Prion protein (PrP) genotype controls susceptibility to scrapie in sheep (Baylis, 2005) and a number of other transmissible spongiform encephalopathies including Creutzfeldt-Jakob disease in humans. Sheep have five PrP alleles (ARQ, ARH, AHQ, VRQ and ARR) and up to 15 PrP genotypes. In an attempt to control and eventually eradicate scrapie the GB National Scrapie Program (NSP, 2004) promotes the use of rams with scrapie resistant PrP genotypes (e.g. ARR/ARR) and discourages the use of scrapie susceptible genotypes (e.g VRQ carriers). Little is known about the effects of PrP genotype on sheep biology in general and commercially relevant production traits in particular. This study aims to determine whether PrP genotype is associated with production traits in a number of UK commercial sheep breeds, and results are reported here for the Charollais breed.

Several studies investigating associations between prion protein (PrP) genotypes and performance traits in several sheep breeds have recently been published. Most of these studies have failed to give conclusive results due to small numbers of animals used or a potential genotyping bias as those animals selected for PrP genotyping were chosen based on their performance (e.g. De Vries et al., 2005). Polymorphisms of the PrP gene has been linked with susceptibility to scrapie with the ARR allele generally associated with resistance and the VRQ with susceptibility. This study investigates the associations with PrP genotype for a wide range of lamb performance traits in experimental flocks of Scottish Blackface in which all animals have been PrP genotyped.

Genetic selection based on polymorphisms identified at codons 136, 154 and 171 of the prion protein (PrP) gene is being implemented in scrapie eradication programs (e.g. Defra, 2005). These programs aim to remove the VRQ allele (associated with the highest incidence of classical scrapie) and increase the frequency of the ARR allele (which confers the highest level of resistance). However, concerns remain about how selection on the PrP gene would affect other economically important traits. The objective of this study was to investigate potential associations between the PrP alleles and lamb traits in an experimental flock of Swaledale sheep, a hill sheep breed.

The benefits of adequate intakes of very long chain (VLC, carbon chain length ≥20) n-3 PUFA, in particular eicosapentaenoic acid (EPA, C20:5) and docosahexaenoic acid (DHA, C22:6) are well documented and crucially include a reduced risk of coronary heart disease. Although fish oils are a rich source of these fatty acids consumption of oily fish is low and it is now clear that in vivo synthesis of EPA and DHA from dietary α-linolenic acid is very limited, especially in men. This work assessed what the current dietary sources and intakes of EPA and DHA are, and how intake may be increased by enriching their concentration in foods of animal origin.

Alterations in utero result in adaptations that can alter the physiology of adult offspring a process known as “foetal programming”. Recent studies have shown that in adolescent ewes, low planes of nutrition in early pregnancy result in better reproductive performance (Annett and Carson, 2004). In adult ewes, responses are less clear. Some studies indicate no effect of nutrition level in early pregnancy on subsequent lamb output (Annett and Carson, 2004), whereas others indicate that low planes of nutrition in early pregnancy, reduced lamb output at weaning (Smeaton et al., 1999). Differences between studies may be due to residual effects of early pregnancy feeding on mid pregnancy. Consequently, the aim of this study was to evaluate the effect of different planes of nutrition in early and mid pregnancy on maternal and offspring performance.

Previous investigations have shown lamb vigour to be improved by including long chain omega-3 fatty acids in maternal diets during late pregnancy (Capper et al., 2003; Dawson and Edgar 2005; Pickard et al., 2005). However, these trials fail to elucidate whether there is a period in late gestation when supplementing diets with omega-3s would be optimal. Omega-3 fatty acids, particularly docosahexaenoic acid (DHA), are found in high concentrations in brain and nervous tissue (Arbuckle and Innis, 1993), and are therefore required at times of neural and brain tissue growth. This study explored the effects of feeding an algal source of EFAs, with a high content of DHA, during different time periods on measures of lamb viability.

Nutritional programming during early foetal life may play an important role in determining lamb vigour at birth, the development of the immune system and subsequently, lamb viability. However, information on the effect of macro and micro nutrient status of ewes during early pregnancy is limited. To address this, a research programme has been initiated at this Institute to investigate the effect of plane of nutrition and mineral status on foetal and lamb development and viability. The aim of the current study was to evaluate the effect of selenium supplementation from 14 days pre- to 90 days post-mating on maternal and offspring performance.

Supplementing pregnant ewes with the n-3 polyunsaturated fatty acids (PUFA) found in marine algae and fish oil increases gestation length and improves lamb vigour (Capper et al., 2002). However, continuing fish oil supplementation into lactation reduces milk component yield and lamb growth rate (Capper, 2005). The objective of the current experiment was to investigate the potential carry-over effects of feeding marine algae during pregnancy on ewe milk yield and composition during lactation and subsequent lamb growth rate.

Productivity of hill ewe flocks in Britain is dependent on both the genotype and viability of lambs born, with birth weight being a significant determinant of their neonatal viability and subsequent growth. Hill ewes lambing in late Spring frequently endure conditions of moderate to severe feed restriction during early pregnancy in their coincident winter environment. The extent to which such restriction has a negative impact on lamb birthweight, especially where the sire genotype has been selected for improved lean tissue growth, or is offset by safe mobilisation of maternal body reserves will be crucial to subsequent survival of the offspring. Nutrient demands imposed by the foeto-placental unit(s) depend not only on stage of gestation but also on litter size. They may also be influenced by the genetic potential for muscle growth of the foetal genotype, the expression of which is influenced by early pregnancy maternal nutrition (Fahey et al., 2005). In the present study we examined whether provision of a diet meeting 0.5 versus 1.0 times ME requirements for maintenance of pregnant ewes up to Day 95 of gestation influenced the birth weights of lambs. A total of 134 ewes lambed, 30 of these with twins. Sires used were Texel rams that were either carriers or non-carriers of the Inverdale fecundity gene (FecXI) gene.

The presence of very high levels of iodine in the diet of sheep in late pregnancy is subsequently associated with very low levels of immunoglobulins (Ig) in the blood of the lambs following consumption of colostrum (Boland et al., 2005). It remains to be established what minimum concentration of iodine in the diets of pregnant sheep affects IgG absorption, and whether the levels of iodine found in commercial concentrate feeds have an effect. The mechanism by which excessive iodine in the diet of pregnant sheep affects the absorption of Ig in lambs also remains to be established. The aims of this study were to determine the maximum dose of dietary iodine for late pregnant sheep that avoids the inhibition of IgG uptake from a standard quantity of colostrum given to neonatal lambs, and to examine the effects on thyroid hormone concentrations.

Although a considerable amount of research is being carried out in molecular genetics, few results have as yet found practical application in livestock breeding. In a previous study, quantitative trait loci (QTL) for growth and carcass traits were identified in commercial Texel and Suffolk sheep in the UK (Walling et al., 2004) and in Charollais sheep (McRae et al 2005). QTL were identified for muscle depth on chromosome 18 for Texel Sheep and Chromosome 1 for Suffolk and Charollais sheep. The current study aims to verify that QTLs for muscle depth found in commercial sheep are segregating in independent populations, and implement the technology required for the integration of genetic markers into commercial sheep breeding programmes.

There has been an increased interest in recent year in manipulating meat fatty acid composition, because meat is a major source of fat in the diet - particularly saturated fatty acids, which have been implicated in diseases associated with modern life. Conversely, polyunsaturated fatty acids (PUFA), which lower blood cholesterol concentrations, are present at low levels in meat, especially those of the n-3 series which are beneficial to health. Sales of meat have remained static or fallen slightly in recent years (Wood et al., 1999). This pressure on sales has caused a reappraisal of the factors which influence the appeal of meat to consumers, which together constitute ‘quality’, with one of these factors being the fatty acid composition. Like most animal production traits, fatty acid composition is influenced by both genetic and environmental factors, and the aim of the present study was to locate QTL affecting fatty acid composition in Scottish Blackface lamb meat.

Direct selection for fertility is difficult and yields little improvement because traditional parameters have low heritability and can only be measured in the mature female. A potential solution would be the use of an indirect selection criterion that is measurable in young bulls, is heritable and is genetically correlated to the fertility of the bull’s female progeny. The objective of this study was in investigate the genetic variation in free fatty acids (FFA), glucose, growth hormone (GH) and insulin concentrations in plasma from Danish male dairy calves following overnight fasting and the genetic covariation with fertility in their daughters.

A phenotypic and genetic decline in dairy cattle fertility has been reported in several countries simultaneous to the increase in genetic merit for production. In addition, an increase in atypical milk progesterone (MP4) patterns, particularly extended luteal phases, has been observed by Royal et al. (2000). One such MP4 parameter; the interval from calving to commencement of luteal activity (CLA), has been studied by Royal et al. (2002a,b; 2003) and is reported to have moderate heritability (h2), an unfavourable genetic correlation (rA)to milk yield (rA; 0.36) and a favourable rA to calving interval and interval to first service, respectively (0.39, 0.53). Although CLA is a good indicator of onset of luteal activity (LA) postpartum (pp), it does not take account of subsequent ovarian activity. The objective of this study was to investigate an alternative MP4 parameter using the proportion of MP4 samples representing LA within the first 60 days pp in both British and Swedish dairy cows.

The ability of high-yielding modern dairy cows to perform in the range of systems found on UK dairy farms and to be profitable and sustainable needs investigating. As part of a project to study the robustness of such animals, milkprogesterone profiling was used to investigate the reproductive performance of two genotypes of dairy cow on two production systems. The use of milk progesterone profiles to give a detailed picture of oestrus cycle activity and fertility in dairy cows has been described by Royal et al. (2000).

Many studies have shown the negative impact of high production on functional performance in the dairy cow (e.g. Dechow et al., 2002). It is suggested that the increased capacity for milk production has resulted in the partial “shift” of nutrients away from maintaining functional fitness towards production output. Bull profiles for daughter body energy traits were produced using random regression techniques. The relationship of functional traits with body energy traits across 1st lactation was examined. If body energy is correlated with health and fertility it could indicate that high metabolic stress leads to deterioration in one or more of these traits.

Subfertility in lactating cows has a multifactorial background, but a significant cause may be the negative energy balance (NEB) associated with early lactation. One effect of NEB is to delay the interval from calving to first ovulation. The likely candidates for mediating the effects of NEB on reproductive function are the metabolites and metabolic hormones that change in relation to physiological and nutritional state. Circulating IGF-I concentrations fall post partum and both IGF-I and insulin concentrations influence the interval from calving to first ovulation, follicular oestradiol production, and the number of ovulatory oestrogen-active follicles. Moreover, cows with higher IGF-I concentrations after calving generally ovulate within 35 days. Effects of circulating IGF-I on developing follicles are influenced by IGF receptor concentrations and local production of specific binding proteins (IGFBPs). We postulated that severe NEB compromises the early stages of follicular growth via alterations to the follicular IGF system.

The liver is the principle site of production of both insulin-like growth factor (IGF) and the associated binding proteins (IGFBPs). During lactation, tissue reserves are mobilised and gluconeogenesis in the liver is up-regulated. The high nutrient demands of lactogenesis result in a physiological state of negative energy balance (EB), a situation that has profound effects on the IGF system. It is also known that the IGF family members play an important role in fertility by acting on reproductive tissues. Genetic selection of dairy cows for high yield milk production has led to a decline in fertility and it is thus hypothesised that this disruption is a consequence of down-regulation of certain IGFs and/or their receptors and binding proteins. In this study a qPCR approach was used to quantify the expression levels of specific transcripts of the IGF family in the liver during different situations of mild or severe energy balance.