Effects of a quantitative trait locus for increased muscularity on carcass traits measured by subjective conformation and fat class scores and video image analysis in crossbred lambs

A quantitative trait locus (QTL) for increased loin muscularity (TM-QTL) has previously been identified in purebred Texel sheep. Crossbred lambs born out of Mule ewes mated to heterozygous Texel sires for the TM-QTL were evaluated for a range of carcass traits. Lambs were genotyped and classified as carriers (n = 62) of a single copy of the TM-QTL and non-carriers (n = 49). In this study, the effects of the TM-QTL on carcass attributes were investigated using subjective classification scores for conformation and fatness, and measurements from a video image analysis (VIA) system. In addition, refined prediction equations to estimate weights of primal joints (leg, chump, loin, breast and shoulder) were obtained by calibrating the VIA system against computer tomography (CT) measurements in the loin region. The new refined prediction models increased the accuracy of prediction of all primal cuts on an average of 16% compared to previously derived standard VIA prediction equations. The coefficient of determination (R2) of the VIA system to predict in vivo CT measurements ranged from 0.39 to 0.72 for measurements of Musculus longissimus lumborum (MLL) area, width and depth, lumbar spine length, loin muscle volume and loin muscularity index. Using VIA estimates of CT-measured loin muscle traits, a significant increase in depth (+2.7%) of the MLL was found to be associated with the TM-QTL. Conformation and fatness scores and the shape of the carcass measured as individual lengths, widths and areas by VIA were not significantly influenced by the TM-QTL. Primal meat yields estimated using both standard and refined VIA prediction equations were not significantly affected by the TM-QTL. However, carcass 'compactness' was found to have significantly increased in carrier lambs. The weight of the dissected MLL estimated using VIA information was greater (+2.6%) for carriers compared to non-carriers. To conclude, neither the current industry carcass evaluation system for conformation and fatness nor the standard VIA system is able to identify the effect of the TM-QTL in the loin region in the moment. However, the calibration of the VIA system against CT measurements resulted in improved VIA prediction equations for primal meat yields and also showed moderate potential to estimate loin muscle traits measured by CT and to detect, partially, the effect of the TM-QTL on these traits.     

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).     

The effects of a loin muscling quantitative trait locus (LoinMAX™) on carcass and VIA-based traits in crossbred lambs

LoinMAX (LM) is a quantitative trait locus (QTL), which was found to be segregated in Australian Poll Dorset sheep, and maps to the distal end of sheep chromosome 18. LM-QTL was reported to increase Musculus longissimus dorsi area and weight by 11% and 8%, respectively. The aim of this study was to comprehensively evaluate the direct effects of LM-QTL in a genetic background typical of the stratified structure of the UK sheep industry, before it can be recommended for use in the United Kingdom. Crossbred lambs, either non-carriers or carrying a single copy of LM-QTL, were produced out of Scottish Mule ewes (Bluefaced Leicester × Scottish Blackface) artificially inseminated with semen from two Poll Dorset rams that were heterozygous for LM-QTL. Unexpectedly, one of these rams was also heterozygous for a QTL that affects the overall carcass muscling (MyoMAX™). This was accounted for by nesting MyoMAX™ status (carrier or non-carrier) within sire in the statistical analysis. Lambs were weighed and scanned by using X-ray computed tomography (CT) at an average age of 113 days. Ultrasound scan measurements, along with lamb weights, were taken at an average age of 140 days and lambs were then slaughtered. Carcasses were weighed and classified for fat cover and conformation scores, based on the Meat and Livestock Commission (MLC) carcass classification scheme, and then scanned by using a video image analysis (VIA) system. M. longissimus lumborum (MLL) width, as measured by CT scanning, was greater (P < 0.05) in lambs heterozygous for LM-QTL compared with non-carriers. MLL in LM-QTL carrier lambs was also significantly deeper, as measured by both ultrasound muscle depth at the third lumbar vertebrae (+3.7%; P < 0.05) and CT scanning at the fifth lumbar vertebrae (+3.4%; P < 0.01). Consequently, MLL area, was measured by using CT scanning, was significantly higher (+4.5%; P < 0.01) in lambs carrying a single copy of LM-QTL compared with non-carriers. Additional traits measured by CT, such as leg muscle dimensions, average muscle density and tissue proportions, were not significantly affected by LM-QTL. LM-QTL did not significantly affect total carcass lean or fat weights or MLC conformation and fat score classifications. Using previously derived algorithms, VIA could detect a significant effect of the LM-QTL on the predicted weight of saleable meat yield in the loin primal cut (+2.2%; P < 0.05), but not in the other primal cuts, or the total carcass.     

Effects of genotype and plane of nutrition on growth and carcass characteristics of lambs from hill sheep systems

The objective of this study was to determine the effect of lamb genotype and plane of nutrition on post-weaning lamb growth, and carcass characteristics in hill sheep systems. The lamb genotypes compared were as follows: purebred Scottish Blackface, Swaledale × Scottish Blackface, Cheviot × Scottish Blackface, Lleyn × Scottish Blackface and Texel × Scottish Blackface lambs. During the finishing period, lambs were allocated to a (i) low plane of nutrition (LP), based on a fixed allowance of dried grass pellets representing a grass-based system; (ii) high plane of nutrition (HP-cereal), with a diet consisting proportionately of 0.20 dried grass pellets : 0.80 cereal-based concentrate offered ad libitum; (iii) high plane of nutrition (HP-cereal/oil), with a diet consisting proportionately of 0.20 dried grass pellets : 0.80 cereal-based concentrate containing oilseed rape offered ad libitum. There were significant genotype × diet interactions for dry matter (DM) intake (P < 0.001), live weight gain (P < 0.05) and carcass gain (P < 0.05). On the LP diet, carcass gains were higher for Texel cross compared to Blackface and Swaledale cross lambs (P < 0.05). On both HP diets, carcass gains were lower in Blackface and Swaledale crosses compared with the Cheviot, Lleyn and Texel cross lambs (P < 0.01). Feed conversion efficiency, expressed in terms of carcass gain per unit of DM, was highest for Texel cross and Cheviot cross, lowest in Swaledale cross and Blackface and intermediate for Lleyn cross lambs (P < 0.001). Conformation classification was lowest for Swaledale cross (P < 0.05) and highest for Texel cross lambs (P < 0.001), whilst those of Blackface, Cheviot and Lleyn cross lambs were similar. Carcasses from Blackface and Lleyn cross lambs had higher fat classifications than Texel and Cheviot cross lambs (P < 0.01). Feed conversion efficiency was lowest with the LP diet compared with the HP diets, resulting in a 5-week longer finishing period and lower carcass weights, fat scores, dressing proportions and subcutaneous fat depth measurements. These results indicate that crossbreeding can have a major effect on lamb performance in the hill sheep sector. Feeding a HP increased lamb growth rates, particularly for high growth-potential genotypes, improved feed efficiency, shortened the finishing period but increased carcass fatness. Including oilseed rape in concentrate-based diets did not affect performance.     

Growth performance and carcass quality of fattening lambs from fat-tailed and tailed sheep breeds

The growth performance and carcass traits of two fat-tailed breeds (Chaal and Zandi) and their crosses with rams of a tailed breed (Zel) were compared. After weaning, the growth and feed consumption of male and female lambs fattened for 114 days were recorded. A total of 45 male and female lambs were slaughtered and the left side of the carcasses were cut into six pieces, and the lean meat, bone, subcutaneous and intermuscular fat were determined. Average daily gain and feed conversion ratio in crossbred lambs improved, but the differences with pure lambs were not significant. The average weight of shoulder, brisket and loin were higher in crossbred than pure breed lambs (P < 0.01). The percentage of protein in the carcass of Zel × Zandi lambs was significantly higher than Zandi lambs. The smaller size and lower weight of fat-tail in crossbred lambs were compensated by higher percentage of subcutaneous, intermuscular and internal fat. The fat-tailed breeds provided good quality lean meat in terms of lower percentage of intermuscular fat.     

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.     

Associations of PrP genotype with lamb production traits in three commercial breeds of British lowland sheep

The Ram Genotyping Scheme was launched in Great Britain in 2001 as part of the National Scrapie Plan and was devised to reduce and eventually eradicate classical scrapie susceptible genotypes from the national pedigree flock. Anecdotal claims from breeders suggest that sheep with more resistant PrP genotypes may have inferior phenotypes. In this study, we test this possibility for lamb production traits in three breeds of lowland sheep: Charollais (22 752 lambs), Poll Dorset (22 589 lambs) and Texel (23 492 lambs). Data were received from 50 breeders and comprised weights at birth, 8 weeks and scanning (from which average daily weight gain was derived), and ultrasonic muscle and fat depths. Animal (direct) genetic effects and up to three maternal effects were fitted in linear mixed models for each trait. Fitting either PrP genotype or number of copies of individual alleles carried as fixed effects allowed potential associations with the PrP gene to be assessed. There were no significant associations seen in the Poll Dorset breed; however, significant associations were found with the number of allele copies carried in the other two breeds included in this study. Charollais lambs carrying one copy of the VRQ allele had significantly (P < 0.01) greater ultrasonic muscle depth (0.58 mm) and fat depth (0.2 mm) than non-carriers. In the Texel breed, lambs with one ARR allele were significantly heavier than those with two or zero ARR alleles; heterozygous ARR lambs were 0.07 kg heavier at birth (P < 0.05), 0.42 kg heavier at 8 weeks (P < 0.01) and 0.17 kg heavier at scan weight (P < 0.01), than non-carriers. After Bonferroni corrections to adjust significance thresholds to account for the large number of independent comparisons made, all significant results remained so at P < 0.05 or greater, except for the ARR allele effect on birth weight in the Texel breed, which was no longer significant. These results compare favourably with others from studies on many continental breeds of sheep, published in recent years, and add credence to the conclusion that selection on PrP genotype is unlikely to have any noticeable impact on the measured growth and carcass traits in sheep.     

Reducing the level of nutrition of twin-bearing ewes during mid to late pregnancy produces leaner prime lambs at slaughter

The Australian prime lamb industry is seeking to improve lean meat yield (LMY) as a means to increasing efficiency and profitability across the whole value chain. The LMY of prime lambs is affected by genetics and on-farm nutrition from birth to slaughter and is the total muscle weight relative to the total carcass weight. Under the production conditions of south eastern Australia, many ewe flocks experience a moderate reduction in nutrition in mid to late pregnancy due to a decrease in pasture availability and quality. Correcting nutritional deficits throughout gestation requires the feeding of supplements. This enables the pregnant ewe to meet condition score (CS) targets at lambing. However, limited resources on farm often mean it is difficult to effectively manage nutritional supplementation of the pregnant ewe flock. The impact of reduced ewe nutrition in mid to late pregnancy on the body composition of finishing lambs and subsequent carcass composition remains unknown. This study investigated the effect of moderately reducing ewe nutrition in mid to late gestation on the body composition of finishing lambs and carcass composition at slaughter on a commercial scale. Multiple born lambs to CS2.5 target ewes were lighter at birth and weaning, had lower feedlot entry and exit weights with lower pre-slaughter and carcass weights compared with CS3.0 and CS3.5 target ewes. These lambs also had significantly lower eye muscle and fat depth when measured by ultrasound prior to slaughter and carcass subcutaneous fat depth measured 110 mm from the spine along the 12th rib (GR 12th) and at the C-site (C-fat). Although carcasses were ~5% lighter, results showed that male progeny born to ewes with reduced nutrition from day 50 gestation to a target CS2.5 at lambing had a higher percentage of lean tissue mass as measured by dual energy X-ray absorptiometry and a lower percentage of fat during finishing and at slaughter, with the multiple born progeny from CS3.0 and CS3.5 target ewes being similar. These data suggest lambs produced from multiple bearing ewes that have had a moderate reduction in nutrition during pregnancy are less mature. This effect was also independent of lamb finishing system. The 5% reduction in carcass weight observed in this study would have commercially relevant consequences for prime lamb producers, despite a small gain in LMY.     

Effects of dam breed and dietary source of n-3 polyunsaturated fatty acids on the growth and carcass characteristics of lambs sourced from hill sheep flocks

The objectives of this study were to investigate the effect of dietary lipid source on the growth and carcass characteristics of lambs sourced from a range of crossbred hill ewes. Over a 2-year period, 466 lambs representing the progeny of Scottish Blackface (BF × BF), Swaledale (SW) × BF, North Country Cheviot (CH) × BF, Lleyn (LL) × BF and Texel (T) × BF ewes were sourced from six commercial hill flocks and finished on one of four diets: grass pellets (GP), cereal-based concentrate (CC), CC enriched with oilseed rape (CR) and CC enriched with fish oil (CF). Dry matter intake (DMI) was highest (P < 0.001) in lambs offered GP; however, carcass weight gain (CWG) and feed conversion efficiency were higher (P < 0.001) in lambs fed concentrate-based diets. For lambs offered concentrate-based diets, DMI and live weight gain were lower (P < 0.001) for CF than CC or CR. Lambs with T × BF dams achieved a higher (P < 0.05) daily CWG and CWG/kg DMI than BF × BF, SW × BF or LL × BF dams. When lambs were slaughtered at fat score 3, CH × BF, LL × BF and T × BF dams increased carcass weight by 0.8 to 1.4 kg (P < 0.001) and conformation score (CS) by 0.2 to 0.4 units (P < 0.001) compared with BF × BF or SW × BF dams. However, breed effects on carcass conformation were reduced by 50% when lambs were slaughtered at a constant carcass weight. Diets CC and CR increased carcass weight by 0.8 to 1.6 kg (P < 0.001) and CS by 0.1 to 0.3 units (P < 0.001) compared with GP and CF. Both, dam breed and dietary effects on carcass conformation were associated with an increase (P < 0.001) in shoulder width of the lambs. Lambs fed CF and slaughtered at a constant carcass weight had more subcutaneous fat over the Longissumus dorsi (P < 0.05), Iliocostalis thoracis (P < 0.001) and Obliquus internus abdominis (P < 0.001) compared with those fed CC. However, these effects were removed when lambs were slaughtered at a constant fat score. At both endpoints, lambs from T × BF dams contained less (P < 0.05) perinephric and retroperitoneal fat than SW × BF or LL × BF dams fed GP or CC, respectively. The results from this study show that using crossbred ewes sired by CH, LL or T sires will increase carcass weight and improve carcass conformation of lambs sourced from hill flocks. Inclusion of oilseed rape in lamb finishing diets had only minor effects on performance compared with a standard CC but feeding fish oil or GP impacted negatively on lamb growth and carcass quality.     

Use of cold carcass weight and fat depth measurements to predict carcass composition of Rasa Aragonesa lambs

A total of 22 measurements of fat depth, taken along the 13th rib, 5–6th lumbar vertebra, 3–4th sacrum vertebra, and the 2nd, 2–3rd, 3rd, 3–4th, 4th, 4–5th sternebra of the breast bone, were taken on intact carcasses with a sharpened steel rule, and related to the carcass composition of 18 Rasa Aragonesa lambs. The objective was to study the accuracy of these different measurements for predicting carcass composition and possible value, in the process of carcass grading or classification of ‘Ternasco’ Aragón lambs. Cold carcass weight (CCW) accounted for 74% and 40% of the total variation of muscle weight and total carcass fat weight, respectively. The addition of 4 cm fat depth over the 13th rib from the left side accounted for a further 13% of muscle weight, and the addition of 4 cm fat depth over the 5–6th lumbar vertebra from the right side accounted for a further 29% of the variation of total carcass fat weight. Regarding different fat depots, CCW accounted for 49% and 31% of the total variation of the intermuscular fat and kidney and pelvic fat, respectively.

However, CCW alone only accounted for 21% (NS) of the total variation of subcutaneous fat weight, but the addition of 4 cm fat depth over the 13th rib from the right side or the addition of 4 cm fat depth over the 5–6th lumbar vertebra from the right side accounted for a further 47% of the subcutaneous fat variation. A comparison of the residual standard deviations (RSD) of the two measurements indicated that the fat depth over the 5–6th lumbar vertebra was more accurate for predicting subcutaneous fat. The highest precision, after CCW, for predicting intermuscular fat, was fat depth over the 13th rib from the left side, which accounted for a further 18% of total variation of this fat depot. Prediction of carcass composition was improved by the addition of fat depth measurements, assisting in the commercial classification of ‘Ternasco’ Aragón lambs.     

Dissecting total genetic variance into additive and dominance components of purebred and crossbred pig traits

The partition of the total genetic variance into its additive and non-additive components can differ from trait to trait, and between purebred and crossbred populations. A quantification of these genetic variance components will determine the extent to which it would be of interest to account for dominance in genomic evaluations or to establish mate allocation strategies along different populations and traits. This study aims at assessing the contribution of the additive and dominance genomic variances to the phenotype expression of several purebred Piétrain and crossbred (Piétrain × Large White) pig performances. A total of 636 purebred and 720 crossbred male piglets were phenotyped for 22 traits that can be classified into six groups of traits: growth rate and feed efficiency, carcass composition, meat quality, behaviour, boar taint and puberty. Additive and dominance variances estimated in univariate genotypic models, including additive and dominance genotypic effects, and a genomic inbreeding covariate allowed to retrieve the additive and dominance single nucleotide polymorphism variances for purebred and crossbred performances. These estimated variances were used, together with the allelic frequencies of the parental populations, to obtain additive and dominance variances in terms of genetic breeding values and dominance deviations. Estimates of the Piétrain and Large White allelic contributions to the crossbred variance were of about the same magnitude in all the traits. Estimates of additive genetic variances were similar regardless of the inclusion of dominance. Some traits showed relevant amount of dominance genetic variance with respect to phenotypic variance in both populations (i.e. growth rate 8%, feed conversion ratio 9% to 12%, backfat thickness 14% to 12%, purebreds-crossbreds). Other traits showed higher amount in crossbreds (i.e. ham cut 8% to 13%, loin 7% to 16%, pH semimembranosus 13% to 18%, pH longissimus dorsi 9% to 14%, androstenone 5% to 13% and estradiol 6% to 11%, purebreds-crossbreds). It was not encountered a clear common pattern of dominance expression between groups of analysed traits and between populations. These estimates give initial hints regarding which traits could benefit from accounting for dominance for example to improve genomic estimated breeding value accuracy in genetic evaluations or to boost the total genetic value of progeny by means of assortative mating.     

Associations of functional candidate genes derived from gene-expression profiles of prenatal porcine muscle tissue with meat quality and muscle deposition

Ten genes (ANK1, bR10D1, CA3, EPOR, HMGA2, MYPN, NME1, PDGFRA, ERC1, TTN), whose candidacy for meat-quality and carcass traits arises from their differential expression in prenatal muscle development, were examined for association in 1700 performance-tested fattening pigs of commercial purebred and crossbred herds of Duroc, Pietrain, Pietrain x (Landrace x Large White), Duroc x (Landrace x Large White) as well as in an experimental F(2) population based on a reciprocal cross of Duroc and Pietrain. Comparative sequencing revealed polymorphic sites segregating across commercial breeds. Genetic mapping results corresponded to pre-existing assignments to porcine chromosomes or current human-porcine comparative maps. Nine of these genes showed association with meat-quality and carcass traits at a nominal P-value of < or = 0.05; PDGFRA revealed no association reaching the P < or = 0.05 threshold. In particular, HMGA2, CA3, EPOR, NME1 and TTN were associated with meat colour, pH and conductivity of loin 24 h postmortem; CA3 and MYPN exhibited association with ham weight and lean content (FOM) respectively at P-values of < 0.003 that correspond to false discovery rates of < 0.05. However, none of the genes showed significant associations for a particular trait across all populations. The study revealed statistical-genetic evidence for association of the functional candidate genes with traits related to meat quality and muscle deposition. The polymorphisms detected are not likely causal, but markers were identified that are in linkage disequilibrium with causal genetic variation within particular populations.     

Analysis of single nucleotide polymorphisms variation associated with important economic and computed tomography measured traits in Texel sheep

Sheep are an important part of the global agricultural economy. Growth and meat production traits are significant economic traits in sheep. The Texel breed is the most popular terminal sire breed in the UK, mainly selected for muscle growth and lean carcasses. This is a study based on a genome-wide association approach that investigates the links between some economically important traits, including computed tomography (CT) measurements, and molecular polymorphisms in UK Texel sheep. Our main aim was to identify single nucleotide polymorphisms (SNP) associated with growth, carcass, health and welfare traits of the Texel sheep breed. This study used data from 384 Texel rams. Data comprised ten traits, including two CT measured traits. The phenotypic data were placed in four categories: growth traits, carcass traits, health traits and welfare traits. De-regressed estimated breeding values (EBV) for these traits together with sire genotypes derived with the Ovine 50 K SNP array of Illumina were jointly analysed in a genome wide association analysis. Eight novel chromosome-wise significant associations were found for carcass, growth, health and welfare traits. Three significant markers were intronic variants and the remainder intergenic variants. This study is a first step to search for genomic regions controlling CT-based productivity traits related to body and carcass composition in a terminal sire sheep breed using a 50 K SNP genome-wide array. Results are important for the further development of strategies to identify causal variants associated with CT measures and other commercial traits in sheep. Independent studies are needed to confirm these results and identify candidate genes for the studied traits.     

Effects of sire breed on ewe dystocia, lamb survival and weaned lamb output in hill sheep systems

A study was carried out on six hill farms, located in the main hill regions of Northern Ireland, over three breeding seasons to investigate the effect of sire breed on ewe dystocia, lamb survival and weaned lamb output. On each farm, groups of 26 to 40 purebred Scottish Blackface ewes (n = 3174) were crossed with Blackface, Swaledale, North Country Cheviot, Lleyn and Texel sires by natural service (year 1) and artificial insemination (years 2 and 3). Each of the mating groups was initially balanced for ewe age, live weight and condition score, and a total of 15 sires of each breed were used over the 3 years. In total, 2272 ewes were recorded at lambing, producing 3451 lambs, over the 3 years. Sire breed had a significant effect (P < 0.001) on lamb birth weight with Blackface and Swaledale the lowest and Texel the highest. The proportion of ewes with dystocia was higher with Texel sires compared with Lleyn, Swaledale and Blackface sires (P < 0.05). Ewes mated to Cheviot sires had more dystocia than those mated to Blackface and Swaledale sires (P < 0.05), while ewes mated to Lleyn sire breed had more dystocia (P < 0.05) than those mated to Blackface sire breed. Most of the incidence of dystocia was attributable to increased lamb birth weight (P < 0.001), and some to litter size (P < 0.05). Swaledale, Cheviot, Lleyn and Texel sire breeds increased the incidence of malpresentations (P < 0.05). Lamb live weight at weaning was higher with Texel- and Cheviot- and Lleyn-sired lambs compared with Blackface- and Swaledale-sired lambs (P < 0.01). The level of lamb mortality at birth was not affected by sire breed. However, lamb mortality at weaning was lower for Lleyn-sired lambs compared with the other lamb genotypes (P < 0.05). These results indicate that the use of sires from larger breeds, such as Lleyn and Texel, within the Blackface ewe flocks can increase lamb output, with no apparent detrimental effects on lamb mortality or ewe survival, but increased assistance at lambing will be required.     

Quantitative trait loci for carcass traits on pig chromosomes 4, 6, 7, 8 and 13

For 22 carcass traits, we identified 16 QTLs (based on data for pig resource population no. 214, including 180 F2 hybrids of 3 Yorkshire boars and 8 Meishan sows) and mapped them with the use of 39 microsatellite marker loci on chromosomes 4, 6, 7, 8 and 13. Five QTLs were highly significant (P < or = 0.01 at chromosome level): for skin weight (on chromosome 7 at SW1856 and on chromosome 13 at SW1495), skin percentage (on chromosome 7 between SW2155 and SW1856 and on chromosome 13 between SW1495 and SW520), and ratio of leg and butt to carcass (on chromosome 4 at SW1996). The remaining 11 QTLs were significant (P < or = 0.05 at chromosome level): for backfat thickness at shoulder, loin eye width, loin eye height, fat meat weight, lean meat weight, skin weight, bone weight, skin percentage, fat meat percentage, and ratio of lean meat to fat meat. The proportion of phenotypic variance explained by these QTLs ranged from 0.06% (QTL for loin eye width on chromosome 8 between SW1037 and SW1953) to 18.04% (QTL for ratio of lean meat to fat meat on chromosome 7 between SW252 and SW581). Seven of the QTLs reported here are novel.     

Feed deprivation in Merino and Terminal sired lambs: (2) the metabolic response under pre-slaughter conditions and impact on meat quality and carcass yield

Under current Australian industry pre-slaughter guidelines, lambs may be off feed for up to 48 h before slaughter. The purpose of this study was to examine what proportion of circulating metabolites at slaughter are due to stress and feed deprivation and if this response differs between Merino and Terminal genotypes. In addition the effect of feed deprivation on carcass weight and meat quality was examined. Jugular blood samples were collected from 88 Merino and Terminal sired lambs at rest and at slaughter following 24, 36 and 48 h of feed deprivation and plasma analysed for glucose, lactate, non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHOB). From the same carcasses hot carcass weight (HCWT) were measured as well as a suite of meat quality traits measured such as M. longissimus lumborum (loin) and M. semitendinosus pH at 24 h postmortem. Loin samples were also analysed for intramuscular fat content and Warner–Bratzer Shear Force. Merino sired lambs had a higher NEFA response compared to Terminal sired lambs at slaughter after 24, 36 and 48 h of feed deprivation, with NEFA levels up to 35% higher than previously reported in the same animals at rest in animal house conditions, whereas BHOB response to feed deprivation was not affected by sire type (P>0.05) and similar to previously reported at rest. In addition to the metabolic effects, increasing feed deprivation from 36 h was associated with a 3% reduction in HCWT and dressing percentage as well as causing increased ultimate pH in the M. semitendinosus in Merino sired lambs. Findings from this study demonstrate that Merino and Terminal sired lambs differ in their metabolic response to feed deprivation under commercial slaughter conditions. In addition, commercial feed deprivation appears to have a negative effect on ultimate pH and carcass weight and warrants further investigation.     

Predicting beef carcass composition using tissue weights of a primal cut assessed by computed tomography

The potential of the composition of the forerib measured by X-ray computed tomography (CT) as a predictor of carcass composition was evaluated using data recorded on 30 Aberdeen Angus and 43 Limousin crossbred heifers and steers. The left sides of the carcasses were split into 20 cuts, which were CT scanned and fully dissected into fat, muscle and bone. Carcass and forerib tissue weights were assessed by dissection and CT. Carcass composition was assessed very accurately by CT scanning of the primal cuts (adj-R2 = 0.97 for the three tissues). CT scanning predicted weights of fat, muscle and bone of the forerib with adj-R2 of 0.95, 0.91 and 0.75, respectively. Single regression models with the weights of fat, muscle or bone in the forerib measured by CT as the only predictors to estimate fat, muscle or bone of the left carcass obtained by CT showed adjusted coefficients of determination (adj-R2) of 0.79, 0.60 and 0.52, respectively. By additionally fitting breed and sex, accuracy increased to 0.85, 0.73 and 0.67. Using carcass and forerib weights in addition to the previous predictors improved significantly the prediction accuracy of carcass fat and muscle weights to adj-R2 values of 0.92 and 0.96, respectively, while the highest value for carcass bone weight was 0.77. In general, equations derived using CT data had lower adj-R2 values for bone, but better accuracies for fat and muscle compared to those obtained using dissection. CT scanning could be considered as an alternative very accurate and fast method to assess beef carcass composition that could be very useful for breeding programmes and research studies involving a large number of animals, including the calibration of other indirect methods (e.g. in vivo and carcass video image analysis).     

Intake,feeding behaviour,digestibility, performance,carcass characteristics and meat quality of lambs fed different levels of semi-purified glycerine in the diet

The aim of this study was to evaluate the effect of different inclusion levels of semi-purified glycerine in the diet of feedlot lambs on feeding behaviour, nutrient intake and digestibility, carcass characteristics, meat quality and in vitro degradability. Thirty-two Dorper × (Texel × Suffolk) crossbred intact male lambs (22.2 ± 5.51 kg) were fed glycerine (90% purity) at 0, 120, 240 or 360 g/kg dry matter (DM) in a total mixed ration with a roughage to concentrate ratio of 40:60 for 84 d. In vitro degradability was not affected by glycerine supplementation. Feeding behaviour and digestibility of DM, crude protein and fibre and production performance were similar among treatments. Ether extract digestibility was lower at the highest inclusion level. Glycerine level had no effect on ruminal pH, carcass characteristics and meat quality, except for subcutaneous fat thickness which was lower for lambs fed glycerine at 240 and 360 g/kg DM. Scores for unpleasant taste, unpleasant odour, succulence and softness of meat were not affected by dietary glycerine level. These data suggest that there are no adverse effects on carcass quality and performance when semi-purified glycerine is provided up to 360 g/kg DM in the diet of growing lambs fed a forage to concentrate ratio of 40:60.     

Is the establishment rate and fecundity of Haemonchus contortus related to body or abomasal measurements in sheep?

The relationship among parasitological parameters, abomasal size and body size measurements was investigated in lambs following an experimental infection with Haemonchus contortus. In total, 100 lambs from five different genotypes (German Merino (GM), Texel × GM, Suffolk × GM, German Blackhead Mutton × GM and Ile de France × GM) were experimentally infected with 5000 infective third stage larvae of H. contortus at the time of weaning at 12 weeks of age. Four and six weeks after infection, individual faecal samples were collected for estimation of faecal egg counts (FECs). Furthermore, wither height, shoulder width, heart girth, loin girth and body length were taken at 18 weeks of life. Lambs were slaughtered and necropsied 7 weeks post-infection, and worm counts, abomasal volume and surface area were determined. Positive correlations were found between different body size parameters, body weight and abomasal sizes. FEC and worm counts were not significantly correlated either with body size parameters or with abomasal size. The mean worm burden was higher in GM than in crossbred lambs. There was no significant difference in abomasal size between GM and crossbred lambs. The results suggest that the variations between animals in worm burden following an experimental infection with H. contortus (worm resistance) are not influenced by body size parameters or abomasal sizes. Therefore, other factors, including genetic-based differences in resistance, must cause these findings between and within breeds.     

Growth,carcass and cooked meat characteristics of lambs sired by Dorset rams heterozygous for the Callipyge gene and Suffolk and Texel rams

Dorset (D) rams heterozygous for the Callipyge gene were single—sire mated to non-carrier ewes to produce Callipyge heterozygous (CLPG, n = 49) and normal (D, n = 33) lambs. Suffolk (S) and Texel (T) rams were mated to similar ewes to produce non-carrier crossbred S (n = 55) and T (n = 52) lambs. Lambs were finished on a high-energy diet to a target live weight of 57 kg. Pre-slaughter weight was recorded for each lamb prior to its transfer and slaughter through a commercial facility. Hot carcass weight and kidney and pelvic fat (KPF) were recorded at slaughter. Chilled carcasses were measured then fabricated into trimmed retail cuts by plant personnel. Each cut was weighed, and two loin chops were collected from each carcass for later cooking. CLPG lambs had the highest dressing % (53.6 versus 49.8–50.6; P < 0.05). At the same cold carcass weight, CLPG lambs had larger longissimus muscle areas (19.5 cm² versus 14.0–15.2 cm² for the rest; P < 0.05), less KPF (0.9 kg versus 1.04–1.13 kg; P < 0.05), less carcass fat (P < 0.05 for all measures), shorter carcasses (60.7 cm versus 61.8–64.7 cm; P < 0.05), and heavier trimmed sirloins, legs, and shoulders than any other group (a11 P < 0.05). They were similar to S lambs in receiving the lowest mean USDA yield grade. CLPG carcasses had the highest proportion of carcass weight represented by trimmed cuts (70% versus 65.7–67.8% for the rest; P < 0.05), the highest proportion of trimmed cuts (62.2% versus 59.7–60.6% for the rest; P < 0.05) represented by the most valuable cuts (leg + loin + rack + sirloin), and the highest composite carcass value ($135.8 versus $125–129 for the rest; P < 0.05). CLPG lambs also produced loin chops with the highest mean Warner–Bratzler shear values (5.4 kg versus 2.8–2.9 kg for the rest; P < 0.05) and the highest % cooking loss (31% versus 29–29.6% for the rest; P < 0.05).