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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.

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.

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.

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.

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.

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.

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.

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.

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.

Transgenic and knockout models have been used successfully in order to attribute specific functions to distinct growth factors. However, it is not clear which from the different IGF-components are actually altered when growth is affected. Furthermore it is not clear if unique or redundant patterns of IGF-component expression are present under conditions of elevated or reduced growth. To address these questions we have used a unique set of mouse models generated by divergent selection for high and low body growth. The set of mouse models consisted of eight mouse lines established in different laboratories. We have studied systemic and local expression of growth relevant genes in these mouse lines highly diverging for body and carcass weights but also for nose-rump lengths. As a strictly conserved pattern, serum IGF-I levels were dramatically increased in all H-lines if compared with the respective L-lines. By contrast serum IGFBP concentrations did not reveal clear patterns of expression in response to growth selection: IGFBP-3 was elevated in some H-lines, IGFBP-2 was increased in H- or L-lines and IGFBP-4 was similar in H- and L-lines. The fact that IGFBP-2 was the only IGFBP elevated in part of the L-lines, identifies IGFBP-2 as an exclusive although facultative negative effector for growth in the circulation among all other IGFBPs. In muscle tissue from selected breeding groups characterized by specific increases of the carcass weights we found redundant patterns of gene expression indicating the absence of tissue-specific or uniquely fixed expression patterns during growth selection within muscle tissue. The finding that serum but not tissue IGF-I levels were strictly positively correlated with growth during growth selection argues for an important role of endocrine IGF-I for postnatal growth in mice.

Summary The growth of males sampled from two mouse lines long-term selected for over 86 generations on body weight (DU6) or on protein amount (DU6P) was analysed from birth till 120 days of age and compared to the growth of an unselected control line (DUKs). Animals from the selected lines are already approximately 40 to 50% heavier at birth than the controls. This divergence increases to about 210 to 240% at the 120 day of age. With birth weights of 2.2 and 2.4 g and weights of 78 and 89 g at the 120 day these selection lines are the heaviest known mouse lines. The fit of three modified non-linear growth functions ( Gompertz function, Logistic function, Richards function) was compared and the effect of three different data inputs elucidated. The modification was undertaken to use parameters having a direct biological meaning, for example: A: theoretical final body weight, B: maximum weight gain, C: age at maximum weight gain, D (only Richards function): determines the position of the inflection point in relation to the final weight. All three models fit the observed data very well (r 2 = 0.949–0.998), with a slight advantage for the Richards function. There were no substantial effects of the data input (averages, single values, fitting a curve for every animal with subsequent averaging the parameters). The high growth of the selected mice is connected with very substantial changes in the final weight and in the maximum weight gain, whereas the changes of the age at the point of inflection were, although partially significant, relatively small and dependent on the model used.

N. Clelland ⁎, L. Bunger , K.A. McLean , J. Conington , C. Maltin , S. Knott , N.R. Lambe a a Animal Breeding and Genetics, Animal and Veterinary Sciences Group, Scotland's Rural College, (SRUC), West Mains Road, Edinburgh EH9 3JG, United Kingdom b Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, West Mains Road, Edinburgh EH9 3JT, United Kingdom c Quality Meat Scotland (QMS), Rural Centre, West Mains Road, Ingliston, Newbridge EH28 8NZ, United Kingdom Meat Science 104 (2015) 92

1 page, 1 table.-- Contributed to: Proceedings of the British Society of Animal Science (Belfast, UK, 12-14 April, 2010)., [EN] Weight, proportion and distribution of fat and muscle in beef carcasses are of importance in order to maximise economic value and reduce waste. In-vivo ultrasound-measured predictors of cattle carcass composition could be of use when taken at the beginning of the finishing period (to allocate feeding groups and levels or for early selection of potential breeding stock), or pre-slaughter (to market-select finished animals, sort carcasses on quality, or feed back information from slaughter animals to breeding programmes). The aims of this study were to investigate the ability of ultrasound-measured fat and muscle depths to predict carcass composition and tissue distribution and to quantify the relative accuracy of predictions using ultrasound measurement taken at the start or end of the finishing period., SAC receives funding from the Scottish Government.

Matheson, S. M., Roden, J., Haresign, W., Bunger, L., Dwyer, C. M. (2010). Selection of sires with good lambing and lamb vigour characteristics within three Suffolk strains. Advances in Animal Biosciences, p170. Proceedings of the British Society of Animal Science Annual Conference, 'Food, Feed, Energy and Fibre from Land - A Vision for 2020', Queen's University, Belfast, Northern Ireland, 12-14 April 2010.