Prediction of physical characteristics of the lamb carcass using in vivo bioimpedance analysis

The increase of sheep meat competitiveness in international markets can be attributed to the rise of the quantity and the improvement of the quality of the edible portion of sheep carcasses. Usually, carcass yield is established after the slaughter of the animals. Yet, when carcass yield is determined in vivo, it can be both a costly and subjective method. This study proposes models for predicting the physical characteristics of lamb carcass using bioimpedance analysis (BIA) in live animals. Thirty-one Texel × Ile de France crossbreed ram lambs were slaughtered at 20, 26, 32 or 38 kg of BW. Before the slaughter, values of resistance (Rs) and reactance (Xc) were collected using a single-frequency BIA equipment (Model RJL Quantum II Bioelectrical Body Composition Analyzer). Then, BIA main variables such as body bioelectrical volume (V), phase angle (PA), resistive density (RsD) and reactive density (XcD) were calculated. After slaughter, cold carcass weight (CCW), cold carcass yield (CCY), subcutaneous fat thickness (SFT), soft tissue weight (STW) and soft tissue yield (STY) were also measured. Multiple regression analyses were carried out using the physical characteristics as dependent variables and the bioimpedance values as independent variables. Predictive performance of the models was assessed using leave-one-out cross-validation. The prediction model of CCW was obtained using the V, PA and RsD (R² = 0.97), STW through the V, RsD and XcD (R² = 0.97), CCY by Rs, Z and XcD (R² = 0.69), STY by V and XcD (R² = 0.67), and SFT only for XcD (R² = 0.84). The results indicated that BIA has the potential to predict carcass characteristics of lambs at different body masses.     

Effect of age and carcass weight on quality traits of m. rectus abdominis from Charolais heifers

In practice cattle may be slaughtered at different combinations of age and weight. As each of these factors could affect meat quality traits, the present work aimed to identify which combination can be expected to increase overall meat quality of m. rectus abdominis of Charolais heifers. Totally, 40 heifers were slaughtered either at 26±1 or at 36±1 months of age. Young heifers were sampled at two different carcass weights (349±12 and 394±8 kg). Old heifers were also sampled at two different carcass weights (397±6 and 451±9 kg). The m. rectus abdominis was excised 24 h postmortem to determine metabolic enzyme activities, myosin heavy-chain isoform proportions, lipid contents, collagen content and collagen solubility. Shear force measurements were evaluated on raw and broiled meat after 14 days of ageing. Meat quality traits scored between 0 and 10 by sensory analysis. Increasing slaughter age from 26 to 36 months had no impact on either raw/broiled shear force (0.31⩽P⩽0.47) and/or meat quality traits (0.62⩽P⩽0.91) or on physicochemical properties of heifer’s meat samples. Increasing carcass weight for a similar slaughter age of 26 months had also impact neither on meat quality traits (0.52⩽P⩽0.91) nor on muscular properties. On the contrary, increasing carcass weight for a similar slaughter age of 36 months had induced a decrease of muscular shear force (raw muscle; P=0.009) and a concomitant decrease of total collagen content (P=0.03). Nevertheless, no significant impact on meat quality traits was revealed by the sensorial panel (0.13⩽P⩽0.49). Metabolic enzyme activities (0.13⩽P⩽0.86) and myosin heavy-chain proportions (0.13⩽P⩽0.96) were not significantly impacted by slaughter age and carcass weight. Thus, the impact of increasing carcass weight and/or slaughter age in young Charolais heifers has a limited impact on meat quality traits and associated muscular characteristics. Modulating heifer’s cycles (age and/or carcass weight in the studied range) appears to be a way to answer to the numerous marketing chains, without penalising meat quality traits.     

Prediction of foal carcass composition and wholesale cut yields by using video image analysis

This work represents the first contribution for the application of the video image analysis (VIA) technology in predicting lean meat and fat composition in the equine species. Images of left sides of the carcass (n=42) were captured from the dorsal, lateral and medial views using a high-resolution digital camera. A total of 41 measurements (angles, lengths, widths and areas) were obtained by VIA. The variation of percentage of lean meat obtained from the forequarter (FQ) and hindquarter (HQ) carcass ranged between 5.86% and 7.83%. However, the percentage of fat (FAT) obtained from the FQ and HQ carcass presented a higher variation (CV between 41.34% and 44.58%). By combining different measurements and using prediction models with cold carcass weight (CCW) and VIA measurement the coefficient of determination (k-fold-R²) were 0.458 and 0.532 for FQ and HQ, respectively. On the other hand, employing the most comprehensive model (CCW plus all VIA measurements), the k-fold-R² increased from 0.494 to 0.887 and 0.513 to 0.878 with respect to the simplest model (only with CCW), while precision increased with the reduction in the root mean square error (2.958 to 0.947 and 1.841 to 0.787) for the hindquarter fat and lean percentage, respectively. With CCW plus VIA measurements is possible to explain the wholesale value cuts yield variation (k-fold-R² between 0.533 and 0.889). Overall, the VIA technology performed in the present study could be considered as an accurate method to assess the horse carcass composition which could have a role in breeding programmes and research studies to assist in the development of a value-based marketing system for horse carcass.     

Compensatory growth feeding strategy does not overcome negative effects on growth and carcass composition of low birth weight pigs

The aim of this study was to evaluate whether the compensatory growth feeding strategy could be a suitable solution for overcoming the negative effects on growth, carcass composition and meat quality of low birth weight pigs. Forty-two Swiss Large White barrows from 21 litters were selected at weaning and categorized into either being light (L; >0.8 and <1.3 kg) or heavy (H; >1.7 kg) birth weight pigs. From 27.8 kg BW, pigs were assigned within birth weight group to one of three feeding groups: AA: ad libitum access to the grower and finisher diet, RR: restricted access to the grower and finisher diet or RA: restricted access to the grower diet and ad libitum access to the finisher diet. At slaughter, the longissimus (LM) and semitendinosus (STM) muscles were removed from the right side of the carcass. Weight, girth and length of the STM and the LM area were determined after muscle excision. Carcass characteristics and meat quality traits were assessed. Using mATPase histochemistry, myofibre size and myofibre type distribution were determined in the LM and STM. Because of longer days on feed, total feed intake was greater (P<0.01) and feed efficiency was lower (P<0.01) in L than H barrows. Regardless of the birth weight group, AA and RA barrows grew faster (P<0.05) than RR barrows. During the compensatory growth period, RA barrows grew faster (P<0.05) than AA or RR barrows. Growth efficiency did not differ between RA and RR barrows but was greater (P<0.05) compared with AA barrows. Carcasses of L barrows were fatter as indicated by the lower (P⩽≤0.05) lean meat and greater (P⩽0.02) omental and subcutaneous fat percentage. Lean meat percentage was lower (P⩽0.05) in AA and RA than RR barrows. These differences caused by ad libitum feed access tended to be greater (feeding regime × birth weight group interaction; P<0.08) in L than H barrows. In L barrows, slow oxidative, fast oxidative glycolytic and overall average myofibre size of the LM and the fast glycolytic myofibres and overall average myofibre size of the dark portion of the STM were larger (P⩽0.03) than in H barrows. The study revealed that the compensatory growth feeding strategy was inadequate in overcoming the disadvantages of low birth weight.     

Dried artichoke bracts in rabbits nutrition: effects on the carcass characteristics,meat quality and fatty-acid composition

In this study, the effects of the inclusion of artichoke bracts (AB) in rabbit diets on the carcass characteristics and rabbit meat quality were studied. A total of 120 rabbits aged 38 days were used and divided into three groups that were fed with different isonitrogenous and isocaloric diets supplemented with AB at 0%, 5% and 10%. The animals were single housed in wire cages at a temperature of 22±2°C and had free access to clean drinking water. At 96 days of age, 12 rabbits/group were slaughtered in an experimental slaughterhouse without fasting. The carcass was weighed and the weights of the skin and full gastrointestinal tract were recorded. Carcasses were chilled at +4°C for 24 h in a refrigerated room. The chilled carcass weight (CCW), dressing out percentage (CCW as percentage of slaughter weight), and the ratio of the head and liver were determined as a percentage of CCW. The reference carcass weight was also calculated. Carcasses were halved and the two longissimus dorsi (LD) muscles were excised. The left LD muscle was divided into two parts. The fore part was used to measure pH, colour and cooking losses. The hind part of the left LD was vacuum-packed, frozen at –20°C and then freeze-dried. Proximate composition, fatty-acid profile and thiobarbituric acid-reactive substances values were determined on freeze-dried samples. Results showed that carcass characteristics, LD muscle traits and its oxidative status were not affected by the AB supplementation, except for the meat ether extract content that increased from 0.68% to 0.94% on fresh matter basis with the increase of the AB supplementation (P<0.01). The α-linolenic acid proportion decreased with the increase of the AB supplementation from 3.58% to 2.59% in the LD muscle and from 4.74% to 3.62% in the perirenal fat, whereas the n-6/n-3 ratio increased significantly with increasing AB inclusion from 7.15 to 10.20 in the LD muscle and from 6.68 to 9.35 in the perirenal fat (P<0.01). Furthermore, no significant difference was found in preference among meat samples from each group. The enrichment of the rabbit’s diet with AB allows the production of rabbit meat with a good degree of unsaturation and low saturation, even if the n-6/n-3 ratio was slightly worse.     

Effects of floor type,stocking density,slaughter age and gender on productive and qualitative traits of rabbits reared in collective pens

At 34 days of age, 376 crossbred rabbits of both sexes were housed in 16 open-top collective pens (1.68 m²) according to a 2×2×2 factorial arrangement with two types of pen floor (plastic v. wooden slatted), two stocking densities (12 v. 16 animals/m²) and two slaughter ages (76 v. 83 days). The rabbits were examined for growth performance, slaughter results and meat quality. The effect of gender was also examined. The percentage of rabbits with wounds due to aggression varied with stocking density (8.2% v. 26.2% for 12 v. 16 animals/m²; P⩽0.001), slaughter age (15.0% v. 22.0% at 76 v. 83 days; P⩽0.10) and gender (11.3% v. 25.8% for females v. males; P⩽0.001). Rearing rabbits on a plastic rather than a wooden slatted floor promoted slaughter weight (2795 v. 2567 g; P⩽0.001), dressing percentage (61.4% v. 60.9%; P⩽0.01), dissectible fat (2.4% v. 2.0%; P⩽0.01) and hind leg muscle-to-bone ratio (5.81 v. 5.35; P⩽0.001). Increased stocking density impaired daily growth (38.5 v. 35.9 g/day; P⩽0.05) and feed intake (140 v. 134 g/day; P⩽0.01) during the second period (55 days to slaughter) and decreased slaughter weight (2725 v. 2637 g; P⩽0.01). At the older slaughter age, the feed conversion ratio was impaired (2.98 v. 3.18; P⩽0.001); the slaughter weight (2574 g v. 2788 g; P⩽0.001), dissectible fat (2.0% v. 2.4%; P⩽0.01) and hind leg muscle-to-bone ratio (5.41 v. 5.75; P⩽0.01) increased; meat thawing losses, cooking losses and shear force decreased (P⩽0.05). The main differences between the females and males were found in the slaughter for transport losses (2.6% v. 2.2%; P⩽0.01) and longissimus lumborum proportions (13.0% v. 12.4%; P⩽0.01). In conclusion, the growth performance of pen-housed rabbits was largely determined by the type of floor and less affected by stocking density. The meat quality depended on ontogenetic factors, such as slaughter age and gender, and not on housing conditions. The differences in the percentages of wounded animals owing to experimental factors deserve further investigation from the perspective of animal welfare issues.     

Effects of whole linseed and rumen-protected conjugated linoleic acid enriched diets on beef quality

Instrumental assessments and sensory tests were performed to evaluate the effects of diet and postmortem ageing time (1, 7 and 21 days) on beef quality. A total of 48 Friesian calves were randomly allocated to four dietary treatments: control, whole linseed (10% linseed), conjugated linoleic acid (CLA) (2% protected CLA), and whole linseed+CLA (10% linseed and 2% protected CLA). Animals were slaughtered at 458±16.6 kg live weight and 11 months of age. Ageing was more significant than diet on most instrumental parameters. Meat from linseed enriched diets had greater drip loss (P⩽0.001) and intramuscular fat (P⩽0.01) than meat from animals fed CLA. Beef aged for 7 and 21 days had lower cooking losses (P⩽0.01) and shear force (P⩽0.001) than beef aged for 1 day. Lightness was affected only by display time. The addition of CLA in the diet increased hue and yellowness, whereas the inclusion of linseed decreased these values, as well as increased redness. Linseed in the diet decreased fat odour (P⩽0.05), but increased beef (P⩽0.01) and liver (P⩽0.05) flavours. Meat aged for 21 days was significantly more rancid (P⩽0.001), even under vacuum storage. Several organoleptic properties were improved with the inclusion of linseed in the diet, whereas they remained unaffected by the inclusion of CLA.     

Effect of oak acorn level on colostrum composition and plasma immunoglobulin G of late-pregnant goats and their kids

Oak acorn contains high levels of tannins which have capacity to form complexes with proteins and consequently reduce their availability and as a result it could reduce colostrum quality and immunoglobulin (Ig) synthesis. Thus, the aim of this experiment was to investigate the effects of dietary oak (Quercus persica) acorn (OA) level during the last 60 days of pregnancy on colostrum composition and plasma metabolites and IgG level of goats and their kids. In all, 24 multiparous pregnant goats (41.7±2.3 kg BW) were assigned into one of the three experimental diets consisted of control diet (without OA) and diets containing 20% (OA₂₀) or 40% (OA₄₀) OA on dry matter basis. Goats fed OA₄₀ had lower BW change compared with other groups (P⩽0.05). Kids birth weight was not affected by experimental diets (P>0.05). Goats fed OA containing diets had lower plasma glucose, triglyceride and Fe concentrations compared with those fed the control diet (P<0.01). Plasma IgG (P<0.01) and urea (P<0.05) concentrations were lower in goats fed OA₄₀ compared with others. Animals fed OA containing diets had higher plasma alanine aminotransferase than those fed the control diet (P<0.05). Goats fed OA₄₀ produced colostrum with lower fat (P⩽0.05) and lactose (P<0.01) contents compared with other animals. Goats fed OA containing diets had lower colostrum IgG level than those fed the control diet (P⩽0.05). Kids plasma total protein concentration was not affected by experimental diets (P>0.05), whereas kids born from goats fed OA containing diets had lower plasma IgG level compared with the control diet (P<0.01). It is concluded that feeding OA during the last 60 days of pregnancy decreased colostrum quality which may have adverse effect on kid’s survival.     

Intramuscular fat in lamb muscle and the impact of selection for improved carcass lean meat yield

Intramuscular fat percentage (IMF%) has been shown to have a positive influence on the eating quality of red meat. Selection of Australian lambs for increased lean tissue and reduced carcass fatness using Australian Sheep Breeding Values has been shown to decrease IMF% of the Muscularis longissimus lumborum. The impact this selection has on the IMF% of other muscle depots is unknown. This study examined IMF% in five different muscles from 400 lambs (M. longissimus lumborum, Muscularis semimembranosus, Muscularis semitendinosus, Muscularis supraspinatus, Muscularis infraspinatus). The sires of these lambs had a broad range in carcass breeding values for post-weaning weight, eye muscle depth and fat depth over the 12^th rib (c-site fat depth). Results showed IMF% to be highest in the M. supraspinatus (4.87±0.1, P<0.01) and lowest in the M. semimembranosus (3.58±0.1, P<0.01). Hot carcass weight was positively associated with IMF% of all muscles. Selection for decreasing c-site fat depth reduced IMF% in the M. longissimus lumborum, M. semimembranosus and M. semitendinosus. Higher breeding values for post-weaning weight and eye muscle depth increased and decreased IMF%, respectively, but only in the lambs born as multiples and raised as singles. For each per cent increase in lean meat yield percentage (LMY%), there was a reduction in IMF% of 0.16 in all five muscles examined. Given the drive within the lamb industry to improve LMY%, our results indicate the importance of continued monitoring of IMF% throughout the different carcass regions, given its importance for eating quality.     

Growth and Carcass Composition in Broiler-Type Chickens Following Passive Immunization of Insulin-Like Growth Factor-2 (IGF-2) Between 2 and 4 Weeks of Age

Ten broiler-type chickens at 2 weeks of age were injected daily with 0.5 ml of normal sheep serum while 10 others were similarly injected with 0.5 ml of a sheep anti-IGF-2 serum. Immunization with anti-IGF-2 serum had no significant effect upon body weight gain, on carcass composition, on appetite or food conversion. Liver weight was significantly increased (P < 0.05) in the anti-IGF-2 birds, but there was no effect on the weight of any other organ measured. The proportion of breast muscle in the carcass of anti-IGF-2 treated birds was significantly lower (P < 0.01) than in the controls and they also had 27% less abdominal fat. In acute studies, anti-IGF-2 administration caused an elevation in plasma GH, but in the longer term neither plasma GH nor plasma T₃ concentrations were significantly affected by immunization against IGF-2. These results suggest that circulating IGF-2 is not a major regulator of overall somatic growth in chickens, but may have an effect on muscle and fat deposition.     

Effect of production system before the finishing period on carcass,meat and fat qualities of beef

Twenty Gascon young bulls that had been reared either in intensive conditions (INT) (n=10) with early weaning at 3 to 4 months, or in a traditional extensive (EXT) system (n=10) with weaning at 7 months, were subjected to the same conditions during the 145-day finishing period. Production system before the finishing period did not affect conformation, dressing percentage or morphology of the carcass; nevertheless, tissue composition differed somewhat between the two groups. Display had a stronger effect on meat colour than did production system. Percentage of myoglobin was highest in INT (P⩽0.001), although meat texture and sensory quality did not differ between rearing conditions. EXT animals had darker, more yellow fat, a higher percentage of n-3 fatty acids (P⩽0.001), a lower percentage of saturated fatty acids (P⩽0.05) and a lower n-6/n-3 index (P⩽0.001) than did the INT-reared animals. Production system before the fattening period might modify some of the characteristics of commercial beef, especially those associated with fat.     

Passive immunization of insulin-like growth factor (IGF)-1 and of IGF-1 and IGF-2 in chickens

The effects of passive immunization against IGF-1 either alone, or together with immunization against IGF-2, on growth and metabolism were examined in chickens. Immunization against IGF-1 alone had no effect upon any aspect of growth, carcass composition, efficiency of energy utilization or hormone concentrations studied. Immunization against both IGF-1 and IGF-2 together resulted in a lighter final body weight (P < 0.05) compared with controls. Immunization against both IGFs together decreased abdominal fat content (P < 0.05) and resulted in a heavier mean spleen weight (P < 0.01). The joint immunization was also associated with elevated plasma T₃ concentrations. These data may indicate a role for IGF-2, but not for IGF-1, in fat metabolism in chickens.     

Genetic analysis of an F2 intercross between two strains of Japanese quail provided evidence for quantitative trait loci affecting carcass composition and internal organs

The purpose of this study was to identify genomic regions, quantitative trait loci (QTL), affecting carcass traits on chromosome 1 in an F2 population of Japanese quail. For this purpose, two white and wild strains of Japanese quail (16 birds) were crossed reciprocally and F1 generation (34 birds) was created. The F2 generation was produced by intercrossing of the F1 birds. Phenotypic data including carcass weight, internal organs and carcass parts were collected on F2 animals (422 birds). The total mapping population (472 birds) was genotyped for 8 microsatellite markers on chromosome 1. QTL analysis was performed with interval mapping method applying the line-cross model. Significant QTL were identified for breast weight at 0 (P < 0.01), 172 (P < 0.05) and 206 (P < 0.01), carcass weight at 91 (P < 0.05), carcass fatness at 0 (P < 0.01), pre-stomach weight at 206 (P < 0.01) and uropygial weight gland at 197 (P < 0.01) cM on chromosome 1. There was also evidence for imprinted QTL affecting breast weight (P < 0.01) on chromosome 1. The proportion of the F2 phenotypic variation explained by the significant additive, dominance and imprinted QTL effects ranged from 1.0 to 7.3 %, 1.2 to 3.3 % and 1.4 to 2.2 %, respectively.     

Effect and mode of action of the Texel muscling QTL (TM-QTL) on carcass traits in purebred Texel lambs

TM-QTL is a quantitative trait locus (QTL) on ovine chromosome 18 (OAR18) known to affect loin muscling in Texel sheep. Previous work suggested that its mode of inheritance is consistent with paternal polar overdominance, but this has yet to be formally demonstrated. This study used purebred Texel sheep segregating for TM-QTL to confirm its presence in the chromosomal region in which it was first reported and to determine its pattern of inheritance. To do so, this study used the first available data from a Texel flock, which included homozygote TM-QTL carriers (TM/TM; n=34) in addition to homozygote non-carriers (+/+; n=40 and, heterozygote TM-QTL-carriers inheriting TM-QTL from their sire (TM/+; n=53) or their dam (+/TM; n=17). Phenotypes included a wide range of loin muscling, carcass composition and tissue distribution traits. The presence of a QTL affecting ultrasound muscle depth on OAR18 was confirmed with a paternal QTL effect ranging from +0.54 to +2.82 mm UMD (s.e. 0.37 to 0.57 mm) across the sires segregating for TM-QTL. Loin muscle width, depth and area, loin muscle volume and dissected M. longissimus lumborum weight were significantly greater for TM/+ than +/+ lambs (+2.9% to +7.9%; P<0.05). There was significant evidence that the effect of TM-QTL on the various loin muscling traits measured was paternally polar overdominant (P<0.05). In contrast, there was an additive effect of TM-QTL on both live weight at 20 weeks and carcass weight; TM/TM animals were significantly (P<0.05) heavier than +/+ (+11.1% and +7.3%, respectively) and +/TM animals (+11.9% and +11.7%, respectively), with TM/+ intermediate. Weights of the leg, saddle and shoulder region (corrected for carcass weight) were similar in the genotypic groups. There was a tendency for lambs inheriting TM-QTL from their sire to be less fat with slightly more muscle than non-carriers. For example, carcass muscle weight measured by live animal CT-scanning was 2.8% higher in TM/TM than +/+ lambs (P<0.05), carcass muscle weight measured by carcass CT-scanning was 1.36% higher in TM/+ than +/+ lambs (P<0.05), and weight of fat trimmed from the carcass cuts was significantly lower for TM/+ than +/+ lambs (−11.2%; P<0.05). No negative effects of TM-QTL on carcass traits were found. Optimal commercial use of TM-QTL within the sheep industry would require some consideration, due to the apparently different mode of action of the two main effects of TM-QTL (on growth and muscling).     

Growth,meat and feed efficiency traits of lambs born to ewes submitted to energy restriction during mid-gestation

The objective of this study was to evaluate the effects of the energy restriction of gestation of adult ewes from day 45 to day 115 on lamb live performance parameters, carcass and meat traits. In experiment I, dietary energy was restricted at 70% of the metabolizable energy (ME) requirements, after which ewes were re-fed ad libitum until lambing. In experiment II, dietary energy was restricted at 60% of the ME requirements, and ewes were re-fed to ME requirements until lambing. All ewes grazed together from the end of the restriction periods to weaning. Lambs were weaned and lot fed until slaughter. Feed intake, weight gain and feed efficiency were recorded, and body fat thickness and ribeye area (REA) were measured in the longissimus thoracis muscle. After slaughter, carcass weight and yield, fat depth, carcass and leg length, and frenched rack and leg weights and yields were determined. Muscle fiber type composition, Warner-Bratzler shear force, pH and color were determined in the longissimus lumborum muscle. In experiment I, energy restriction followed by ad libitum feeding affected lamb birth weight (P<0.05); however, no effects (P>0.05) were observed on later BW, REA, BF or carcass traits. Lambs born to non-restricted-fed ewes had higher (P<0.05) weight and yield of the frenched rack cut and their meat tended (P=0.11) to be tender compared with that of lambs from restricted ewes. The percentage of oxidative muscle fibers was lower for lambs born to non-restricted ewes (P<0.05); however, no effects of ewe treatment were observed on other muscle fiber types. For experiment II, energy restriction followed by ME requirements feeding, affected (P<0.01) pre-weaning live weight gain, weaning and final weights. Lambs from restricted ewes had higher (P<0.05) feed intake as % of leg weight and a trend to be less efficient (P=0.16) than lambs from unrestricted dams. Ribeye area and BF were not influenced by treatment. Treatment significantly affected slaughter weight, but had no effects on carcass yield and traits or on meat traits. The results obtained in both experiments indicate submitting ewes to energy restriction during gestation affects the performance of their progeny but the final outcome would depend on the ewe’s re-feeding level during late gestation and the capacity of the offspring to compensate the in utero restriction after birth.     

Visceral organ weights,digestion and carcass characteristics of beef bulls differing in residual feed intake offered a high concentrate diet

This study examined the relationship of residual feed intake (RFI) with digestion, body composition, carcass traits and visceral organ weights in beef bulls offered a high concentrate diet. Individual dry matter (DM) intake (DMI) and growth were measured in a total of 67 Simmental bulls (mean initial BW 431 kg (s.d.=63.7)) over 3 years. Bulls were offered concentrates (860 g/kg rolled barley, 60 g/kg soya bean meal, 60 g/kg molasses and 20 g/kg minerals per vitamins) ad libitum plus 0.8 kg grass silage DM daily for 105 days pre-slaughter. Ultrasonic muscle and fat depth, body condition score (BCS), muscularity score, skeletal measurements, blood metabolites, rumen fermentation and total tract digestibility (indigestible marker) were determined. After slaughter, carcasses and perinephric and retroperitoneal fat were weighed, carcasses were graded for conformation and fat score and weight of non-carcass organs, liver, heart, kidneys, lungs, gall bladder, spleen, reticulo-rumen full and empty and intestines full, were determined. The residuals of the regression of DMI on average daily gain (ADG), mid-test metabolic BW (BW^0.75) and the fixed effect of year, using all animals, were used to compute individual RFI coefficients. Animals were ranked on RFI and assigned to high (inefficient), medium or low groupings. Overall mean ADG and daily DMI were 1.6 kg (s.d.=0.36) and 9.4 kg (s.d.=1.16), respectively. High RFI bulls consumed 7 and 14% more DM than medium and low RFI bulls, respectively (P<0.001). No differences between high and low RFI bulls were detected (P>0.05) for ADG, BW, BCS, skeletal measurements, muscularity scores, ultrasonic measurements, carcass weight, perinephric and retroperitoneal fat weight, kill-out proportion and carcass conformation and fat score. However, regression analysis indicated that a 1 kg DM/day increase in RFI was associated with a decrease in kill-out proportion of 20 g/kg (P<0.05) and a decrease in carcass conformation of 0.74 units (P<0.05). Weight of non-carcass organs did not differ (P>0.05) between RFI groups except for the empty weight of reticulo-rumen, which was 8% lighter (P=0.05) in low RFI compared with high RFI bulls. Regression analysis indicated that a 1 kg DM/day increase in RFI was associated with a 1 kg increase in reticulo-rumen empty weight (P<0.05). Of the visceral organs measured, the reticulo-rumen may be a biologically significant contributory factor to variation in RFI in beef bulls finished on a high concentrate diet.     

Selection for components related to body composition in mice: correlated responses

Summary Correlated responses were estimated in each of two replicate lines of mice selected within full-sib families for high (HF) or low (LF) 12-week epididymal fat pad weight as a percentage of body weight (epididymal fat pad percentage), or high (HL) or low (LL) 12-week hind carcass weight as a percentage of body weight (hind carcass percentage). Two replicate control lines (RC) were maintained. Correlated traits were measured in each of the 10 generations of selection. Realized (r_{G R}) and offspring-sire genetic correlations generally were in agreement. In HF and LF, 3–6 week postweaning gain (r_{G R} = 0.36±0.04) and feed intake (r_{G R} = 0.50±0.13) had positive correlated responses, but feed efficiency and feed intake/metabolic body size did not change. Positive correlated responses were found for subcutaneous fat pad percentage, body weight-adjusted subcutaneous fat pad weight and fat percentage in the hind carcass (r_{G R}'s were 1.04±0.13, 0.93±0.13 and 0.90±0.08). In the hind carcass, fat-free dry (protein + ash) percentage showed a small negative correlated response, and fat-free dry weight did not change. In HL and LL, the correlated responses for the above traits were generally opposite to those observed in HF and LF. Litter size, percentage of infertile matings, and preweaning mortality showed no consistent correlated responses in any of the lines, but an index of fitness combining the three traits showed a decrease in all four selection treatments.Paper no. 11057 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, 27695-7601. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products named, nor criticisms of similar ones not mentioned     

Effects of sire genotype on lamb performance at weaning in extensive sheep systems

A low finishing weight and poor carcass characteristics are major causes of lower incomes in extensive sheep flocks; however, the use of terminal sire crossbreeding would improve lamb performance and carcass traits under these conditions. The aim of this study was to evaluate sire breed effects on the performance of lambs born to Corriedale ewes in extensive sheep systems in Western Patagonia. A total of 10 Corriedale, 10 Dorset, nine Suffolk and seven Texel sires, 16 of which were under a genetic recorded scheme and 20 selected from flocks not participating in genetic improvement programmes, were used across six commercial farms for 2 successive years. Data were collected from 685 lambs of the four resulting genotypes. Overall, Corriedale lambs were 0.47 kg lighter at birth than crossbred lambs (P<0.001). Suffolk and Texel sired lambs required more assistance (P<0.01) at birth than Corriedale or Dorset sired lambs, with Suffolk sired lambs requiring the most assistance (8%). Ewes sired with Suffolk rams had larger (P<0.05) litters than ewes sired with Texel or Corriedale rams. Lamb live weight gain from birth to weaning was higher (P<0.001) in crossbred lambs compared with Corriedale lambs, therefore, crossbred lambs averaged 2.9 kg heavier BW (P<0.001) than Corriedale lambs. A significant sire breed x sire source interaction was detected for lamb live weight gain (P<0.05) and lamb live weight at weaning (P<0.01), showing that the heaviest lambs were from recorded sires, except for Suffolk crossbred lambs. Mortality rate to weaning was increased (P<0.05) in Suffolk cross lambs (31%), with Corriedale lambs showing the lowest (17%) mortality. Terminal sire breeds increased (P<0.001) cold carcass weight, with 13.8, 16.0, 15.2 and 14.9 kg for the Corriedale, Dorset, Suffolk and Texel sired lambs, respectively. Carcass length, kidney knob and channel fat, fat grade, grade rule and fat depth measurements were not affected by sire breed (P>0.05). Carcass conformation was higher in Texel sired lambs compared with Corriedale lambs (P<0.05), with Dorset and Suffolk sired lambs being intermediate. Crossbred lambs showed a greater (P<0.001) eye muscle than Corriedale. Commercial cuts were affected by sire breed, as a result of the Corriedale lambs being smaller and having lighter carcass than crossbred lambs. Significant improvement in lamb weights at weaning and carcass traits could be expected when using a terminal sire on Corriedale ewes in Western Patagonia. However, no advantages were detected with the use of recorded sires under these production systems.     

Interspecies differences in the empty body chemical composition of domestic animals

Domestication of animals has resulted in phenotypic changes by means of natural and human-directed selection. Body composition is important for farm animals because it reflects the status of energy reserves. Thus, there is the possibility that farm animals as providers of food have been more affected by human-directed selection for body composition than laboratory animals. In this study, an analysis was conducted to determine what similarities and differences in body composition occur between farm and laboratory animals using literature data obtained from seven comparative slaughter studies (n = 136 observations). Farm animals from four species (cattle, goats, pigs and sheep) were all castrated males, whereas laboratory animals from three species (dogs, mice and rats) comprised males and/or females. All animals were fed ad libitum. The allometric equation, Y = aX^b, was used to determine the influence of species on the accretion rates of chemical components (Y, kg) relative to the growth of the empty body, fat-free empty body or protein weights (X, kg). There were differences between farm and laboratory animals in terms of the allometric growth coefficients for chemical components relative to the empty BW and fat-free empty BW (P < 0.01); farm animals had more rapid accretion rates of fat (P < 0.01) but laboratory animals had more rapid accretion rates of protein, water and ash (P < 0.01). In contrast, there was no difference in terms of the allometric growth coefficients for protein and water within farm animals (P > 0.2). The allometric growth coefficients for ash weight relative to protein weight for six species except sheep were not different from a value of 1 (P > 0.1), whereas that of sheep was smaller than 1 (P < 0.01). When compared at the same fat content of the empty body, the rate of change in water content (%) per unit change in fat content (%) was not different (P > 0.05) across farm animal species and similar ash-to-protein ratios were obtained except for dogs. The fraction of empty body energy gain retained as fat increased in a curvilinear manner, and there was little variation among farm animals at the same fat content of the empty body. These findings may provide the opportunity to develop a general model to predict empty body composition across farm animal species. In contrast, there were considerable differences of chemical body composition between farm and laboratory animals.