The study was undertaken in a Creole goat flock at INRA-Gardel in Guadeloupe, to evaluate the opportunity to use artificial selection as a means of controlling gastro-intestinal infection during early lactation. The flock grazed all year on Digitaria decumbens pastures. Faecal and blood samples were taken from kids at 11 months of age and from does at kidding before drenching (week 0) and at weeks 4 and 6 after kidding. Faecal egg counts (FEC) were estimated using a modified McMaster method. Blood samples were used to determine packed cell volume (PCV) and eosinophil concentrations (EOS) values. Haemonchus contortus, Trichostrongylus colubriformis and Oesophagostomum columbianum were the main strongyle species identified in faecal cultures. The data came from 1092 litters obtained from 688 does sired by 142 bucks and 413 dams. Variance and covariance components for genetic and residual effects were estimated with multivariate animal models using the restricted maximum likelihood VCE package. Repeatability and overall heritability for FEC during the post-partum period were 0·17 and 0·10±0·02. The genetic correlations between FEC and PCV were −0·56±0·11 at 4 weeks after kidding and −0·79±0·13 at 6 weeks after kidding. The genetic correlations between FEC and EOS were 0·37±0·15 at 4 weeks after kidding and 0·68±0·17 at 6 weeks after kidding. Hence, does that contributed least to pasture contamination during the postpartum period also had low EOS and high PCV breeding values. The genetic correlations between FEC measured at 11 months of age and FEC during periparturient period ranged from 0·57±0·12 to 0·76±0·16. Therefore, breeding goats for increased resistance during the post-weaning period will lead to a less marked and less persistent rise in doe FEC during early lactation. The epidemiological implications of this selection have to be quantified in terms of lower pasture contamination, lower kid parasitism, and higher milk production of does.

Trends in milk production, calving rates, and survival were monitored on a potential 5580 primiparous and multiparous Holstein-Friesian dairy cows across 14 Irish seasonal spring-calving dairy farms between the years 1990 and 2001. Over this period calving rate to first service (CALV1) reduced by 0·96% per year (55 to 44%; P< 0·001), calving rate to first and second service (CALV12) reduced by 0·84% per year ( 77 to 70%; P< 0·001) and herd average parity number reduced by 0·10 lactation per year (4·3 to 3·5; P<0·001). The proportion of North American Holstein Friesian (NAHF) genes in the cows increased by 5·5% per year (8 to 63%; P<0·001), while pedigree index for milk yield (PIMILK) of the cows increased by 25 kg per year ( P<0·001). The predicted difference of the sires of the cows for calving interval and survival increased by 0·5 days (P<0·001) and reduced by 0·12% ( P<0·001) per year, respectively. A negative association was found between increased phenotypic milk yield, NAHF and PIMILK and reduced calving rates as assessed by CALV1 and CALV12. Increased proportion of NAHF genes exhibited a negative effect on survival ( P<0·001) whereas increased levels of heterosis had a positive impact on survival ( P<0·001). The results of the present study indicate that in seasonal calving herds in Ireland a need for direct selection on traits related to fertility and survival is required to arrest and reverse the declining trends in calving rates and survival.

Animals living in temperate climates are continually adapting to seasonal demands of reproduction and survival. Whilst it is well documented that ruminants show seasonal changes in both reproductive and non-reproductive physiological and behavioural characteristics (reduction of metabolic rate and appetite during the winter with respective increases during spring and summer), this information has not been fully established in the non-ruminating ungulate species of Equidae. This may be important information from a practical management perspective since groups of equids are increasingly being kept in natural conditions for the purposes of conservation grazing.

The aim of this study, therefore, was to document the behavioural and physiological adaptive changes made by ponies during a 12-month period and to relate these to changes in forage availability and environment. Five mature pony stallions were kept in west Wales (4°5′W, 52°25′N) and monitored for 12 months. A range of physiological (testis size, body weight, condition score (CS), hoof growth, moult (M), pelage fibre length, depth and density) and behavioural measurements (foraging and non-foraging activities) were recorded along with monthly forage analysis (crude protein (CP), water-soluble carbohydrates (WSC)), dry matter (DM)) and environmental conditions (day length and minimum ambient temperature). All physiological measurements were significantly (P<0·001 to P<0·05, r2=0·16 to 0·69) related to day length and all except testis size, body weight and M were significantly related to minimum temperature, CS (P<0·001; r2=0·583), hoof growth (P<0·001; r2=0·457), pelage fibre length (P<0·001; r2=0·61), pelage fibre depth (P<0·001; r2=0·489) and pelage density (P<0·05; r2=0·192). Fewer significant relationships were observed in relation to forage characteristics; significances only obtained between CP and CS (P<0·001; r2=0·854), fibre length (P<0·01; r2=0·625) and pelage fibre depth (P<0·01; r2=0·624); between DM and CS (P<0·05; r2=0·352) and pelage fibre depth (P<0·05; r2=0·343); between WSC and pelage fibre depth (P<0·01; r2=0·55) and pelage fibre depth (P<0·05; r2=0·34). Behaviour results showed a significant relationship between time spent alert and day-length (P<0·05; r2=0·35) and between minimum ambient temperature and time spent eating (P<0·05; r2=0·37), locomotory behaviour (P<0·01; r2=0·53) and passive interaction (P=0·001; r2=0·63). A significant relationship was also reported between eating and CP (P<0·01; r2=0·53) as well as DM (P=0·01; r2=0·43). The ponies in this study demonstrated a series of adaptive changes during winter concomitant with energy conservation, however, forage availability and intake also decreased indicating lower energy input. Despite energy conserving adaptations it is unlikely that nutrient intake was adequate to account for the limited winter decline in CS and weight. In conclusion, it was considered that: (a) ponies demonstrated physiological and behavioural adaptation in response to environmental demands, (b) during winter ponies demonstrated behaviours indicative of a cost benefit analysis of expending energy in the pursuit of poor quality forage, (c) despite energy conserving adaptations, intake is unlikely to have been adequate to maintain the CS observed, and (d) reduction in metabolic rate and increased food conversion efficiency may be additional adaptations made during times of environmental challenge.

Estimates of co(variance) components were obtained for weights at birth, weaning and 6, 9 and 12 months of age in Muzaffarnagari sheep maintained at the Central Institute for Research on Goats, Makhdoom, Mathura, India, over a period of 28 years (1976 to 2003). Records of 5530 lambs out of 169 rams and 1631 ewes were used for the study. Analyses were carried out by restricted maximum likelihood (REML), fitting six animal models, including various combinations of maternal effects. Heritability estimates for weight at birth, weaning and 6, 9 and 12 months of age were 0·09, 0·21, 0·06, 0·10 and 0·14, respectively. Maternal heritability of body weight declined from 0·07 at birth to 0·02 at weaning. The maternal permanent environmental component contributed 10 to 11% to the total variance for all traits except weight at 12 months. A significant large negative genetic correlation was observed between direct and maternal genetic effects on weaning weight, suggesting the presence of antagonistic environmental, as well as perhaps genetic, effects in daughter and dam. Results suggest that maternal additive effects were only important in early stages of growth, whereas a permanent environmental maternal effect existed at all ages up to 9 months, probably as a carry-over effect of maternal influences present at weaning. Modest rates of genetic progress appear possible for all weights, but the presence of an antagonism between direct and maternal effects on weaning weight would complicate attempts to improve both by selection.

Five musk deer species (genus Moschus) are distributed in China, and the present estimated numbers in the wild are between 220 000 and 320 000. Population size of musk deer has dropped significantly due to historical over-hunting and loss or degradation of their habitat. Musk deer farming, therefore, has become one of the most appropriate ways to protect and utilize musk deer resources. In China, musk deer farming and extracting musk from the captive musk deer have been reasonably successful since the early 1950s. At present three species of musk deer, namely forest (Moschus Berezovskii), alpine (M. sifanicus) and Siberian (M. moschiferus) musk deer are farmed in China and, of these, the forest musk deer is the main captive population. The present patterns of musk deer farming in China, however, need to be improved and developed into more economic and scientific modes in order to improve the rate of survival and reproduction, and to increase the production of musk.

The objective of this study was to examine genetic changes in reproduction traits in sows (total number born (TNB), number born alive (NBA), average piglet birth weight (ABW) and number of piglets weaned (NW), body weight prior to mating (MW), gestation length (GL) and daily food intake during lactation (DFI)) in lines of Large White pigs divergently selected over 4 years for high and low post-weaning growth rate on a restricted ration. Heritabilities and repeatabilities of the reproduction traits were also determined. The analyses were carried out on 913 litter records using average information-restricted maximum likelihood method applied to single trait animal models. Estimates of heritability for most traits were small, except for ABW (0·33) and MW (0·35). Estimates of repeatability were slightly higher than those of heritability for TNB, NBA and NW, but they were almost identical for ABW, MW, GL and DFI. After 4 years of selection, the high growth line sows had significantly heavier body weight prior to mating and produced significantly more piglets born alive with heavier average birth weight than the low line sows. There were, however, no statistical differences between the selected lines in TNB or NW. The lower food intake of high relative to low line sows during lactation was not significant, indicating that daily food intake differences found between grower pigs in the high and low lines (2·71 v. 2·76 kg/day, s.e.d. 0·024) on ad libitum feeding were not fully expressed in lactating sows. It is concluded that selection for growth rate on the restricted ration resulted in beneficial effects on important measures of reproductive performance of thea sows.

The best means to utilize X-ray computed tomography (CT) and ultrasound to predict carcass lean, fat and bone weights in vivo in terminal sire sheep were tested. Data on 160 lambs from three breeds were considered: 50 Suffolk males, 50 Suffolk females, 40 Texel males and 20 Charollais males. One-fifth of the lambs within each breed and sex group were slaughtered at each of 14, 18 and 22 weeks of age and the remaining two-fifths at 26 weeks. Carcasses were dissected into lean, fat and bone weights. Prior to slaughter all lambs were CT scanned, with cross-sectional scans taken at seven sites along the body (ischium, hip, mid shaft of femur, 2nd and 5th lumbar vertebrae and 6th and 8th thoracic vertebrae), and ultrasound scanned at the 3rd lumbar vertebra and 13th rib.A set of three CT scans that reliably predicted carcass lean, fat and bone weights was identified which included a scan in each of the three main carcass regions: ischium in the hind leg, 5th lumbar vertebra in the loin and 8th thoracic vertebra in the shoulder. Breed and sex affected the intercepts of the prediction equations but not their slopes. Therefore, a minimal set of equations is likely to be sufficient to predict tissue weights, at least within terminal sire sheep breeds. Equations derived showed high degrees of fit to the data with R2 values of 0·924, 0·978 and 0·830 for lean, fat and bone weights, respectively, when predicted using CT alone, and 0·589 and 0·857 for lean and fat weights, respectively, when predicted using ultrasound alone. Using live weight in addition to CT information only improved prediction accuracy slightly for lean (0·966) and fat (0·986) although more substantially for bone (0·925). Where live and tissue weights are considered contemporaneously in genetic evaluations, excluding live weight from prediction may therefore be preferable to avoid colinearity among weight measures.

Transport and accompanying mixing of pigs causes fights among pigs and stress resulting in decreased welfare and reduced meat quality. This study investigates the effect of toys available during transport and lairage on behaviour, stress responses, and meat quality of slaughter pigs. Cross-bred (Piétrain×Hypor) pigs (109·1±10·1 kg) were allocated to one of three treatments during transport and lairage: 1) no toys (control) 2) rubber toys and 3) balls. The rubber toy consisted of two fixed rubber sticks; the plastic ball was filled with pieces of maize, which became available for the pigs in small amounts by manipulating the ball. Per group of 11 pigs, two toys were provided. Totally, divided over 4 replicates, 144 pigs were involved, of which 72 were used for blood sampling and meat quality measurements. Five minutes scans during lairage revealed that treatment did not affect the percentage of pigs that lay (P=0·20), stood (P=0·83) or sat (P=0·12) and that in almost all scans at least one pigs was manipulating a ball, compared with half of the scans in which at least one animal was manipulating a rubber toy (P=0·02). However both toys resulted in a lower incidence of shoulder lesions compared with the control group (P=0·06; 31·1% and 28·9% of the pigs for the rubber toys and balls respectively, versus 51·1% for the control group). Blood sampling at sticking showed that pigs with the balls during transport and lairage tended to have lower cortisol concentrations (P=0·07) than pigs with the rubber toys. Also, a decrease in plasma lactate concentration was observed for these pigs in comparison with the control group (P=0·08), and a higher pH of the m. longissimus dorsi 45 min post mortem for the pigs with the balls was found than for the pigs with the rubber toys (P=0·01). These results indicate that enrichment of compartments during transport and lairage with balls reduced glycolysis in muscle resulting in a lower lactate production and a slower pH decline. The pH 45 min post mortem of the m. biceps femoris and the pH, electrical conductivity, colour, and water-holding capacity of the loin 48 h post mortem were not affected by treatment. In conclusion, environmental enrichment with toys during transport and lairage can decrease shoulder lesions and lower the pH decline 45 min post mortem, especially by provision of plastic balls filled with maize.

The objective of this study was to investigate the effects of strain of Holstein-Friesian cow, pasture-based feeding system (FS) and their interaction on milk production, dry matter (DM) intake and energy balance over 3 years consecutively. The three strains were: high milk production North American (HP), high fertility and survival (durability) North American (HD) and New Zealand (NZ). The FS were: a high grass allowance (HG FS), a high concentrate (HC FS) and a high stocking rate (HS FS). A separate farmlet existed for each FS and a total of 99, 117 and 117 animals were used in year 1, year 2 and year 3, respectively, divided equally between strains and FS. Individual animal intakes were estimated three times each year at pasture; in May (P1), in July (P2) and October (P3), corresponding on average to day 102, 177 and 240 of lactation, respectively. The HP cows achieved the highest milk yield, the NZ the lowest, while the HD was intermediate; the HP achieved the highest solid corrected milk yield with no difference between the NZ and HD strains. The grass DM intake of the HP strain was highest ( P<0·001) in all feeding systems. There was a significant strain×FS interaction for yield of milk, fat and protein, grass DM and total DM intake. The milk production response to the HC FS in P1 and P2 was significantly greater for both the HP and HD strains than for the NZ strain, while in P3 the response was highest for the HP, lowest for the NZ and intermediate for the HD. The reduction in pasture DM intake per kg of concentrate was greatest for the NZ strain, lowest for the HP and intermediate for the HD strain. The NZ strain also had the highest grass DM intake per kg live weight. The existence of strain×FS interactions for production and DM intake indicate that greater knowledge of both genotype and feeding environment is required to predict animal performance.

Sheep farming in the UK is characterized by a crossbreeding system where ‘Longwool’ sire breeds are mated with hill dam breeds, with the crossbred (F1) ewe lambs retained for mating to terminal sires. The F1 wether and terminal-sire cross lambs are marketed for meat. At selection, F1 females are typically assessed visually for type traits relevant to dam lines, and these traits could be considered as goal traits. Their offspring and their male sibs derive their value from carcass traits. This study investigated the genetic relationships between type (subjective) and carcass (objective) traits in F1 lambs, and their potential impact on genetic improvement within this production system. Bluefaced Leicester rams were crossed with Scottish Blackface and Hardy Speckled Face ewes to produce F1 (‘Mule’) lambs. The wether lambs (no.=2197) were selected for slaughter at a target condition (a carcass fat score of 2/3L) and a number of live and carcass traits were measured. Carcass dissection data were collected on approximately one-third of these wether lambs. The ewe lambs (no.=2423) were measured for similar live traits but at a fixed age (195±5·5 days). In addition, they were subjectively assessed for a number of functional and type traits. Genetic parameters among these traits were then estimated. Heritabilities for the ewe traits were generally moderate (0·18 to 0·31) and genetic correlations between the traits were variable, with some moderate to high correlations (favourable in direction) of growth/carcass traits with overall type traits. Live weight at slaughter in wethers was highly correlated to live weight at constant age in ewes (r=0·72). In the wethers, live, cold carcass and lean weight had moderately high heritabilities (between 0·26 and 0·46), and were positively correlated with slaughter age (≥0·79). However, age at slaughter in wethers was highly negatively correlated with growth/carcass and overall type traits in ewes (between −0·45 and −0·97), perhaps reflecting differences in maturity in lambs measured at a target fatness versus age. The correlations of most other type traits in ewes with wether traits were non-significant. These results show that the subjectively assessed type traits (at least as measured in this study) will not deteriorate, and some will in fact be improved, in a selection programme aiming to improve carcass merit.

It was reasoned that, if we used a large sample of pigs, we could demonstrate that total and differential numbers of leukocytes, expression levels of swine leukocyte antigens (SLA) I and II, and serum concentrations of IgG and haptoglobin show additive genetic variation and are, therefore, potentially useful as criteria to improve selection of pigs for resistance to clinical and subclinical disease. We tested this premise by assessing 4204 male pigs from the Duroc, Landrace, and Yorkshire breeds for total and differential numbers of leukocytes and serum concentrations of IgG and haptoglobin; 1217 of the Duroc and Landrace pigs were also assessed for expression levels of SLA I and II. We estimated the amount of additive genetic variation by fitting linear animal models to the total and differential numbers of leukocytes and serum concentrations of IgG and haptoglobin. We fitted linear sire models to the expression levels of SLA I and II. We detected additive genetic variation for each group of traits. Total and differential numbers of leukocytes were moderately heritable (h2=0·22 to 0·30), expression levels of SLA I and II were moderate-to-highly heritable (h2=0·46 to 1·23), while serum concentrations of IgG and haptoglobin were lowly heritable (h2=0·14 to 0·16). The additive genetic variation shown for the immunological traits is encouraging for pig breeders. It indicates that these traits are potentially useful as criteria to improve selection of pigs for resistance to clinical and subclinical disease.

Where wildlife act as a reservoir of disease for domestic mammals, measures solely based on management of either in isolation are unlikely to resolve the problem. Many such diseases can have serious economic implications for farmers and the economy and their management can present considerable challenges. Traditionally, wildlife populations have been culled in attempts to reduce the risks of disease transmission to livestock (e.g. bovine tuberculosis in European badgers and brushtail possums). However, this may be both undesirable and potentially counter-productive in some circumstances. Consequently, in recent years increasing attention has focused on changing livestock husbandry and farm management practices so as to reduce risks of disease transmission from wildlife to livestock. Here we present a brief review of husbandry and farm management practices that may influence disease transmission risks from wild to domestic mammals, with particular attention to bovine tuberculosis in the UK. We conclude that the manipulation of farming practices could potentially make a significant contribution to disease risk management. However, there are currently scant empirical data on risk reduction methods and further information will undoubtedly be required to inform husbandry best-practice.

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.

Quantitative trait loci (QTL) were identified for traits related to carcass and meat quality in Scottish Blackface sheep. The population studied was a double backcross between lines of sheep divergently selected for carcass lean content (LEAN and FAT lines), comprising nine half-sib families. Carcass composition (600 lambs) was assessed non-destructively using computerized tomography (CT) scanning and meat quality measurements (initial and final pH of m. semimembranosus, colour, shear force value, carcass weight, lamb flavour, juiciness, tenderness and overall liking) were taken on 300 male lambs. Lambs and their sires were genotyped across candidate regions on chromosomes 1, 2, 3, 5, 14, 18, 20 and 21. QTL analyses were performed using regression interval mapping techniques. In total, nine genome-wise significant and 11 chromosome-wise and suggestive QTL were detected in seven out of eight chromosomes. Genome-wise significant QTL were mapped for lamb flavour (OAR 1); for muscle densities (OAR 2 and OAR 3); for colour a* (redness) (OAR 3); for bone density (OAR 1); for slaughter live weight (OAR 1 and OAR 2) and for the weights of cold and hot carcass (OAR 5). The QTL with the strongest statistical evidence affected the lamb flavour of meat and was on OAR 1, in a region homologous with a porcine SSC 13 QTL identified for pork flavour. This QTL segregated in four of the nine families. This study provides new information on QTL affecting meat quality and carcass composition traits in sheep, which may lead to novel opportunities for genetically improving these traits.

Genetic parameters for carcass composition and meat quality traits were estimated in Scottish Blackface sheep, previously divergently selected for carcass lean content (LEAN and FAT lines). Computerized X-ray tomography (CT) was used to obtain non-destructive in vivo estimates of the carcass composition of 700 lambs, at ca. 24 weeks of age, with tissue areas and image densities obtained for fat, muscle and bone components of the carcass. Comprehensive measures of meat quality and carcass fatness were made on 350 male lambs, at ca. 8 months of age, which had previously been CT scanned. Meat quality traits included intramuscular fat content, initial and final pH of the meat, colour attributes, shear force, dry matter, moisture and nitrogen proportions, and taste panel assessments of the cooked meat. FAT line animals were significantly (P<0·05) fatter than the LEAN line animals in all measures of fatness (from CT and slaughter data), although the differences were modest and generally proportionately less than 0·1. Correspondingly, the LEAN line animals were superior to the FAT line animals in muscling measurements. Compared with the LEAN line, the FAT line had lower muscle density (as indicated by the relative darkness of the scan image), greater estimated subcutaneous fat (predicted from fat classification score) at slaughter, more intramuscular fat content, a more ‘yellow’ as opposed to ‘red’ muscle colour, and juicer meat (all P<0·05). All CT tissue areas were moderately to highly heritable, with h2 values ranging from 0·23 to 0·76. Likewise, meat quality traits were also moderately heritable. Muscle density was the CT trait most consistently related to meat quality traits, and genetic correlations of muscle density with live weight, fat class, subcutaneous fat score, dry matter proportion, juiciness, flavour and overall liking were all moderately to strongly negative, and significantly different from zero. In addition, intramuscular fat content was positively genetically correlated with juiciness and flavour, and negatively genetically correlated with shear force value. The results of this study demonstrate that altering carcass fatness will simultaneously change muscle density (indicative of changes in intramuscular fatness), and aspects of intramuscular fat content, muscle colour and juiciness. The heritabilities for the meat quality traits indicate ample opportunities for altering most meat quality traits. Moreover, it appears that colour, intramuscular fat content, juiciness, overall liking and flavour may be adequately predicted, both genetically and phenotypically, from measures of muscle density. Thus, genetic improvement of carcass composition and meat quality is feasible using in vivo measurements.

Genetic parameters were estimated using uni- and bi-variate random regression models for weight, eye-muscle depth and fat depth measures between 60 and 360 days of age. Each trait was measured up to five times in 50-day intervals following weaning on approximately 4000 Australian Poll Dorset Sheep. The model accounted for rearing type, dam age, management group and age of recording. The model used for analysing weight included quadratic, orthogonal polynomials for direct genetic and environmental effects, a linear polynomial for maternal genetic effects and heterogeneous error variance across ages. The fat and muscle analysis used linear orthogonal polynomials for direct genetic and environmental effects and heterogeneous error variance. Throughout the 300-day trajectory heritability for weight traits ranged from 0·20 to 0·31, while heritability for fat depth ranged from 0·24 to 0·34 and heritability for eye-muscle depth ranged from 0·24 to 0·40. Genetic correlations between repeated measures of the same trait at different ages were positive and declined as the age interval increased, to minimum values of 0·60, 0·31 and 0·50 for weight, fat and muscle respectively between 60 and 360 days of age. Genetic correlations between weight and fat and weight and eye muscle were moderate to high (0·6 to 0·8) and positive but decreased slightly with age. The genetic correlations between fat and muscle were moderate to high (0·5 to 0·7) throughout the 300-day trajectory. In all cases, the estimates produced in this study were reasonably consistent with the limited number of studies that exist in the reported literature. This study demonstrated the relationships that exist between repeated measures of weight, fat and muscle measures over time, which is of interest to prime lamb producers looking to select for specific breeding objectives or market end points requiring precise weight, fat and muscle combinations at certain ages.

The objective of this study was to evaluate effects of natural zeolite (clinoptilolite) on nutrient digestibility, carcass attributes and performance of Holstein steers given a diet containing urea. Forty-five Holstein steers (309 (s.d. 11·2) kg) were given diets as follows: control diet based on maize and soya-bean meal (SBM); treatment 2 (T2), control diet (without SBM) containing 20 g/kg urea; treatment 3 (T3), control diet (without SBM) containing 20 g/kg urea and 30 g/kg zeolite. Just before feeding, ruminal ammonia levels were low in all treatments. At 2·5 h post feeding, steers given T2 and T3 diets had higher ( P<0·05) ruminal ammonia concentration than the control. At 5·5 h post feeding, steers on T3 diet had the highest ruminal ammonia concentration, which was higher ( P<0·05) than the value for steers given T2 diet. Plasma urea nitrogen level increased post feeding for all treatments. At 3 h post feeding, the level for steers given T2 diet was higher ( P<0·05) than those on control and T3 diets but at 6 h post feeding, the level was higher for steers on T3 diet. No differences ( P>0·05) were observed in dry-matter intake among treatments. Live-weight gain and gain: food ratio were highest ( P<0·05) for steers on the control diet, with no differences ( P>0·05) between steers given T2 and T3 diets. Including zeolite in a diet containing urea had no effect ( P>0·05) on total tract digestibility coefficients of dry matter, organic matter and crude protein but increased ( P<0·05) digestibility of neutral-detergent fibre and acid-detergent fibre. Hot carcass weight and kidney, pelvic and heart fat weight of steers were highest in control, intermediate in T3 and least in T2 ( P<0·05). No differences ( P>0·05) were found in longissimus muscle area and fat thickness over longissimus muscle among treatments. Including 30 g/kg of zeolite in a diet containing 20 g/kg of urea decreased ruminal ammonia nitrogen concentration, plasma urea nitrogen level and increased fibre digestibility but its effect on feedlot performance was negligible.

Polymorphisms at codons 136, 154 and 171 of the gene encoding the prion protein (PrP) are associated with susceptibility to classical scrapie in sheep. Genetic selection for scrapie resistance based on PrP genotypes is central to the scrapie eradication programme in Great Britain but there are concerns about how this may affect other economically important traits. The objective of this study was to evaluate associations of PrP genotypes with live weight and slaughter traits in a hill sheep breed in Great Britain. Data used were from an experimental flock of Swaledale sheep in which the alleles ARR, ARQ, AHQ and VRQ were present. About 1450 genotyped lambs with birth, marking and weaning weights, and 620 with slaughter records were used for the study. Mixed models with various fixed effects and random direct genetic and maternal effects were tested to determine the appropriate model to use for each trait. None of the differences in lamb performance between PrP genotypes consistently reached significance. Therefore, this study does not support existence of significant relationships between PrP genotype and lamb performance traits in this breed.