The putative Thoka gene, with large effects on fecundity, originated in Icelandic sheep. The gene was introduced to the UK in 1985 through a programme of crossbreeding and established in Cheviot sheep (Russel et al., 1997). Ewes have been retained in the flock as putative Thoka gene carriers if they have lambed in each of the first three years and had at least two sets of twins. Progeny tests on a separate population of ewes have been used on two occasions to identify rams believed to carry the gene. Despite this complex breeding programme, the actual segregation of a gene for fecundity has yet to be unambiguously demonstrated in this flock. The purpose of this study is to use complex segregation analysis to demonstrate the existence of this gene, estimate the size of its effect and frequency of the favourable allele within the population.

Ewe prolificacy, lamb survival and early lamb growth are economically important traits, playing a major role in determining the profitability of hill sheep farms (Conington et al., 2000). In currently advocated selection strategies these traits are usually expressed as traits of the dam, however, relatively low heritabilities limit the genetic progress achievable (Conington et al., 2001). An alternative approach is to treat these traits, where appropriate, as traits of both the ewe and lamb. This study investigates reparameterisation of these traits as joint expressions of both lamb and ewe genotype, and considers the impact of the results on currently-advocated selection strategies.

Shape of the carcass is considered important commercially and is usually assessed using a subjective score for conformation. Carcasses of higher conformation are perceived to have higher lean to bone (L:B) ratios and give joints of better shape at a weight, characterised as shorter and having a greater thickness of muscle. Some of these benefits have been shown, but so has a positive association between conformation and fatness. Purchas et al. (1991) proposed that muscularity indices could be used as an alternative to the conformation score. The objectives of this study were to investigate the relationships between muscularity, shape of joints and composition within breeds and the relationships between different muscularity indices. Knowledge of the latter relationships is important to determine how many indices are required to adequately describe carcass muscularity.

With individual genes being identified that have an important effect on performance and fitness in livestock it is likely that such genes will be included in selection programmes. However, in order to devise sensible strategies to achieve this, knowledge of the frequency of the gene of interest is required. In practice, it is possible that estimates for gene frequency are based on genotype testing of only a subset of the population. The question then arises as to what conclusions can be drawn about the population gene frequency particularly in the likely scenario where the sample genotyped is not chosen at random. A procedure was developed by Van Arendonk et al. (1989) to have genotype information on as many individuals as possible given financial limits in the numbers genotyped. In this procedure the genotypes of individuals are predicted using pedigree information and the rules of Mendelian inheritance. What is less clear is the value of the additional information in predicting the population gene frequency. The objective of this study was to assess to consequence of sampling procedures on estimates of gene frequency when additional genotype information is or is not obtained by predicting genotypes on individuals themselves not tested.

At a time of high public awareness of food safety issues, particularly with respect to transmissable encephalopathies, and a government policy to eradicate scrapie, there is increasing pressure for breeders to select for scrapie resistance in sheep. Genetic variation has been identified at the PrP locus that confers differing degrees of susceptibility to scrapie. In the Suffolk breed this variation is confined to amino acid variations at codon 171, resulting in two alleles R and Q. Animals with the genotype RR and RQ show a greater degree of resistance to scrapie than animals with genotype QQ (Hunter, Moore, Hosie, Dingwall and Greig, 1997).

Genotyping of pedigree animals has now become routine for many breeders and RR animals are favoured. It is, however, unknown whether there is a relationship between PrP genotype and performance traits. The objective of this study was to analyse the relationship between PrP genotype at codon 171 and the performance traits included in the Lean Index (Simm and Dingwall, 1989), which is used for selection in the Suffolk breed.

The mixing of unfamiliar sows at weaning leads to aggression whilst dominance hierarchies within the group are established (Kay et al, 1999). The objective of this study was to determine whether the presence of a boar would reduce the incidence of aggression and level of skin damage of newly mixed sows. The overall aim of the project was to improve welfare by designing a suitable strategy for mixing groups of newly-weaned sows

In recent years, there has been increased interest in the development of non-invasive methods to assess the welfare status of an animal. The objectives of this study were to determine the suitability of using heart rate variability analysis as a measure of autonomic activity in pigs during various behaviours and to determine whether these measures were influenced by stage of gestation.

Increasing the group size of weaned pigs can lead to more efficient use of resources by producers. However research with finishing pigs suggests that increasing group size can also lead to increased aggression and reduced performance (Spoolder et al., 1999). The objective of this study was to assess the effect of group size on the performance and behaviour of weaned pigs.

UK legislation dictates that all pigs shall have access to straw or other material or object suitable to satisfy their behavioural needs (Welfare of Livestock Regulations, 1994). However, it is unknown how much straw must be provided to be behaviourally rewarding, and whether pigs’ prior experience of straw can impact upon their subsequent behavioural needs. Therefore, the aim of the current experiment was to investigate these issues by exposing pigs which did, or did not, have prior experience of straw to four levels of straw bed depth.

Harmful social behaviour is behaviour that is directed at pen mates which, if persistent, causes injury. It includes tail, ear and flank biting. The aim of this work was to determine if pigs that are predisposed to harmful social behaviour can be identified early in life using a test. In this experiment a test that measured the chewing behaviour of pigs on an artificial tail was developed from Fraser (1987), as one of a wider battery of tests under investigation in the overall project. The validity of the test was evaluated by correlating the rope directed behaviour in the test with harmful social behaviour in the home pen.

Fat and muscle reserves are mobilised during winter by breeding hill ewes, living in harsh environments, as they conceive and carry their lambs (Russel et al., 1968). Tissue depletion and repletion were studied in Scottish Blackface ewes through one productive cycle using computed tomography (CT). The aim was to use this nondestructive method to quantify patterns of change in carcass fat, carcass muscle and internal fat in ewes of differing age and reproductive status.

To what extent different fat depots of the carcass are more or less useful to the animal as readily labile energy stores is not clear. A knowledge of how ewes partition and use fat within the carcass is vital in order to estimate the impact of selection to reduce subcutaneous fat on other carcass fat depots. This study was designed to describe changes in the different carcass fat depots over one annual production cycle.

The effective rumen degradability (ERD) of dietary protein is used to quantify the amount of dietary protein entering the small intestine of ruminants. Midwinter shearing of prolific ewes increases rumen degradation rate (Kd) of dietary protein (Šebek and Everts, 1999). However, these differences in Kd may be compensated by a different rumen passage rate (Kp), since cold exposure is often associated with increases in Kp. Kp can be estimated by use of an undegradable marker. This method, although reliable for fluids seems less reliable for solids. The objective of the present experiment was to quantify the effect of midwinter shearing on ERD in highly prolific ewes. As an alternative to the use of Kp, ERD of crude protein (CP) and of protein-free-organic-matter (OM_CP) were estimated from periodical changes in rumen volume partitioned as rumen degradable (Xd) and rumen undegradable (Xu) components.

Fishmeal is a suitable protein source for pregnant and lactating ewes, providing higher levels of undegradable protein than vegetable protein sources, with an improved biological value (Robinson, 1987). Vegetable protein sources may however be improved by formaldehyde treatment to reduce protein degradability and by the addition of rumen-protected amino acids. The objective of the current experiment was to compare the effects of feeding concentrates containing fishmeal with concentrates containing soya-bean meal, formaldehyde treated soya-bean meal and formaldehyde treated soya-bean meal with rumen-protected methionine.

In previous research the benefits of grass feeding in lambs for healthiness (fatty acid composition) and flavour have been demonstrated (Fisher et al., 2000). This work examined a very short period of feeding grass or concentrates in a hill breed (Beulah) and a breed noted for meat production (Texel).

Colour deterioration and lipid oxidation are major factors limiting the shelf life and acceptability of meat. Vitamin E slows down these processes and meat from animals fed supranutritional amounts of vitamin E has an increased shelf life. However, vitamin E supplementation in sheep has produced variable results (Enser et al. , 1999). This work shows the effects of supplementing vitamin E on the concentration in plasma over a 63 day feeding period and on meat quality.

The polyunsaturated fatty acids (PUFA) of the intramuscular phospholipids are the most significant lipids in the development of cooked beef flavour (Mottram and Edwards, 1983). In lamb, differences in n-6 and n-3 fatty acid composition have been shown to be a major factor influencing consumer perception and acceptability (Sañudo et al, 2000). Altering meat PUFA, especially n-3 fatty acids, to improve its value in human nutrition (COMA, 1994) may have effects on flavour and acceptability. The aim of this work was to evaluate differences in flavour perception when intramuscular fatty acid composition is changed in beef meat.

Quality of lamb meat is a topic of great importance to both retailers and consumers and has received considerable attention over the past few years (Wood et al. 1999). First of all, the theme is important for the future of sheep production. Sheep producers operate in competitive market and their survival is threatened because sheep meat is continually facing challenges to maintain/increase its market share. Second, it relates to the emergence of specific market desires. In this respect, it has been suggested that lamb meat, which meets the demands of individual markets, should be the objective if sheep production is to remain competitive (Sanudo et al. 2000). The objective of the current study was to investigate the effects of post-weaning nutrition and degree of maturity (or live weight at slaughter) on the eating quality of lamb meat produced by three dairy Greek breeds of sheep.

The basis of diet selection for protein in ruminants remains unclear. Tolkamp et al., (1998) proposed a hypothesis to account for the conflicting findings. They proposed that ruminants select their diet on the basis of effective rumen degradable protein (eRDP) rather than for MP yield. As the protein supply of ruminants comes largely from microbial protein, the idea that ruminants select a diet that meets the requirement for eRDP, which is captured and utilised by the microbes to produce microbial protein, is not an unreasonable one. The objective of this experiment was to test the hypothesis that both inadequate and abundant eRDP levels would be avoided by growing sheep when given choices of foods.

It was hypothesised that both inadequate and abundant levels of effective rumen degradable protein (eRDP) would be avoided by ruminants given a choice of foods (Tolkamp et al, 1998). However, we have found that sheep do not appear to avoid the excess consumption of eRDP expected when they were offered a choice of foods that differed in eRDP content through the addition of urea to one of the foods (James et al., 2001). A possible reason could be due to the fact that the foods offered had low fibre contents. The sheep may have selected for the urea supplemented food in an attempt to buffer the rumen. The buffering ability of the urea could help to minimise the disruption of the rumen such as a fall in pH caused by the low fibre foods. The objective of this experiment was to test the hypothesis that the preference for the urea supplemented food would be reduced by the addition of sodium bicarbonate (buffer).