The majority of market lamb produced in UK results from crossing terminal sire rams with crossbred ewes. The selection of terminal sire breeds over the past 15 years for improved carcass composition has shown positive benefits on carcass quality of their crossbred progeny (Simm et al. 2001). However, faster rates of genetic improvement would be achieved if information from these terminal sire crossbred lambs could be used in the genetic evaluation of terminal sire breeds. Incorporating crossbred information into purebred selection programmes has been modelled and the results show that it is an effective way of improving carcass quality (Jones et al. 1999). However, this is currently compromised by limitations on how individual carcass data can be collected for incorporation into breeding programmes. An innovative technology based on Video Image Analysis (VIA) of lamb carcasses is being evaluated for introduction into UK lamb abattoirs. VIA systems can provide an objective, automatic, consistent and accurate way of measuring carcass composition. However, little is known of genetic parameters for VIA measurements of lamb carcasses. Therefore the aim of the present research project was to estimate the genetic parameters of VIA carcass measurements in crossbred lamb population.

Breeding indices that combine carcass and maternal performance traits have been tested in practice and result in significant improvements in lamb growth. However, subjective carcass grades for fatness and conformation did not differ as a result of 7 years of selection on the index (Conington et al., 2006). Instrumental grading systems with the potential to objectively and accurately predict carcass composition and muscularity using video image scanning (VIA) may become standard in the UK for lamb carcass grading in the future. The use of computer tomography (CT) scanning of lambs in sheep breeding programmes is likely to better predict the carcass and prime cut VIA-assessed traits and hence lead to accelerated progress in carcass traits. This paper assesses the impact of including CT-derived carcass traits in breeding programmes for hill sheep and the consequences on traits related to maternal traits and lamb survival.

Hill sheep flocks in the UK are dominated by purebred ewe genotypes, with the Scottish Blackface, Welsh Mountain and Swaledale being the most common. However recent changes to the Common Agricultural Policy have lead many hill producers to consider keeping crossbred ewes on the hill, with the aim of introducing complementary traits to increase lamb output and improve carcass quality. In 2001 a major on-farm research programme was initiated on 6 hill farms around Northern Ireland to evaluate lifetime performance of a range of crossbred ewe genotypes. Provisional data has already identified that retaining Lleyn X Blackface and Texel X Blackface ewes can improve lamb output at weaning by up to 10% relative to purebred Blackface ewes (Speijers et al., 2007). The aims of the current study were to investigate the effects of switching to crossbred hill ewe genotypes on lamb performance during finishing.

Resistance to gastro-intestinal (GI) nematode infection in sheep may be partly attributed to host genetic variation. Faecal egg count (FEC) of an individual is an important indicator trait that measures the relative resistance of sheep to GI nematode infections. The FEC can be measured easily and repeatedly over short time intervals, and its genetic properties and utility as a selection tool are well understood (Bishop and Stear, 2001). However, FEC is the result of a complex series of host-parasite interactions that depend on host genetics and immunological mechanisms, epidemiology of the disease, and other non-genetic measures. The objective of the present study was to determine, in silico, underlying host immunological mechanisms that could lead to observable major genes for FEC. To achieve that, we have extended the stochastic genetic epidemiological model for nematode infection in sheep as described by Bishop and Stear (2001), and used complex segregation analyses to explore the genetic properties of the simulated FEC data.

The relative susceptibility to classical scrapie is mainly determined by polymorphisms at codons 136, 154 and 171 of the prion protein (PrP) gene (Hunter et al., 1996). Five haplotypes, defined by the combination of variants at these three codons are commonly found in sheep; scrapie eradication programmes in several countries are based on changing their frequencies. In Suffolk sheep, one codon shows variation, with the R allele associated with resistance and the Q allele associated with susceptibility. Genotyping costs may be reduced by utilizing information from relatives to infer the genotypes of other relatives. The objectives of this study were to determine the effectiveness of predicting PrP genotypes using information from relatives and to investigate the association of PrP gene with lamb performance traits in Suffolk sheep.

Scrapie is a degenerative disorder of the central nervous system of small ruminants. Scrapie in sheep appears to be controlled by genetic factors, with polymorphisms at codons 136, 154 and 171 of the PrP gene locus being the determining parameters (Hunter et al., 2005). Individual PrP genotypes are detected primarily with blood or ear notch tissue samples. Increasingly strict regulations on food safety and public hygiene require new, practical, animal friendly methods for large scale implementation. The first aim of this study was to develop a novel genotyping method using DNA extracted from milk somatic cells from individual animal samples. The second aim was to develop a quick, easy and accurate method for assessing the prevalence of undesirable genotypes within each flock using bulk milk.

Gastrointestinal parasitism is estimated to cost the British sheep industry £83M per annum and these losses could be reduced by breeding sheep with enhanced resistance to parasites (Nieuwhof and Bishop 2005). However, there is concern that parasites could adapt to more resistant hosts through the increased selection pressure placed on parasite populations. The aim of this study is to evaluate the potential of Trichostrongylus colubriformis to adapt to host genotype following long-term exposure. We hypothesised that T. colubriformis would adapt, as measured by egg output, differentially to hosts selected for either increased (IR) or decreased (DR) parasite resistance following long-term serial passage.

Trans-10, cis-12 CLA is produced as an intermediary during the biohydrogenation of linoleic acid (C18:2 n-6) in the rumen and has been shown to be a potent inhibitor of milk fat synthesis in ruminants. The production of trans-10, cis-12 CLA in the rumen is affected by dietary concentrate: forage ratio (Kucuk et al., 2001), rumen pH and the amount and source of linoleic acid in the diet. However, the interaction between oil source, carbohydrate source and pH on the production of trans-10, cis-12 CLA is unclear (Beam et al., 2000). The objectives of the current study were to determine the effects of oil source, carbohydrate source and pH on the biohydrogenation of linoleic acid and production of trans-10, cis-12 CLA in vitro.

As a result of human nutritional recommendations, experiments have been performed to modify milk fatty acid (FA) composition in order to increase milk content of C18:3 n-3 and to decrease that of both deleterious saturated FA and trans FA. The modifications observed when cow’s diet is supplemented with a source rich in C18:3 n-3, such as linseeds, are largely dependent on rumen biohydrogenation processes. Indeed, milk trans FA and C18:3 n-3 are a consequence of the ruminal biohydrogenation of dietary C18:3 n-3. However, little is known about the effect of increasing amount of extruded linseeds intake by cows on the kinetics of rumen biohydrogenation. This may impact human health because it could affect both the amount of C18:3 n-3 and of trans FA available for milk fat production. Trans FA profile may be important to consider because their side effect on human health may be due to specific trans FA. The aim of this study was thus to assess the effects of increasing intakes of extruded linseeds on kinetics of rumen FA profile, especially trans FA.

The level of red clover polyphenol oxidase (PPO) activity can be greatly increased following cell damage. This is probably due to activation of latent PPO by quinone products of phaselic acid produced by the constitutive active PPO, which is normally at a much lower level than the latent PPO. This “self activation” of PPO following tissue damage could act as an indicator of the level of tissue damage in a conditioned red clover crop. This study investigated a range of tissue damage levels with the PPO activation state and activation with bound-phenol formation in an attempt to correlate degree of cell damage with PPO activity.

Polyphenol oxidase (PPO) had been shown to reduce both proteolysis and lipolysis in incubated red clover (Lee et al. 2004). However it has not been determined whether rumen microbes can adapt to utilise PPO protected protein and lipid. This study investigated whether rumen inoculum from cows offered red clover silage resulted in higher levels of proteolysis and lipolysis in red clover (+PPO) and also in red clover with the PPO1 gene silenced (–PPO) (Sullivan and Hatfield, 2006), than rumen inoculum from cows offered grass silage, due to microbial adaptation.

Lee et al. (2007) showed that red clover; with the PPO1 gene silenced (Sullivan and Hatfield 2006), exhibited higher levels of lipolysis than the wild type in the presence of rumen micro-organisms. This questioned the hypothetical mode of action of polyphenol oxidase (PPO) being solely deactivation of the plant enzymes and implied some level of protection of the red clover lipid. It was hypothesised that this may be as a result of protein-phenol complexes, formed by the action of PPO, complexing around lipid micelles and so offering a level of protection. This study investigated whether red clover lipid is protected in the absence of such protein matrixes. At the same time levels of free amino acids were monitored in cultures with the protein matrixes formed to determine whether these offer any form of protection from microbial degradation.

As grazing ruminants rely almost entirely on mastication to disrupt plant tissues, a series of processes (mastication, bolus formation and ingestion) will impact on the viability and number of cells that remain intact, and consequently alive, after ingestion (Kingston-Smith and Theodorou, 2000). Preliminary work in our group has shown substantial variation in the degree of cell damage during mastication and ingestion between grass species, resulting in differences in the rate of release of cell contents (protein, sugars and lipids) into the rumen (E.J. Kim, unpublished). These differences may affect nutrient utilisation by ruminal micro-organisms. The aim of this study was to compare the extent of nutrient release from three contrasting grass species following ingestion of the fresh forage by dairy cows.

In mid season prime lamb production Keady and Hanrahan (2006) concluded that increasing litter size and good grassland management are the main factors affecting efficiency of production. Nolan (1972) reported lamb carcass outputs of 203 and 301 kg/ha from grass-based systems which received 77 kg N/ha and were stocked with 10 and 15 Galway ewes (mean litter size of 1.4 lambs) per hectare, respectively. Subsequently the Belclare breed was developed (Hanrahan 1997) as a genetic resource for increased prolificacy. Recently there has been interest in either reducing or eliminating the winter indoor feeding period by extended grazing. Recent studies at this Centre have shown that extended grazing in mid, late or throughout pregnancy increased lamb birth and weaning weights relative to progeny from ewes which have been housed unshorn (Keady et al 2007). The primary objective of this study was to evaluate two contrasting grass-based systems for prime lamb production. The systems adopted compared maintaining the stocking rates and levels of fertilizer nitrogen application similar to that of Nolan (1972) but increasing lamb carcass output through improved genetic capacity and either housing the flock during the winter period or maximising the use of grazed grass by year round grazing. Two ewe genotypes were used to examine if there were any interactions between level of prolifacy and the grassland based system of production adopted.

Consumption of milk and milk products contributes 14-15% of total dietary fat intake by adults in Great Britain, and provides 23-25% of total saturated fat intake. The relationship between dietary fat intake and incidence of coronary heart disease is well established and current recommendations are that total fat consumption should not exceed 35% of daily food energy intake and that saturated fat intake should not exceed 11% of daily food energy. Studies have shown that different saturated (SFA) fatty acids can have different effects on plasma lipoprotein cholesterol levels and that replacing SFA and trans (TFA) fatty acids with cis-unsaturated (USFA) fatty acids has a favourable effect on total and LDL-cholesterol levels (Zock, 2006). The present study aimed to apply dietary modification of the dairy cow diet to produce milk fat with a healthier fatty acid profile to meet human dietary recommendations.

Canola meal (the oil-free residue of low glucosinolate, low erucic acid rapeseed) is a good source of protein for animals and is a particularly rich source of the sulphur containing amino acids, methionine and cystine. Canola meal has some antinutritional factors that they may be responsible for low utilisation of nutrients in the canola meal. These antinutritional factors are glucosinolates, erucic acid, phytic acid and high levels of fibre. Removal of undesirable components is essential to improve the nutritional quality of meals and effectively utilise their full potential as animal feed. Several conventional food processing methods such as germination, soaking, cooking and fermentation are known to reduce antinutritional factors and upgrade the nutritional quality of feeds of plant-origin. However, most of these treatments adversely affect the sensory characteristics of the final product. Food irradiation has been recognised as a reliable and safe method for preservation, improving hygienic quality and improving the nutritional quality of foods (Diehl, 2002).

The rumen ammonia level (AL) is the key intermediate in the microbial degradation and synthesis of protein. Measurement of ruminal AL reflects the balance achieved between protein breakdown and synthesis under special dietary circumstances. If the diet is protein deficient or its protein resists degradation, the rumen AL will be low and the rumen microbial growth will be slow. Conversely, if protein degradation is faster than synthesis, rumen AL will accumulate in excess of its optimum level. Excess AL is absorbed into the blood, and converted into urea via liver. Major part of urea is excreted in the urine as a waste causing pollution to the environment. This study examined the effect of various spices when incubated with different forages in rumen fluid (RF) in vitro for different times on AL.

In developing countries, low quality forages, like cereal straws are the main basal feed for ruminants. But these forages are low in energy, protein, vitamin and minerals. Most of the carbohydrates of these forages are bound to compounds like lignin, silica, phenolic, oxalate etc and so the ruminants cannot utilize these forages effectively which affect ruminant health and production. So it is needed to improve the quality of these forages. Herbs and spices which are being safely used for human consumption for a long time may help improve the rumen fermentation and hence the utilisation of these forages if offered to the forage consuming ruminants. This study compared the effects of various levels of four commonly used spices on the in vitro dry matter (DM) degradability (IVD) of these selected forages at different times.

In order to reduce the dependence of the ensiling process on epiphytic lactic acid bacteria (LAB) and on chemical additives, inoculants comprising homofermentative bacteria such as Lactobacillus plantarum, Enterococcus faecium, and Pediococcus species, are often used to control the ensiling fermentation by rapid production of lactic acid and the consequent decrease in pH and improved silage preservation with minimal fermentation losses (Filya, 2004; Muck & Kung,1997). The objective of this study was to determine the effect of microbial inoculation on the fermentation of corn silage treated with Lactobacillus plantarum and Propionibacterium acidipropionici silage inoculants and the subsequent effect on nutritive value and performance by lactating beef cattle.

Silage making is one of the main conservation methods that is used in forage preservation (Muck, 1993b and Cassida, et al. 1994). Application of silage additives is the most important factor in improving silage quality (Muck, 1993a). Canola is one of the crops that produce throughout the world. Since, canola could not reach to stage of blossom in some climates such as cold climate, so farmers should mow and making silage for animal nutrition. The objective of present study was to determine the effects of different additives on chemical composition of whole crop canola silage.