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Background The classical functions of the skeleton encompass locomotion, protection and mineral homeostasis. However, cell-specific gene deletions in the mouse and human genetic studies have identified the skeleton as a key endocrine regulator of metabolism. The bone-specific phosphatase, Phosphatase, Orphan 1 (PHOSPHO1), which is indispensable for bone mineralisation, has been recently implicated in the regulation of energy metabolism in humans, but its role in systemic metabolism remains unclear. Here, we probe the mechanism underlying metabolic regulation by analysing Phospho1 mutant mice. Results Phospho1−/− mice exhibited improved basal glucose homeostasis and resisted high-fat-diet-induced weight gain and diabetes. The metabolic protection in Phospho1−/− mice was manifested in the absence of altered levels of osteocalcin. Osteoblasts isolated from Phospho1−/− mice were enriched for genes associated with energy metabolism and diabetes; Phospho1 both directly and indirectly interacted with genes associated with glucose transport and insulin receptor signalling. Canonical thermogenesis via brown adipose tissue did not underlie the metabolic protection observed in adult Phospho1−/− mice. However, the decreased serum choline levels in Phospho1−/− mice were normalised by feeding a 2% choline rich diet resulting in a normalisation in insulin sensitivity and fat mass. Conclusion We show that mice lacking the bone mineralisation enzyme PHOSPHO1 exhibit improved basal glucose homeostasis and resist high-fat-diet-induced weight gain and diabetes. This study identifies PHOSPHO1 as a potential bone-derived therapeutic target for the treatment of obesity and diabetes.

The skeleton is recognised as a key endocrine regulator of metabolism. Here we show that mice lacking the bone mineralization enzyme PHOSPHO1 (Phospho1-/-) exhibited improved basal glucose homeostasis and resisted high-fat-diet induced weight gain and diabetes. The metabolic protection inPhospho1-/-mice was manifested in the absence of altered levels of osteocalcin. Osteoblasts isolated fromPhospho1-/-mice were enriched for genes associated with energy metabolism and diabetes;Phospho1both directly and indirectly interacted with genes associated with glucose transport and insulin receptor signalling. Canonical thermogenesis via brown adipose tissue did not underlie the metabolic protection observed in adultPhospho1-/-mice. However, the decreased serum choline levels inPhospho1-/-mice were normalized by feeding a 2% choline rich diet resulting in a normalization in insulin sensitivity and fat mass. This study identifies PHOSPHO1 as a potential therapeutic target for the treatment of obesity and diabetes.

Visible and near-infrared spectroscopy (Vis-NIRS) was tested for its effectiveness in predicting intramuscular fat (IMF) and WBSF in Nellore steers. Beef samples from longissimus thoracis, aged for either 2 or 7 days, had their spectra collected for wavelengths ranging from 400 to 1395 nm. Partial least squares regression models were developed for each trait. Determination coefficients of calibration models for WBSF ranged from 0.17 to 0.53. Considering WBSF in samples aged for 2 days, Vis-NIR correctly classified 100% of tough samples (>45 N), but wrongly classified all tender samples (≤45 N) as tough. Determination coefficients of calibration models for IMF ranged from 0.12 to 0.14. Vis-NIRS is a useful tool for identifying tough beef, but it is less effective in predicting tender samples and IMF. Additional studies are necessary to generate more robust models for the prediction of intramuscular fat in intact meat samples of Nellore cattle.

Computed tomography (CT) parameters, including spiral computed tomography scanning (SCTS) parameters, intramuscular fat (IMF) and mechanically measured shear force were derived from two previously published studies. Purebred Texel (n = 377) of both sexes, females (n = 206) and intact males (n = 171) were used to investigate the prediction of IMF and shear force in the loin. Two and three dimensional CT density information was available. Accuracies in the prediction of shear force and IMF ranged from R2 0.02 to R2 0.13 and R2 0.51 to R2 0.71 respectively, using combinations of SCTS and CT scan information. The prediction of mechanical shear force could not be achieved at an acceptable level of accuracy employing SCTS information. However, the prediction of IMF in the loin employing information from SCTS and additional information from standard CT scans was successful, providing evidence that the prediction of IMF and related meat eating quality (MEQ) traits for Texel lambs in vivo can be achieved.

Novel, multi-object X-ray computed tomography (CT) methodologies can individually analyse vacuum-packed meat samples scanned in batches of three or more, saving money and time compared to scanning live animals. If intramuscular fat (IMF), as a proxy for meat quality, can be predicted with similar accuracies as in live lambs, this method could be used to grade on quality, or to inform breeding programmes. Lamb loin cuts from commercial carcasses (n=303), varying in fat and conformation grade, were vacuum-packed and CT scanned, then tested for meat quality traits and by a trained taste panel. Tissue density values measured by CT, alongside carcass and loin weights, predicted IMF with moderate accuracy (R2 0.36), but did not accurately predict shear force or sensory traits. Juiciness and flavour increased linearly with IMF, whilst texture and overall liking increased to an optimum between 4 and 5% IMF. Samples predicted by CT as having >3% IMF scored significantly higher for sensory traits, than those predicted as

The study used visible and near-infrared spectroscopy (Vis-NIR) in a large commercial processing plant, to test a system for meat quality (intramuscular fat; IMF) data collection within a supply chain for UK lamb meat. Crossbred Texel x Scotch Mule lambs (n = 220), finished on grass on 4 farms and slaughtered across 2 months, were processed through the abattoir and cutting plant and recorded using electronic identification. Vis-NIR scanning of the cut surface of the M. longissimus lumborum produced spectral data that predicted laboratory-measured IMF% with moderate accuracy (R2 0.38–0.48). Validation of the Vis-NIR prediction equations on an independent sample of 30 lambs slaughtered later in the season, provided similar accuracy of IMF prediction (R2 0.54). Values of IMF from four different laboratory tests were highly correlated with each other (r 0.82–0.95) and with Vis-NIR predicted IMF (r 0.66–0.75). Results suggest scope to collect lamb loin IMF data from a commercial UK abattoir, to sort cuts for different customers or to feed back to breeding programmes to improve meat quality.

The hypothesis that pigs placed on diets with reduced indispensable amino acid (AA) content attempts to offset the reduction in the nutrient density with increased feed intake was tested. In the experiment, feeds with a high or a low AA content were administrated to pigs fed ad-libitum or restrictively according to a 2 × 2 factorial design. Ninety-six barrows were housed in 8 pens (12 pigs/pen) equipped with automatic feeders. Within pen, and from 47 body weight (BW) onwards, 6 pigs were fed ad libitum. The others pigs were allowed to consume, as a maximum, the feed amounts indicated by the breeding company feeding plane to optimize the feed efficiency. In early (86-118 kg BW) and late (118-145 kg BW) finishing, the pigs of 4 pens received feeds with high indispensable AA contents (8.1 and 7.5 g lysine/kg in the two periods, respectively). The other pigs received feeds with reduced indispensable AA contents (lysine, methionine, threonine and tryptophan) by 9 and 18% in early and late finishing, respectively. Body lipid and protein (Pr) retentions were estimated from BW and back-fat depth measures recorded at the beginning and the end of each period. Nitrogen excretion was estimated as actual intake minus estimated N-retention (Pr/6.25). Pigs were slaughtered at 144 kg BW. Restricted feeding decreased feed intake (-7%), daily gain (-5%), carcass weight (-2.6%) and back-fat depth (-8.0%) but increased gain:feed ratio (+2%). The AA restriction increased feed intake (+5.9%), carcass weight (+4.9%) and intramuscular fat (+17.6%), and reduced carcass weight variation (-36%), with no effects on the feed efficiency and the estimated Pr (142 g/d). N excreted was reduced by feed (-9%) and dietary AA (-15%) restrictions. Irrespectively of the feeding level, the pigs responded to a reduction of the dietary essential AA content by increasing their feed intake.

The aim of the study was to investigate if myostatin dysfunction would promote the gain in muscle mass and peak isometric force (P0 ) of soleus muscle (SOL) in response to functional overloading (FO) after ablation of the gastrocnemius muscle. Fifteen male Berlin high (BEH) mice homozygous for the compact mutation causing dysfunction of myostatin and 17 mice with the corresponding wild-type allele (BEH+/+) were subjected to FO of SOL for 28 days at the age of 14 weeks. Compared with BEH+/+ mice, SOL of BEH was heavier (mean ± SD, 13.5 ± 1.5 vs 21.4 ± 1.8 mg, respectively, P

Myostatin dysfunction promotes muscle hypertrophy, which can complicate assessment of muscle properties. We examined force generating capacity and creatine kinase (CK) efflux from skeletal muscles of young mice before they reach adult body and muscle size. Isolated soleus (SOL) and extensor digitorum longus (EDL) muscles of Berlin high (BEH) mice with dysfunctional myostatin, i.e., homozygous for inactivating myostatin mutation, and with a wild-type myostatin (BEH+/+) were studied. The muscles of BEH mice showed faster (P < 0.01) twitch and tetanus contraction times compared with BEH+/+ mice, but only EDL displayed lower (P < 0.05) specific force. SOL and EDL of age-matched but not younger BEH mice showed greater exercise-induced CK efflux compared with BEH+/+ mice. In summary, myostatin dysfunction leads to impairment in muscle force generating capacity in EDL and increases susceptibility of SOL and EDL to protein loss after exercise.

In order to assess the extent of genotype by environment interactions (G×E) and environmental sensitivity in sheep farm systems, environmental factors must be identified and quantified, after which the relationship with the traits(s) of interest can be investigated. The objectives of this study were to develop a farm environment (FE) scale, using a canonical correlation analysis, which could then be used in linear reaction norm models. Fine-scale farm survey data, collected from a sample of 39 Texel flocks across the United Kingdom, was combined with information available at the national level. The farm survey data included information on flock size and concentrate feed use. National data included flock performance averages for 21-week-old weight (21WT), ultrasound back-fat (UFD) and muscle (UMD) depths, as well as regional climatic data. The FE scale developed was then combined with 181 555 (21WT), 175 399 (UMD) and 175 279 (UFD) records from lambs born between 1990 and 2011, on 494 different Texel flocks, to predict reaction norms for sires used within the population. A range of sire sensitivities estimated across the FE scale confirmed the presence of genetic variability as both ‘plastic’ and ‘robust’ genotypes were observed. Variations in heritability estimates were also observed indicating that the rate genetic progress was dependent on the environment. Overall, the techniques and approaches used in this study have proven to be useful in defining sheep FEs. The results observed for 21WT, UMD and UFD, using the reaction norm models, indicate that in order to improve genetic gain and flock efficiency, future genetic evaluations would benefit by accounting for the G×E observed.

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.

For the consumer, tenderness, juiciness and flavour are often described as the most important factors for meat eating quality, all of which have a close association with intramuscular fat (IMF). X-ray computed tomography (CT) can measure fat, muscle and bone volumes and weights, in vivo in sheep and CT predictions of carcass composition have been used in UK sheep breeding programmes over the last few decades. This study aimed to determine the most accurate combination of CT variables to predict IMF percentage of M. longissimus lumborum in Texel lambs. As expected, predicted carcass fat alone accounted for a moderate amount of the variation (R(2)=0.51) in IMF. Prediction accuracies were significantly improved (Adj R(2)>0.65) using information on fat and muscle densities measured from three CT reference scans, showing that CT can provide an accurate prediction of IMF in the loin of purebred Texel sheep.

Previous work showed that the Texel muscling QTL (TM-QTL) results in pronounced hypertrophy in the loin muscle, with the largest phenotypic effects observed in lambs inheriting a single copy of the allele from the sire. As the loin runs parallel to the spinal vertebrae, and the development of muscle and bone are closely linked, the primary aim of this study was to investigate if there were any subsequent associations between TM-QTL inheritance and underlying spine characteristics (vertebrae number, VN; spine region length, SPL; average length of individual vertebrae, VL) of the thoracic, lumbar, and thoracolumbar spine regions. Spine characteristics were measured from X-ray computed tomography (CT) scans for 142 purebred Texel lambs which had been previously genotyped. Least-squares means were significantly different between genotype groups for lumbar and thoracic VN and lumbar SPL. Similarly for these traits, contrasts were shown to be significant for particular modes of gene action but overall were inconclusive. In general, the results showed little evidence that spine trait phenotypes were associated with differences in loin muscling associated with the different TM-QTL genotypes.

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

Carcass quality of 72 steers, 48 heifers and 21 bulls from continental and dairy genotypes were compared on the basis of conformation, fatness and saleable meat yield (SMY%) of the fillet and trimmed boneless sirloin cuts. Comparisons between genotype and gender groups showed that steers from beef breeds had higher EUROP conformation scores than those from dairy breeds which corresponded to a higher SMY% of sirloin and fillet. Results suggested that the EUROP grid may underestimate the sirloin SMY% of Charolais heifers due to their higher muscle-to-bone ratio. Furthermore, the 141 carcasses were used to assess the accuracy with which video image analysis (VIA) and visual classification in a commercial abattoir predicted the weight and SMY% of the sirloin and fillet. Both VIA and the visual carcass classification systems resulted in similar accuracies for prediction of sirloin SMY% (R2=58%, RSD=0.35% for VIA and R2=57%, RSD=0.35% for visual classification) but fillet yield was poorly predicted by both VIA and visual classification systems. Including the weight of excess fat removed during sirloin fabrication as an additional covariate for sirloin SMY% prediction did not offer any substantial improvement in predictive ability. Inclusion of bone weight as an additional covariate did show some promise for improving the prediction accuracy of fillet SMY%. The fact that no statistically significant correlations between fillet yield and EUROP carcass classification categories (assigned visually or by the VIA) could be identified after adjustment for genotype further justifies the need to consider alternative modes of carcass evaluation to better reflect the distribution of meat throughout the carcass.

Pigs with a lean genotype were fed diets differing in protein and amino acid contents between 40 and 115 kg live weight. A high protein control regime (C) was compared with one supplying 11% less total protein but the same essential amino acid levels (LP1) and one supplying 16% less protein but lower amino acid levels (LP2). Regime LP2 produced fatter pigs in terms of subcutaneous, intermuscular and intramuscular fat (IMF), the latter measured in longissimus and semimembranosus muscles. The percentage of linoleic acid was lowest and that of oleic acid highest in IMF from LP2 pigs (11.57 and 34.59% respectively in longissimus). Pigs in regime LP1 had more longissimus IMF than C but similar semimembranosus IMF although both muscles had lower percentages of linoleic acid in LP1 than C, suggesting a tendency towards greater fat deposition in LP1. The high IMF content in LP2 produced the most tender, juicy steaks.

The effects on compositional changes across the growing-finishing period (40-115 kg) of feeding pig diets with different protein and amino acid levels were investigated using CT scanning (at 60, 85 and 115 kg live weight). Pigs of a lean commercial genotype were fed a commercial control regime (C), or a low protein regime with either high (LP1) or low (LP2) essential amino acid levels, all balanced for net energy. In vivo CT measurements agreed well with post-slaughter sample joint dissection results for carcass tissue weights/proportions, and CT-measured muscle density predicted intramuscular fat accurately. Pigs on C and LP1 regimes did not differ significantly in composition during growth. However, pigs on the LP2 regime had significantly more fat (in carcass, internal and intra-muscular depots) and less muscle, from 85 kg onwards. Although fat levels differed depending on diet regime (LP2>others), proportions of fat in different body depots were unaffected.

Adult muscle size and fibre-type composition are heritable traits that vary substantially between individuals. We used inbred mouse strains in which soleus muscle mass varied by an order of magnitude to explore whether properties of muscle spindles can also be influenced by genetic factors. Skip-serial cross-sections of soleus muscles dissected from 15 male mice of BEH, BEL, C57BL/6J, DUH, LG/J and SM/J strains were analysed for number of muscle spindles and characteristics of intrafusal and extrafusal fibres following ATPase staining. The BEL and DUH strains determined the range of: soleus mean size, a 10-fold difference from 2.1 to 22.3 mg, respectively; the mean number of extrafusal fibres, a 2.5-fold difference from 497 to 1249; and mean fibre-cross-sectional area, three-fold difference, e.g. for type 1 fibres, from 678 to 1948 μm2. The range of mean proportion of type 1 fibres was determined by C57BL/6J (31%) and DUH (64%) strains. The mean number of spindles per muscle ranged between nine (LG/J) and 13 (BEL) (strain effect P < 0.02). Genetic correlations between spindle count and muscle weight or properties of extrafusal fibres were weak and not statistically significant. However, there was a strong correlation between the proportion of spindles with more than one bag2 fibre and the proportion of extrafusal fibres that were of type 1, and strain-dependent variation in the numbers of such spindles was statistically significant. The numbers of intrafusal fibres per spindle ranged from 2 to 8, with the most common complement of four found in 75.6% of spindles. There were no significant differences between the strains in the mean numbers of intrafusal fibres; however, the variance of the number was significantly less for the C57BL/6J strain than for any of the others. We conclude that abundance of muscle spindles and their intrafusal-fibre composition are substantially determined by genetic factors, which are different from those affecting muscle size and properties of the extrafusal fibres.

Meta-analysis was performed to quantify the effects of gender in combination with carcass weight and breed on pork quality. Altogether published results from 43 references were used. The traits analyzed were pH at 45 min (pH45min) and pH at 24 h (pH24hr) postmortem, objective color attributes lightness (L*), redness (a*), and yellowness (b*; CIE color system), color and marbling scores, drip loss, intramuscular fat content (IMF), and backfat thickness (P2), as well as sensory scores of juiciness and tenderness. Data for 2 muscle types, LM and Musculus semimembranosus (SMM), were used for the analysis. Swine genders were defined as intact/entire male (EM), surgically castrated male (SM), immunocastrated male (IM), and entire female (EF). After standardization of scaled traits (color, marbling scores, juiciness, tenderness) and accounting for cold carcass weight (CW), statistical analysis was performed using mixed models where breed was included as random effect. The analysis found a general effect of gender on each trait and multiple comparisons identified significant differences among the individual genders for L* (lightness), marbling scores, IMF, P2 in LM, and pH24hr in SMM. For these traits, when genders were grouped into gender categories as "castrates" (IM, SM) and "natural genders" (EM, EF), significant differences were found among estimates related to these categories. Furthermore, significant differences were found between castrates and individual gender types, indicating that castrated animals statistically segregated regarding their pork quality and regardless of type of castration. Pork of SM/EM animals has been found to be the fattest/leanest and there is indication that IM pork has the lightest meat color. Carcass weight dependence was found to be nonlinear (quadratic) for a*, P2, and marbling scores, and linear for b* and color scores in LM and pH24hr in SMM. The analysis identified significant breed effects for all traits, with large variation in the actual magnitudes (∼10 to 100%) of breed effects among individual traits. The established CW dependencies of pork quality traits in combination with the other influencing factors investigated here provides pork producers with the opportunity to achieve desired pork quality targets for a wide range of CW (∼30 to 150 kg) under standard indoor-rearing conditions.

Implementing the use of spine traits in a commercial breeding program has been seen to improve meat production from the carcass of larger-bodied pigs. The aim of this study was to assess the extent of variation in spine characteristics within and between breeds of sheep and to investigate the association with body length and tissues traits to deliberate if a similar approach could be applicable in the sheep sector. Spine traits (vertebrae number, VN; spine region length, SPL; individual vertebra length, VL) of the thoracic (THOR) lumbar (LUM) and thoracolumbar (T+L) spine regions were measured using x-ray computed tomography (CT) on 254 Texel (TEX), 1100 Scottish Blackface (SBF), 326 Texel cross Mule (TEX × MULE), and 178 Poll Dorset cross Mule (PD × MULE) lambs. Simple descriptive statistics inform that variation in thoracolumbar VN exists within all breeds and crosses; TEX animals showed the largest range of variation in thoracolumbar VN (17 to 21) and the TEX × MULE the smallest (18 to 20). Significant differences were not observed between sexes, but did occur between breeds (P < 0.05), which is indicative of a genetic basis for these traits. Least-squares means identified that TEX had the least thoracolumbar VN (19.24) and SBF possessed the most (19.63); similarly the lowest measures for SPL and VL for each spine region were observed in TEX, but the greatest values for these traits were expressed predominantly in the crosses (TEX × MULE and PD × MULE). Correlation coefficients (r) within each breed or cross support the interpretation of additional vertebrae contributing to a longer length of the spine region in which they occur (P < 0.001; e.g., for PD × MULE lambs), r between traits VNTHOR and SPLTHOR (r = 0.59), VNLUM and SPLLUM (r = 0.94) and VNT+L and SPLT+L (r = 0.65) all reach moderate to very high values. In all breeds and crosses, this relationship is particularly strong for the lumbar region. The few significant (P < 0.05) correlations observed between spine and tissue traits [CT-predicted quantities of carcass fat and muscle (kg) and area of the LM (mm(2))] indicated no substantial relationships, r was small (ranging from -0.25 to 0.19) in each case. To conclude, significant vertebral variation exists within and between sheep breeds and crosses, which can contribute to an increase in body (and carcass) length. Including measurements taken for other primal cuts will further aid in assessing any potential increase in meat production from these longer-bodied sheep.

Oxidative damage caused by reactive oxygen species has been hypothesised to underpin the trade-off between reproduction and somatic maintenance, i.e., the life-history-oxidative stress theory. Previous tests of this hypothesis have proved equivocal, and it has been suggested that the variation in responses may be related to the tissues measured. Here, we measured oxidative damage (protein carbonyls, 8-OHdG) and antioxidant protection (enzymatic antioxidant activity and serum antioxidant capacity) in multiple tissues of reproductive (R) and non-reproductive (N) mice from two mouse strains selectively bred for high (H) or low (L) food intake, which differ in their reproductive performance, i.e., H mice have increased milk energy output (MEO) and wean larger pups. Levels of oxidative damage were unchanged (liver) or reduced (brain and serum) in R versus N mice, and no differences in multiple measures of oxidative protection were found between H and L mice in liver (except for Glutathione Peroxidase), brain or mammary glands. Also, there were no associations between an individual’s energetic investment (e.g., MEO) and most of the oxidative stress measures detected in various tissues. These data are inconsistent with the oxidative stress theory, but were more supportive of, but not completely consistent, with the ‘oxidative shielding’ hypothesis.

Genetic background contributes substantially to individual variability in muscle mass. Muscle hypertrophy in response to resistance training can also vary extensively. However, it is less clear if muscle mass at baseline is predictive of the hypertrophic response. The aim of this study was to examine the effect of genetic background on variability in muscle mass at baseline and in the adaptive response of the mouse fast- and slow-twitch muscles to overload. Males of eight laboratory mouse strains: C57BL/6J (B6, n = 17), BALB/cByJ (n = 7), DBA/2J (D2, n = 12), B6.A-(rs3676616-D10Utsw1)/Kjn (B6.A, n = 9), C57BL/6J-Chr10A/J/NaJ (B6.A10, n = 8), BEH+/+ (n = 11), BEH (n = 12), and DUHi (n = 12), were studied. Compensatory growth of soleus and plantaris muscles was triggered by a 4-week overload induced by synergist unilateral ablation. Muscle weight in the control leg (baseline) varied from 5.2 ± 07 mg soleus and 11.4 ± 1.3 mg plantaris in D2 mice to 18.0 ± 1.7 mg soleus in DUHi and 43.7 ± 2.6 mg plantaris in BEH (p < 0.001 for both muscles). In addition, soleus in the B6.A10 strain was ~40% larger (p < 0.001) compared to the B6. Functional overload increased muscle weight, however, the extent of gain was strain-dependent for both soleus (p < 0.01) and plantaris (p < 0.02) even after accounting for the baseline differences. For the soleus muscle, the BEH strain emerged as the least responsive, with a 1.3-fold increase, compared to a 1.7-fold gain in the most responsive D2 strain, and there was no difference in the gain between the B6.A10 and B6 strains. The BEH strain appeared the least responsive in the gain of plantaris as well, 1.3-fold, compared to ~1.5-fold gain in the remaining strains. We conclude that variation in muscle mass at baseline is not a reliable predictor of that in the overload-induced gain. This suggests that a different set of genes influence variability in muscle mass acquired in the process of normal development, growth, and maintenance, and in the process of adaptive growth of the muscle challenged by overload.

The current EUROP beef carcass classification scheme is still largely dependent on visually assessed fatness and conformation and its purpose is to provide a common basis for the description of carcasses for use in trade, price reporting and intervention. The meat industry, however, aims for accurately predicted saleable meat yield (SMY%) to which the EUROP carcass classification shows highly variable correlations due in part to the variable distribution of fat throughout the carcass as affected by breed, sex, diet, and the level of fat trimming. Video image analysis (VIA) technology is capable of improving the precision and accuracy of SMY% prediction even for specific carcass joints and simultaneously mimics the visual assessment to comply with EU regulations on carcass classification. This review summarises the development and use of VIA for evaluation of beef carcasses and discusses the advantages and shortfalls of the technology and its application.

The Texel Muscling QTL (TM-QTL) is a QTL affecting loin muscling in Texel sheep with a paternal polar overdominant pattern of expression. This study on purebred Texel sheep used the first available data to include homozygote TM-QTL carriers in addition to homozygote non-carriers and both heterozygotes to assess the effect of TM-QTL on live weight throughout growth from birth to slaughter (at around 20 weeks of age) and carcass weight. TM-QTL was found to have an effect on most measures of live and carcass weight. Animals inheriting two copies of TM-QTL showed an increase of 1.5 kg or 9% in carcass weight and an increase in live weight across a range of ages from birth to slaughter of between 7 and 15% compared to animals carrying no copies of TM-QTL. The effect of TM-QTL on the weight traits studied appears to be additive but heterozygote weights did not always support this. If more data on lambs carrying TM-QTL become available in future it would be useful to validate this effect on live and carcass weight and the pattern of the effect.

Genotype by environment interactions (G × E) can form a potential source of inefficiency in animal breeding if selection decisions are made without acknowledging their effects. The presence of such interactions between two Scottish hill farms was investigated using performance data collected from 18,459 Scottish Blackface lambs between 1997 and 2010. Pedigree information was available for 27,548 animals. 30 out of 379 sires used during this time period were used on both farms. Farm A is located on the East Coast of Scotland, whereas Farm B is on the West Coast. The farms differ in a number of aspects including annual rainfall, topography, vegetation, temperature and altitude ranges, with Farm B representing a harsher environment overall. Traits studied were birth weight, 8-week weight and weaning weight, ultrasound back-fat and muscle depths at weaning, carcass weight, carcass fat grade and carcass conformation score. Genetic correlations were estimated for each trait, between the two farms, with those significantly different from 1 ( P s.e. 0.31). By taking G × E into account and comparing bivariate and univariate analyses, the maximum selection response observed for birth weight was 0.0016 kg per generation. Overall, the lack of G × E observed for the majority of traits studied suggest that the common sire offspring have performed similarly across both farms. However, the presence of G × E associated with birth weight may have implications for lambing associated problems, or lamb survival, if sires produce lambs with unexpectedly high or low birth weights.

SummaryUnderstanding how polygenic traits evolve under selection is an unsolved problem [1], because challenges exist for identifying genes underlying a complex trait and understanding how multilocus selection operates in the genome. Here we study polygenic response to selection using artificial selection experiments. Inbred strains from seven independent long-term selection experiments for extreme mouse body weight (“high” lines weigh 42–77 g versus 16–40 g in “control” lines) [2] were genotyped at 527,572 SNPs to identify loci controlling body weight. We identified 67 parallel selected regions (PSRs) where high lines share variants rarely found among the controls. By comparing allele frequencies in one selection experiment [2–4] against its unselected control, we found classical selective sweeps centered on the PSRs. We present evidence supporting two G protein-coupled receptors GPR133 and Prlhr as positional candidates controlling body weight. Artificial selection may mimic natural selection in the wild: compared to control loci, we detected reduced heterozygosity in PSRs in unusually large wild mice on islands. Many PSRs overlap loci associated with human height variation [5], possibly through evolutionary conserved functional pathways. Our data suggest that parallel selection on complex traits may evoke parallel responses at many genes involved in diverse but relevant pathways.

Birth difficulty and poor lamb vigour are significant causes of perinatal lamb mortality. In this study we investigated whether sheep breeds differing in appearance, muscularity and selection history also had differences in dystocia and lamb vigour, and considered some of the factors that may contribute to the variation in these traits. Data were collected at birth from a total of 3252 lambs of two terminal sire breeds selected for lean growth (Suffolk [S], n=500 and Texel [T], n=1207), from a Hill breed (Scottish Blackface [B], n=610), which has been mainly selected for hardiness, and a crossbred (Mule×T [M], n=935) representing a maternal line. For each lamb the degree of assistance at delivery, lamb presentation, amount of assistance to achieve successful sucking, sex, litter size and birth weight were recorded. T lambs required the most, and B and M lambs the least assistance at birth, S lambs were intermediate (% lambs assisted: T=55.7, S=30.7, B=22.7, M=24.9, P

The c.*1232G > A (MM) mutation in the myostatin gene and TM-QTL are two muscle-enhancing polymorphisms found on Chr 2 and Chr 18, respectively, in Texel sheep. Previous studies on purebred lambs and crossbred lambs out of Mule ewes showed that MM was associated with increased muscle mass and decreased fat content whereas heterozygous TM-QTL lambs had increased loin muscle ( M. longissimus lumborum , MLL) depth as measured by ultrasound and increased MLL weight. Welsh Mountain ewes, like Mule ewes, contribute significantly to UK slaughter lamb production from the UK sheep industry's stratified structure. Therefore, this study aimed to evaluate the direct effects of MM and TM-QTL in the genetic background of Texel × Welsh Mountain lambs. Four Texel sires, all MM carriers and two TM-QTL carriers, were used to inseminate Welsh Mountain ewes. Of the 175 lambs born, 130 could be classified for TM-QTL genotype [107 non-carriers (+/+), 23 heterozygous carriers (TM/+)] and 172 for MM genotype [15 non-carriers (+/+), 129 heterozygous carriers (MM/+), 28 homozygous carriers (MM/MM)]. All lambs were weighed at 8 and ∼23 weeks of age and were ultrasound scanned before being slaughtered at ∼24 weeks of age. All carcasses were graded for conformation and fat class, based on Meat and Livestock Commission (MLC) classification scores, and then scanned using a video image analysis (VIA) system to predict weight of carcass primal cuts and trimmed primal cuts, muscularity traits and carcass shape traits. Carrying two copies of MM was associated with a significant positive effect on 8 weeks weight, a negative effect on ultrasound fat depth and a substantial decrease in MLC-fat score. Two copies of MM also had a strong positive impact on VIA-estimated weight of the hind leg, chump and loin primal cuts, as well as the muscularity of the hind leg and loin regions with greater loin muscle width, depth and area. Homozygous MM carrier lambs had significantly wider carcasses across the shoulders, breast and hind legs and greater areas of the back view of the carcass when measured by VIA. Leg and carcass compactness were also significantly associated with the presence of two copies of MM. However, lambs carrying a single copy of MM were not significantly different to non-carriers in any of the traits measured. TM-QTL significantly increased ultrasound muscle depth and TM-QTL carriers had significantly greater loin muscle width and area measurements. Carcass weight did not differ significantly between genotypic classes for MM or TM-QTL. These results agree in general with other reports of the effects of MM and TM-QTL, in both direction and magnitude, on carcass traits.

International audience; Meta-analyses have been carried out to quantify the effect of dietary vitamin E on α-tocopherol accumulation and on lipid oxidation in porcine M. longissimus. Published results of 13 (vitamin E accumulation) and 10 (lipid oxidation) experiments respectively were used for the analyses. After a number of standardization procedures, a nonlinear relationship was found between the supplementary vitamin E and the accumulation of α-tocopherol in pork which approached a maximum value of 6.4 μg/g tissue. Pork lipid oxidation levels were described in terms of Thiobarbituric Acid Reacting Substances (TBARS) values. The statistical analysis revealed significant effect of vitamin E dose, muscle α-tocopherol concentration and supplementation time on TBARS, resulting in two prediction models for lipid oxidation. Meta-analysis has proven to be a valuable tool for combining results from previous studies to quantify the effects of dietary vitamin E. Further studies, carried out with standardized experimental protocols would be beneficial for model validation and to increase the predictive power of the derived models.

This study evaluated the effects of the ovine c.*1232 G > A myostatin mutation (MM) on carcass traits in heterozygous crossbred lambs sired by Texel and Poll Dorset rams using ultrasound, CT scanning, carcass classification and VIA. In experiment 1, MM was associated with increased loin depth (+ 2.8%) and area (+ 3.2%). MM-carriers had significantly higher CT-estimated lean weight and proportion (2 to 4%) and muscle to bone ratio (by ~ 3%), in both experiments, and muscle to fat ratio (28%) in experiment 2. Muscle areas in three cross-sectional CT scans, were higher (2 to 5%) in MM-carriers. In experiment 2, fat-related measurements were significantly lower in MM-carrier lambs but this was not seen in experiment 1. A significant increase in muscle density, indicative of lower intramuscular fat, in MM-carriers shows that meat quality characteristics need attention. Carrying MM significantly decreased carcass fat scores. VIA did not detect any significant MM effects.

Lamb mortality remains a significant welfare and economic issue for sheep production. Lamb survival is to a degree dependent upon an easy delivery and the expression of appropriate behaviours from both mother and offspring, such as rapid standing, udder seeking and sucking by the lamb. Genetic solutions have the potential to improve birth assistance and lamb behaviour but large amounts of data are needed. Therefore, to achieve this objective, simple, proxy methods (scoring systems) were developed to quantify the level of birth difficulties and lamb vigour on farm. In the first study, detailed historical behavioural data from 1156 lambs (Scottish Blackface and Suffolk (S)) were analysed to develop criteria for 3 scores: birth assistance, lamb vigour and sucking assistance. The birth assistance score was developed by analysing the relationships between birth presentation and intervention levels, and intervention level and labour length. Lambs with abnormal birth positions required more assistance than normally presented lambs and lambs with long labours required more and greater assistance than those with short labours. Lamb vigour score was developed by analysing the latencies for the lamb to first perform specific behaviours; more vigorous lambs reach landmark behaviours faster than low vigour lambs. The sucking assistance score was developed from the relationship between the latency to suck successfully and assistance level, where lambs that were slow to suck required more assistance than lambs that were quick to suck. In the second study, the behaviour scoring systems (5-point categorical scales) were validated using a commercial flock of 80 twin-bearing crossbred ewes mated with either Texel (T) or S sires by simultaneously recording scores and the latency to perform specific landmark behaviours (i.e. to stand, seek the udder and suck). The vigour scores (recorded at 5 min of age) were compared with the latency from birth to standing and showed that lambs with lower (better) vigour scores were faster to stand after birth than those with higher scores. The sucking assistance scores were compared with the latency from birth to sucking, and showed that lambs with lower sucking assistance scores are quicker to suck than those with high scores. These results showed that the scoring systems could provide a practical and reliable assessment of birth assistance and lamb behaviour on farm and were sufficiently sensitive to discriminate vigour levels between lambs sired by either S or T rams.

A quantitative trait locus (QTL) has been identified on chromosome 18 in Texel sheep (TM-QTL) that increases depth and area of the longissimus dorsi muscle. The study aimed to assess the pleiotropic QTL effects on key meat quality traits (toughness and intramuscular fat content after >or=7 days aging) of crossbred lambs carrying one copy of the TM-QTL. The results showed that male TexelxMule lambs carrying the TM-QTL had significantly less intramuscular fat (1.86% versus 2.25%) and higher toughness, with increased variation, in the loin muscle, compared to non-carrier males. Similar conclusions were obtained using two different types of tenderometer equipment: one using the Volodkevitch test (average shear force of 4.17 kgF or 40.9N for carrier males, 2.61 kgF or 25.6N for non-carrier males) and one using the MIRINZ test (average shear force of 6.18 kgF or 60.6N for carrier males, 5.22 kgF or 51.2N for non-carrier males). Although most toughness measurements were within published consumer acceptability limits, a few individual TM-QTL carrier lambs had unacceptably tough meat, despite enhanced post-slaughter processing. The TM-QTL did not significantly affect loin toughness in female lambs, leg toughness in either sex, or intramuscular fat content. These results should be considered, alongside direct effects of the TM-QTL on muscling and carcass composition, in recommendations for the use of this QTL by sheep breeders.

Shelly hoof in sheep occurs when the hoof wall becomes detached from the laminar corium; it often then becomes impacted with debris leading to infection, pain and lameness. The problem of shelly hoof is under-reported and is often confused with classical footrot. A study was conducted using data on 9,169 Blackface and Texel sheep from 22 farms in the UK. The aim of the study was to estimate the prevalence of shelly hoof in these breeds, to quantify the genetic basis to shelly hoof, and to describe a pilot trail to characterise the physical properties of horn using Transmission Electron Microscopy (TEM). The results showed that shelly hoof has a high prevalence (47% for Blackface and 24% for Texel ewes) and is under moderate genetic control (h(2) = 0.3). The TEM images showed fragmented dorsal wall horn, microscopic crevices leading deeper into the hoof accompanied by bacteria and other micro-organisms. The invasion of bacteria was facilitated by separation of the cells in a characteristic 'un-zipping' phenomenon, poor attachment of the keratin to the cell membranes, poor cell membrane quality with a 'lace-chain' effect and incomplete keratinisation of the cells.

Bayesian analyses were used to estimate genetic parameters on 5580 records of litter size in the first four parities from 1758 Mule ewes. To examine the appropriateness of fitting repeatability (RM) or multiple trait threshold models (MTM) to litter size of different parities, both models were used to estimate genetic parameters on the observed data and were thereafter compared in a simulation study. Posterior means of the heritabilities of litter size in different parities using a MTM ranged from 0.12 to 0.18 and were higher than the heritability based on the RM (0.08). Posterior means of the genetic correlations between litter sizes of different parities were positive and ranged from 0.24 to 0.71. Data sets were simulated based on the same pedigree structure and genetic parameters of the Mule ewe population obtained from both models. The simulation showed that the relative loss in accuracy and increase in mean squared error (MSE) was substantially higher when using the RM, given that the parameters estimated from the observed data using the opposite model are the true parameters. In contrast, Bayesian information criterion (BIC) selected the RM as most appropriate model given the data because of substantial penalty for the higher number of parameters to be estimated in the MTM model. In conclusion, when the relative change in accuracy and MSE is of main interest for estimation of breeding values of litter size of different parities, the MTM is recommended for the given population. When reduction in risk of using the wrong model is the main aim, the BIC suggest that the RM is the most appropriate model.

Mekkawy, W., Roehe, R., Lewis, R. M., Davies, M. H., Bunger, L., Simm, G., Haresign, W. (2009). Genetic relationship between longevity and objectively or subjectively assessed performance traits in sheep using linear censored models. Journal of Animal Science, 87, (11), 3482-3489. IMPF: 02.47 Sponsorship: DEFRA / Meat and Livestock Commission

Various post-mortem measurements (carcass weights, conformation and fatness classes, external carcass dimensions, eye muscle dimensions, subcutaneous fat depth, pH and temperature) were recorded on 197 Texel (TEX) and 200 Scottish Blackface (SBF) lamb carcasses. The potential use of these measurements to predict carcass composition and key meat quality traits was investigated, to enable categorisation of carcasses in the abattoir and/or for use in genetic improvement programmes. By combining different measurements, accurate predictions of dissected carcass muscle weight (adjusted R(2) 0.93 in TEX, 0.88 in SBF) and fat weight (adjusted R(2) 0.84 in TEX, 0.87 in SBF) were achieved, and moderate predictions of intra-muscular fat (adjusted R(2) 0.56 in TEX, 0.48 in SBF), whilst shear force was predicted with low to moderate accuracy (adjusted R(2)

Texel muscling quantitative trait locus (TM-QTL) is a QTL on chromosome 18, originally identified in purebred UK Texel sheep, which was reported to increase ultrasonically measured muscle depth at the third lumbar vertebra by around 4% to 7%. The objective of the present study was to comprehensively evaluate the TM-QTL and to determine whether it could provide benefits to the UK sheep industry through increased carcass meat yield in crossbred slaughter lambs. Effects of this QTL on a range of carcass traits, including those measured in vivo and by dissection, were evaluated in heterozygous carrier and non-carrier lambs produced by crossing heterozygous carrier Texel rams with non-carrier Mule (Bluetaced Leicester x Scottish Blackface) ewes from a lowland flock. The TM-QTL was found to increase loin muscling in crossbred lambs at a given live weight or carcass weight as measured by ultrasound, X-ray computed tomography (CT) and carcass dissection. Depth of M. longissimus lumborum (MLL) was greater in TM-QTL carrier lambs compared to non-carriers as measured by both ultrasound at the third lumbar vertebra (+43%, P = 0.033) and CT scanning at the fifth lumbar vertebra (+6.7%; P = 0.004). Width and area of MLL measured using CT were also greater in TM-QTL carrier lambs compared to non-carriers (+3.09%; P = 0.013 and + 5.1%; P = 0.047, respectively). Loin muscle volume measured using CT was greater in TM-QTL carriers than in non-carriers (+5.9916; P = 0.005) and the dissected weight of the MLL was + 7.1% greater in TM-QTL carriers compared to non-carriers (P < 0.001). The proportion of the total carcass lean meat yield (LMY) that was contained within the loin region was slightly higher in TM-QTL carriers than in non-carriers (0.154 v. 0.145; P = 0.006). However, TM-QTL was found to have no significant effect on the total weight or proportion of LMY or of saleable meat yield in the carcass measured by dissection, or on muscling in the hind leg measured by CT or dissection. This work has verified that the inheritance of TM-QTL is associated with increased loin muscling in crossbred lambs, as has previously been reported for purebred Texel lambs.

So that genetic studies can be undertaken on footrot in sheep, it is necessary that a reliable and repeatable method to categorise the phenotype is available. This paper summarises the methods used and results obtained from 1600 hoof lesion scores of 100 mixed-age ewes independently scored twice by two trained operators. Using a 5-pont scale describing the severity of foot lesions, residual correlations were used to assess agreement between scorers and scoring occasions. Data were analysed using both zero-1 and continuous data methods. The average prevalence of any score >0 was 15%, and of scores >1 was 12%. The residual correlation between scorers for SUM_FR was 0.87 and between scoring occasions it was also 0.87, indicating high repeatability or agreement both within and between scorers. No significant differences were detected between scorers or between scoring occasions for any of the traits analysed, or different analytical methods used.

Differences in muscularity of the hind leg (HL) and lumbar region (LR) were investigated between sexes (ram vs ewe lambs), breeds (Scottish Blackface, SBF vs Texel, TEX) and progeny of high- and low-muscularity sires (HM, LM) (n=471). The influence of these factors on meat eating quality (MEQ) was also examined (n=229). TEX lambs had 16% greater muscularity than SBF in both regions, whilst differences between sire groups were 4%. Ewe lambs had slightly higher values of muscularity for the HL than rams, but values were similar for the LR. Meat from SBF lambs had higher tenderness, stronger lamb flavour and higher overall liking than TEX meat. Sex had a weak influence with ram lambs having a stronger abnormal flavour and lower overall liking in the LR only. No significant differences in MEQ were found between HM- and LM-sired lambs, suggesting that improvements in muscularity would not have unfavourable effects on MEQ.

We determined whether altered physical activity levels might underlie the contrasting adiposity of a divergently selected polygenic murine model of metabolic syndrome (Fat; F) and leanness (Lean; L) mice. We measured physical activity with a long term running wheel experiment and performed an additional high fat diet intervention. Further, we measured posture allocation by visual monitoring within the home cage as a non-exercise correlate of 'normal' physical activity. Whilst initially similar, running wheel activity of the F line declined with age, while the activity of the L line increased. Food intake was higher in the L line and increased with wheel exposure. Vertical rearing measured by video quantification in the home cage, without the stimulus of a running wheel was also significantly higher in the L line. The two lines developed novel alternate strategies to defend their body weight when exposed to high fat diets with a running wheel. F mice increased their running wheel activity, and despite unaltered food intake, still gained weight. L mice reduced their food intake and maintained activity levels without a significant change in body weight. Phenotypic selection for divergence in body fat content has co-segregated with a genetic predisposition for divergent physical activity levels and different strategies for coping with exposure to high fat diets that will facilitate the discovery of the genes underlying these important obesity related traits.

A multi-trait selection index designed to improve the overall economic performance of hill sheep, inducting both maternal and lamb traits, has been developed and tested in a selection experiment over 7 years. Two versions of the index were tested, with different economic weights applied to the traits, on two different hill farms: one version including maternal and growth traits; the other version with additional breeding goals of carcass weight, fatness and conformation scores. Responses to selection, using both versions of the index, suggest that improvements are being made in overall index score and lamb growth. This study investigated the indirect effects of these selection indices on lamb carcass composition and muscularity traits, as measured using X-ray computed tomography (CT) scanning. A total of 499 lambs from the two hill farms were CT scanned at weaning (approximately 120 days of age). Approximately half of the lambs from each farm were from the selection line (S, animals with highest index scores selected for breeding), while the other half were from a control line (C, animals with average index scores selected). Composition and muscularity traits were estimated on each lamb from CT data and differences between genetic lines investigated within farm, using restricted maximum likelihood analyses, adjusting for either live weight or age. Results showed that the selection index without carcass traits produced lambs with carcass composition that was not significantly different to control lambs at a given live weight or age. Including carcass traits in the index resulted in lambs with no compositional differences (except for a slight increase in bone) at a set age compared with controls. At a given live weight however, selection lambs had less fat and lower carcass weights and killing-out percentage. Muscularity (3-D muscle shape) and muscle area shape (2-D) were not improved as a result of selection on either version of the index (including carcass weight and grades in the breeding goals or not) and, at a fixed live weight, muscularity in hind leg and lumbar regions tended to be higher in the C line. To accelerate changes in carcass composition and muscularity within the context of a multi-trait selection index for hill sheep, consideration should therefore be given to including objective CT-derived carcass traits in the index in addition to the Meat and Livestock Commission (MLC) carcass grades or ultrasound measurements.

Objective: Obesity is thought to result from an interaction between genotype and environment. Excessive adiposity is associated with a number of important comorbidities; however, the risk of obesity-related disease varies with the distribution of fat throughout the body. The aim of this study was to map quantitative trait loci (QTLs) associated with regional fat depots in mouse lines divergently selected for food intake corrected for body mass. Research Methods and Procedures: Using an F2 intercross design (n = 457), the dry mass of regional white (subcutaneous, gonadal, retroperitoneal, and mesenteric) adipose tissue (WAT) and brown adipose tissue (BAT) depots were analyzed to map QTLs. Results: The total variance explained by the mapped QTL varied between 12% and 39% for BAT and gonadal fat depots, respectively. Using the genome-wide significance threshold, nine QTLs were associated with multiple fat depots. Chromosomes 4 and 19 were associated with WAT and BAT and chromosome 9 with WAT depots. Significant sex × QTL interactions were identified for gonadal fat on chromosomes 9, 16, and 19. The pattern of QTLs identified for the regional deposits showed the most similarity between retroperitoneal and gonadal fat, whereas BAT showed the least similarity to the WAT depots. Analysis of total fat mass explained in excess of 40% of total variance. Discussion: There was limited concordance between the QTLs mapped in our study and those reported previously. This is likely to reflect the unique nature of the mouse lines used. Results provide an insight into the genetic basis of regional fat distribution.

Assessments of muscle mass and skeletal dimensions by Computed Tomography (CT) enable the development of new muscularity indices for the hind leg (HL) and lumbar region (LR) in lambs. Compared to previous CT muscularity indices, the accuracy was much higher with the new index in the HL (correlations between CT and dissection indices of 0.89 vs 0.51). The accurate measurement of femur length by CT used in the calculation of the new HL index made an important contribution to the higher accuracy of the index. The improvement in accuracy was smaller for the LR (0.55 vs 0.44). The association of CT muscularity indices and carcass quality in Texel and Scottish Blackface lambs showed that improved muscularity is not phenotypically correlated with detrimental effects on carcass composition. CT muscularity indices provide an alternative method to improve carcass conformation and leanness, using measurements that at a constant weight are independent of fatness.

The objective of this study was to investigate and estimate the associations of the ovine prion protein (PrP) genotypes with a wide range of performance traits in Scottish Blackface lambs. Performance records of up to 7,138 sheep of known PrP genotypes born from 1999 to 2004 in 2 experimental farms were utilized. Performance traits studied were BW at birth, marking (when the sheep were identified with permanent ear tags at an average age of 52 d), and weaning (average age of 107 d); slaughter traits (BW at slaughter, slaughter age, carcass weight, and carcass conformation); ultrasonic muscle and fat depths; and computerized tomography-predicted carcass composition and carcass yield at weaning. Different linear mixed models, including random, direct animal effect, and up to 3 maternal effects (genetic, permanent, and temporary environmental) were used for the different traits. The PrP genotype was included in the model as a fixed effect, along with other fixed factors with significant effects (P < 0.05). Five separate analyses were carried out for each trait, differing in the method of PrP genotypic classification. The first analysis was based on classifying the sheep into categories according to all 9 available PrP genotypes. In the other 4 analyses, sheep were categorized according to the number of each PrP allele carried. Results showed that there were no significant differences between PrP genotypes for any of the performance traits studied when all 9 genotypes were compared (first analysis). Similarly, performance of the lambs did not significantly differ between genotypes with different numbers of ARR copies. However, there were significant variations in a few traits with respect to the number of ARQ, AHQ, and VRQ alleles carried. Heterozygous lambs for the AHQ or the ARQ allele were significantly heavier at some ages than lambs of the other genotypes. Lambs carrying the VRQ allele required approximately 10 d longer finishing time (P = 0.01) and yielded carcasses approximately 0.5 kg heavier (P = 0.03) compared with noncarriers. The few significant associations found do not have a negative influence on performance when selecting against the most susceptible PrP allele (VRQ) or in favor of the most resistant one (ARR). Overall, there were no major associations of PrP genotypes with most lamb performance traits in Scottish Blackface sheep.

Male and female Texel (Tex, n = 130) and Scottish Blackface (SBF, n = 103) lambs were grazed together on low-ground pastures from birth to slaughter. Lambs were scanned using computer tomography (CT) on a maximum of four occasions during the growth period: at approximately 8, 11 and 16 weeks of age and pre-slaughter, which occurred in five batches over a 12-week period. The aim was to investigate the use of in vivo CT scanning over the growth period (from ca. 15 to 45 kg live weight, corresponding to an age of ca. 40 to 200d) to study changes in carcass traits and their relationships during growth, in two contrasting breeds. Relationships among CT traits and between CT traits and live weight were investigated within breed, to assess changes with growth. Increased live weight was associated with increases in total fat proportion, fat:muscle ratio, muscle:bone ratio, loin muscle area and proportion of fat in the chest region, in both breeds. Two-dimensional muscle shape (depth:width ratio) in the hind leg (HL S ) and the loin (LM S ), and proportion of muscle in the loin also increased with live weight in Tex lambs. Live weight was negatively associated with proportion of fat in the leg in both breeds, and with HL S , LM S and CT fat density in SBF lambs. Similar trends between CT traits and total fat proportion suggest that associations hold for increasing maturity, as well as size. The results suggest that slaughtering SBF lambs at lighter weights will avoid them becoming over-fat, maintain overall muscle proportion at a higher level and lead to rounder muscle shapes in the hind leg and loin. However, Tex lambs can be slaughtered at heavier weights without becoming over-fat, and this will result in a higher proportion of muscle being deposited in the economically important loin area, and the muscles in the loin and hind leg being rounder in cross-section. CT scanning lambs during growth allows accurate composition and muscle shape measurements on large numbers of lambs at different stages of development and can help understand the developmental patterns of different economically important sheep breeds. This knowledge can aid in management decisions to improve carcass quality at slaughter. Further work is now needed to examine the genetic background to the relationships between traits presented in this study, and their changes with growth, to allow the incorporation of such CT traits into selection programmes for different sheep breeds.

International audience; AbstractBackgroundThis is the first study based on a genome-wide association approach that investigates the links between ovine footrot scores and molecular polymorphisms in Texel sheep using the ovine 50 K SNP array (42 883 SNPs (single nucleotide polymorphisms) after quality control). Our aim was to identify molecular predictors of footrot resistance.MethodsThis study used data from animals selected from a footrot-phenotyped Texel sheep population of 2229 sheep with an average of 1.60 scoring records per animal. From these, a subset of 336 animals with extreme trait values for footrot was selected for genotyping based on their phenotypic records. De-regressed estimated breeding values (EBV) for footrot were used as pseudo-phenotypes in the genome-wide association analysis.ResultsSeven SNPs were significant on a chromosome-wise level but the association analysis did not reveal any genome-wise significant SNPs associated with footrot. Based on the current state of knowledge of the ovine genome, it is difficult to clearly link the function of the genes that contain these significant SNPs with a potential role in resistance/susceptibility to footrot. Linkage disequilibrium (LD) was analysed as one of the factors that influence the power of detecting QTL (quantitative trait loci). A mean LD of 0.20 (r2 at a distance of 50 kb between two SNPs) in the population analysed was estimated. LD declined from 0.15 to 0.07 and to 0.04 at distances between two SNPs of 100, 1000 and 2000 kb, respectively.ConclusionsBased on a relatively small number of genotyped animals, this study is a first step to search for genomic regions that are involved in resistance to footrot using the ovine 50 K SNP array. Seven SNPs were found to be significant on a chromosome-wise level. No major genome-wise significant QTL were identified.

This study compared the use of various models to describe growth in lambs of 2 contrasting breeds from birth to slaughter. Live BW records (n = 7559) from 240 Texel and 231 Scottish Blackface (SBF) lambs weighed at 2-wk intervals were modeled. Biologically relevant variables were estimated for each lamb from modified versions of the logistic, Gompertz, Richards, and exponential models, and from linear regression. In both breeds, all nonlinear models fitted the data well, with an average coefficient of determination (R 2 ) of >0.98. The linear model had a lower average R 2 than any of the nonlinear models ( 0.92). Selection on growth variables seems promising (in Texel more than SBF), but high genetic correlations between variables may restrict the possibilities to change the growth curve shape. A random regression model was also fitted to the data to allow predictions of growth rates at relevant time points. Heritabilities for growth rates differed markedly at various stages of growth and between the 2 breeds (Texel: 0.14 to 0.74; SBF: 0.07 to 0.34), with negative correlations between growth rate at 60 d of age and growth rate at finishing. Following these results, future studies should investigate genetic relationships between relevant growth curve variables and other important production traits, such as carcass composition and meat quality.

A unique set of seven mouse lines, long-term selected for high growth, from different laboratories around the world has been comprehensively compared to evaluate these resources for future QTL and gene mapping for growth traits. The heaviest line (DUH) was 40% (males) to 44% (females) heavier than the smallest line (ROH) at birth, and 105% (males) to 114% (females) heavier at 98 d. Body conformation (body length and width, body areas), body composition (dry matter, fat, fatty acid composition, organ weights), and skeletal muscle cellularity also differed substantially. DUH was more than 20% longer (12.3 cm) compared to the shortest line ROH (9.7 cm). DAH (22.5%) had the highest percentage of gonadal fat and the leanest was BEH (7.7%). Line BEH (0.49 g) showed the highest weight for the left M. rectus femoris, which was 2.1 times higher, compared to ROH (0.23 g). These results suggest that different alleles, and possibly different physiological pathways, have contributed to the selection response in the different lines. Therefore these selection lines are an important tool with which to identify the genetic and physiological basis of growth as they may contain many, if not all, growth promoting alleles.

Two selection indexes, one intended for lamb producers and finishers and one for store lamb producers, were derived using genetic parameters for carcass and maternal characteristics from Conington et al. (2001) and economic values from Conington et al. (2004). This paper summarizes responses to selection for lamb traits only, after 5 years of selection (1998 to 2003) on two farms using these selection indexes. The index for lamb producers and finishers, evaluated on farm 1, with a flock size of 680 ewes, includes economic weightings for maternal traits as well as carcass weight, fat and conformation grades, whereas the index for store lamb producers, evaluated on farm 2, with a flock size of 580 ewes, only includes economic values for maternal traits and lamb growth to weaning. Three selection lines of Scottish Blackface sheep per farm were created with the first lambs born to each line in 1999. These lines were selection (S), control (C) and industry (I); they were of equal size on each farm. Five top- and five average-performing ram lambs were selected each year for the S and C lines respectively using a multi-trait best linear unbiased prediction (BLUP) implementation of the indexes. The I-line used four mature rams bought from industry, selected on appearance only, i.e. adherence to breed ‘type’. Results showed that 5 years after the implementation of the index, the S line had significantly higher index scores than the C or I lines on both farms. The means (s.d.) for the average index scores in 2003 are 114 (328), 119 (371) and 451 (328) (farm 1), and −8 (146), −11 (130), and 250 (129) (farm 2) for the C, I and S lines, respectively, giving predicted net differences (S-C) of £3·38 (farm 1) and £2·58 (farm 2) per ewe. Phenotypic responses showed significant S v. C differences in weaning weight on both farms. As predicted from previous analyses, no changes in carcass quality traits were seen at farm 1 although S-line carcass weights tended to be heavier than those from the C or I lines. The results show that genetic improvement using multi-trait selection indices has been successful and it is a viable, long-term strategy to improve levels of production for hill sheep in extensive environments.