body weight gain (BWG), feed conversion ratio (FCR = DMI/BWG) and carcass traits. Ten chicks were assigned to each of 3 replicates of 6 diets (T₁, T₂, T₃, T₄, T₅, T₆, containing 0, 3.32, 6.64, 9.96, 13.28 and 16.6% fishmeal, respectively, having 18.44–19.82% CP). After 77 days of ad-lib feeding, 3 male and 3 female chicks per treatment were fasted overnight, killed and body parts weighed. T₁ had lowest but T₆ highest (p ≤ 0.001) daily intakes of 68.5 and 77.0 g DM head⁻¹, 13.3 and 14.8 g CP head⁻¹ and 231 and 243 kcal ME head⁻¹, respectively. BWG (10.7 g head⁻¹ d⁻¹), FCR (6.79), weights of carcass (569 g), breast (160 g) and total edible (676 g) and dressing % (66%) of T₁ (0% fishmeal) was smaller (p ≤ 0.001) than those of fishmeal groups {12.8 to 13.5 g head⁻¹ d⁻¹; 5.83 to 6.35 g; 671 to 729 g; 196 to 219 g; 807 to 876 g and 67 to 68%, respectively}. Best results of BWG, FCR and carcass traits were obtained at 9.96% fishmeal inclusion level; however acceptable results could be obtained up to 12.5%.     

Effect of altering nutrient density (concentrate to roughage ratio) and restricting energy intake on rate, efficiency and composition of growing lambs

Two hundred ninety-eight Rambouillet ewe and wether lambs approximately 9 mo old from Texas were allotted to pens (29 to 30 lambs/pen). Two replicate pens were fed each of five diets. Two methods of restricting energy intake were evaluated: altering nutrient density (55% vs 72.5% vs 90% concentrate levels) and restricting intake of the 90% concentrate pelleted diet (92.5% or 85% ad libitum intake). Daily gains were highest with the 72.5% concentrate level and feed efficiency was poorest with the 55% concentrate diet fed ad libitum. Altering nutrient density did not reduce energy intake because lambs compensated by increasing feed intake at the lower nutrient densities. Actual feed intake was 89.5% of ad libitum for the 92.5% of ad libitum intake level and 84% of ad libitum at the 85% of ad libitum intake level due to refusal to consume some fines from the 90% concentrate diet. Feed refusal was greatest for lambs with ad libitum access to feed. Average daily gain was depressed by 8% at the 85% intake level. However, feed efficiency was improved (P less than .01) by 20% when intake was restricted to 92.5% of the ad libitum intake level. Differences in carcass traits were small, but consistent; carcass fat content was reduced slightly by restricting feed intake at constant slaughter weight.     

Effect of ractopamine hydrochloride and zilpaterol hydrochloride on growth,diet digestibility,intake and carcass characteristics of feedlot lambs

The effects of the β-adrenergic agonists ractopamine hydrochloride (RH; 0.35, 0.70 and 1.05 mg kg^− 1 of BW d^− 1) and zilpaterol hydrochloride (ZH; 0.10, 0.20 and 0.30 mg kg^− 1 of BW d^− 1) on growth performance and carcass characteristics were determined in 84 Dorper × Katahdin lambs (12 lambs per treatment), that were randomly assigned to a complete block design during a 42-day feeding trial. Lambs were fed a corn grain-based diet (18.71% CP and 12.9 MJ/kg ME). Nutrient digestibility of diets and blood serum metabolites were also determined. There were no significant (P > 0.05) differences in growth characteristics by effect of ZH or RH administration. However, lambs final weight, total weight gain and ADG increased linearly (P < 0.05) as levels of both β-adrenergic agonist increased. RH or ZH administration did not affect feed efficiency, diet digestibility or particular blood serum metabolites of lambs. Carcass characteristics of lambs consuming ZH were significantly better (P < 0.01) than RH or control lambs; RH produced significant linear response on carcass weight, dressing percentage, longissimus muscle area, carcass conformation and quality grade, and improved quadratically (P < 0.05) fat thickness and USDA yield grade of lamb carcasses. On the other hand, increasing levels of ZH decreased linearly (P > 0.01) fat thickness and improved (P > 0.05) USDA yield grade and carcass quality grade. Both β-adrenergic agonists improved carcass characteristics; although greater improvements were obtained with ZH than RH for most carcass characteristics.     

Genetic relationships between pelt quality, maternal ability, and lamb production in the Gotland sheep breed

The aim of the present investigation was to study the genetic relationships between pelt quality traits (shade of fleece, size of curl, score for fleece colour, score for curl, score for quality of hair, score for thickness of fleece, sum of pelt scores, and overall score) on one hand and maternal ability, live weight, and carcass traits on the other hand for the Gotland sheep breed. Data were received from the Swedish Sheep Recording Scheme and included observations on 4-month weight (4MW) and pelt quality for 51,402 lambs and on weight (CW), fatness (FAT), and fleshiness (FLESH) of the carcass for 12,440 lambs. The lambs were born during the period 1991–2003. When maternal genetic and permanent environmental effects were included in the model direct heritabilities for the pelt quality traits varied between 0.16 and 0.25. Maternal heritabilities (0.01 to 0.05) and common environmental variances as a fraction of the total phenotypic variances (0.07 to 0.10) were low. Maternal heritabilities were higher for 4MW (0.11) and CW (0.12) than for the pelt quality traits. Direct-maternal genetic correlations were both for the pelt quality traits and for 4MW and CW generally negative and low to medium high. Direct genetic correlations between pelt quality traits on one hand and 4MW, CW, FAT or FLESH on the other hand were low (− 0.16 to 0.12). Maternal genetic correlations between pelt quality traits and 4MW or CW were positive and high (0.38 to 0.96). It was concluded that breeding for increased growth and improved carcass quality would not influence pelt quality negatively or vice versa. If maternal genetic effects are considered for 4MW and CW in the breeding program for the Gotland sheep breed, selection for maternal effects on 4MW and CW will have positive effects both on lamb weight and pelt quality.     

Carcass tissue composition in light lambs: Influence of feeding system and prediction equations

Fourty-eight Churra Tensina single male lambs were used to evaluate the effect of different feeding systems on carcass composition and predict the carcass tissue composition from joint composition and carcass measurements. Four treatments were studied: GR, unweaned lambs continuously grazing with ewes; GR + S, the same as the previous group, but lambs had free access to concentrate; DRL-GRE, lambs remained indoors with free access to concentrate and ewes grazed for 8 h/day, thereafter remaining with lambs; and DRL, lambs and ewes were kept in confinement, they had free access to concentrate and dry unifeed respectively. In the DRL-GRE and DRL groups lambs were weaned when 45 days old. Lambs were slaughtered at 22–24 kg live weight. Commercial joints from the half left carcass were obtained, recorded and dissected to determine carcass tissue composition.The feeding system had an effect on the proportion of the carcass tissue composition. GR treatment showed higher muscle (M) (p < 0.05) and bone (B) (p < 0.001) percentages, and a lower total fat (F) percentage (p < 0.001) than the rest of treatments. Hence it revealed higher M/F (p < 0.01) and lower M/B (p < 0.05) and subcutaneous fat/intermuscular fat ratios (SF/IF; p < 0.001). Carcass composition predictions were more accurate for grams than for percentages. In predictions from joint composition, pelvic limb was the most accurate joint for grams (R² = 0.84, R² = 0.68, and R² = 0.77 for muscle, bone, and fat, respectively) as well as for percentage (R² = 0.65, R² = 0.56, and R² = 0.73 for muscle, bone, and fat, respectively). Predictions from carcass measurements were greater in muscle and fat grams (R² = 0.87 and R² = 0.86 for muscle and fat, respectively) than in percentage (R² = 0.58 and R² = 0.73 for muscle and fat, respectively). Equations to predict carcass tissue that include carcass measurements are a simple method to assess accurately saleable muscle yield from different lamb feeding systems without involving carcass damage.