Myostatin acts as a negative regulator of muscle growth. Mice and cattle deficient for myostatin have a dramatic increase in skeletal muscle mass (McPherron et al., 1997, Arnold et al., 2001). Natural mutations in the myostatin gene have been seen in several cattle breeds and in one mouse line and in cattle the associated phenotype is referred to as ‘ Double-muscling’ (DM). Although the direct DM effect seems to be positive in meat producing livestock with increased muscle and decreased fat there are reports of negative side effects in reproductive and other traits in cattle, with an indication of substantial interaction with the genetic background (Wiener et al., 2002). Thus it may be possible to select for the beneficial traits, while minimising the impact of the negative effects. Although negative side effects are not fully understood, breeding companies in the meat-producing sector are devoting considerable effort to high-throughput screening for mutations in this gene, hoping to find variants associated with increased muscularity. It is important that the impacts of such mutations on a wide range of production and welfare traits are fully explored before it becomes a focus of selection in meat producing livestock. The objectives of the work presented here were to utilise marker assisted introgression of a myostatin-deficiency producing partially recessive allele (Compact, MstnCmpt-dl1Abc) to estimate its effects on traits of growth and fitness on the genetic background of an extreme high growth line, as a model of a highly developed livestock breed. Fitness effects as assessed by the segregation ratio are reported here.

Factors such as breed, sex, stage of maturity, stage of reproduction and nutrition are known to affect the amount and distribution of fat in different body depots of sheep. Between-breed differences may occur in fat distribution between different body regions, or between different depots (e.g. carcass / internal fat). For example, breeds selected for milking or maternal traits tend to deposit relatively large proportions of internal fat, whilst meat breeds deposit more carcass fat (Wood et al., 1980; Thompson and Ball, 1997). The aim of this study was to compare levels of fat in different body depots between Scottish Blackface and Texel lambs at finishing.

Recent research has focused on a component of ruminant fat, conjugated linoleic acids (CLA), which have been implicated with numerous health promoting properties including anti-carcinogenicity (Belury, 1995). Dietary supplementation with CLA has been shown to have a marked effect on tissue composition in several species, although there is apparently no evidence of such effects being seen in sheep (see Salter et al., 2002). Consequently, the aim of this study was to examine the effect of feeding growing lambs a CLA supplement, protected from rumen degradation, on carcass characteristics and tissue CLA content.

Ruminant products are considered as a major source of saturated fatty acids (SFA) in the human diet and a reduction in the intake of SFA along with a concomitant increase in the intake of n-3 series PUFA is recommended by nutritionists (Department of Health, 1994). The major fatty acid classes in beef are the saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) and beef is a nutritionally important source of the beneficial n-3 series PUFA. Experiments investigating the effects of age on lipid composition in beef muscle have, in the main, used short time periods and also been subject to confounding effects of differences in growth rate (Rule et al., 1997). This study is part of a larger investigation into the effects of breed and diet, as well as age, on muscle lipids (Warren et al., 2003). This paper will focus on the effect of age.

Fatty acid composition and vitamin E content of beef are affected by breed, diet and age, with implications for meat quality. The effects on shelf life and flavour were investigated in this project.

Under controlled experimental conditions, ruminally protected lipid supplements (PLS) rich in 18:2n-6 and 18:3n-3 have been successful in creating large shifts in the fatty acid composition of beef muscle (Scollan et al., 2003). However, there is a need to test methodology under commercial conditions and with a wider range of breed types. This study was conducted at a Yorkshire Farm and used Charolais Cross and the Stabiliser breed, a mix of 5 breeds designed to combine efficient production and good carcass quality.

Fat of ruminant origin is one of the main dietary sources of conjugated linoleic acid (CLA), considered to have several human health promoting properties. Production of CLA occurs during ruminal biohydrogenation of dietary linoleic acid and by tissue desaturation of trans-vaccenic acid (TVA) produced during ruminal biohydrogenation of linoleic and linolenic acid. Wilting of grass prior to ensiling decreased the content of linolenic acid (Dewhurst et al., 1998), which may decrease CLA synthesis. Dietary inclusion of a source of long-chain polyunsaturated fatty acids (P), such as fish oil may limit the extent of biohydrogenation of shorter-chain P leading to an accumulation of CLA and TVA (Wonsil et al., 1994). The objective of this study was to determine the effect of inclusion of fish oil in the supplementary concentrate and wilting of grass prior to ensiling on the fatty acid composition of beef intramuscular adipose tissue.

Effective ruminal protection of dietary polyunsaturated fatty acids (PUFA) is very useful in helping to reduce microbial biohydrogenation of PUFA and results in major improvements in the ratio of polyunsaturated:saturated fatty acids (P:S) in beef muscle (Scollan et al., 2003). However, in that study the protected lipid study (PLS) used which consisted of soya beans, linseed and sunflower oils mixed to give a 2.4:1 ratio of 18:2n -6:18:3n -3, was less successful in improving the n -6:n -3 ratio in beef muscle. This study reports the effects of including in the diet a PLS with a lower ratio of 18:2n -6:18:3n -3 on the fatty acid composition of the m. longissimus.

There is an increasing body of evidence to support the view that the periparturient breakdown of immunity to parasites has a nutritional basis (Houdijk et al., 2003). Nutritional improvement of expression of immunity to parasites has been assessed indirectly through changes in faecal egg counts (FEC) and worm burden. A direct assessment of effector responses is hampered by its local nature and would be limited to analysing gut tissue samples obtained at slaughter. However, recently an abomasal cannulation methodology was developed that allows for serial sampling of the abomasal mucosa throughout the periparturient period in sheep (Huntley et al., in press). Here, this methodology was used to assess temporal effects of metabolizable protein (MP) supply to parasitized, periparturient sheep on abomasal inflammatory cells that are associated with expression of immunity to nematodes.

Nutrition of the ewe during early pregnancy has important implications for lamb output through its effects on implantation and early embryonic development. In adolescent ewes a high plane of nutrition during the first half of gestation has been found to reduce conception rate, lamb birth weight and neonatal lamb survival (Wallace et al., 1996). However few studies have examined the effects of nutrition immediately post-mating on foetal development and subsequent lamb performance. The current experiment was set up to investigate how plane of nutrition of adolescent and mature ewes during the first month after mating affects lamb output, foetal development and lamb growth.

In recent years there has been increasing use of mineral blocks in the diets of sheep both at mating time and in pregnancy. However, recent work carried out at this institute (Joyce, 2000) found that lambs whose dams had access to mineral blocks had significantly lower IgG serum values at 24 hours than lambs whose dams had no access to mineral blocks. This experiment investigated further the effects of supplementing the pregnant ewe diet with mineral blocks on IgG absorption efficiency and on the level of faecal adhesion to the tail-end of the lambs in early life.

The placenta prevents the transfer of maternal immunity to the foetus and consequently lambs are born hypoimmunocompetent. The IgG content in colostrum and its absorption into the blood stream has important consequences for lamb liveability in early life. Recent experiments carried out at this institute found that when ewes had access to a mineral block or the mineral component of this block in the form of powdered minerals in late pregnancy, the absorption of IgG by their offspring was reduced (Boland et al., 2003). Keane (2001) stated that it would appear that the lamb was pre-programmed in-utero for lowered IgG efficiency and that the problem lay with the lamb rather than to any altered characteristics of the colostrum. The aim of this experiment was to investigate the period of time necessary for high levels of mineral supplementation to the ewe to affect a reduction in IgG values in the progeny.

High levels of mineral supplementation to ewes in late gestation results in reduced blood serum immunoglobulin G (IgG) concentration and a lowered efficiency of colostral IgG absorption at 24h post partum (Boland et al., 2003). Given that lambs are born hypogammaglobulinemic and are dependent on the absorption of immunoglobulins from colostrum for immunity in early life, this decrease in serum IgG concentration is likely to present a significant challenge to the neonatal lamb in relation to disease susceptibility. The aim of this experiment was to determine which element(s) in the mineral supplement are having the greatest effect in reducing colostral IgG absorption and if the removal of this element(s) from the formulation would result in a return to what might be considered as normal immunoglobulin absorption values.

Since the ban of meat and bone meal and fishmeal the UK farming industry has turned to soyabean meal as the major source of protein for inclusion into ruminant diets. Public concerns over GM foods and traceability of foodstuffs have turned attention to home-grown protein sources such as legumes. Peas have historically been fed as meal, however, the use of whole-crop peas as silage is a relatively new idea. The presence of condensed tannin (CT) has the potential to ruminally protect protein from degradation (Min et al., 2003). However the degradation characteristics of different pea silages varying in CT have not been determined. This experiment tested the hypothesis that pea silage with a higher CT level would have a reduced effective degradability.

The combination of genotypes (100% stress negative) and other treatments, especially nutritional, can give good results in achieving fast lean growth with good meat quality (Cameron et al., 1998). The reasons of negative relationships among growth performance and meat and eating quality traits are not completely clear. Increased rate of muscle growth can lead to changes in histochemical muscle properties such as an increase in the proportion of type IIB fibres which can result in less tender and less red meat (Warriss, 2000). In terms of a nutritional treatment, which can be beneficial to improving meat and eating quality, special attention in recent years has been paid to (CLA). Therefore, the aim of this study was to determine the influence of dietary CLA supplementation on histochemical profile of m. longissimus dorsi from pigs slaughter at heavier weights (129.9 kg).

Studies on growth promoter action can give an insight into the mechanisms of growth control. Calpain genes encode a family of proteins responsible for calcium-dependent proteolytic activity in mammalian cells. The ubiquitous enzymes µ- and m-calpain are activated in vitro by µM and mM calcium ion concentration, respectively. Both these calpain isoforms have been implicated in myofibrillar protein turnover and are regulated by calpastatin, a highly specific inhibitor protein. Overexpression of calpastatin has been strongly associated with skeletal muscle hypertrophy and meat toughness in livestock; a plausible mechanism has been that inhibition of calpain reduces myofibrillar protein degradation while protein synthesis continues unchanged in vivo, whilst inhibition of calpain post mortem prevents proteolytic cleavage of myofibrillar proteins. In pigs there are at least three calpastatin promoters (1xa, 1xb, 1u) with transcription factor binding motifs potentially responsive to β-agonist and IGF-1/calcineurin–mediated signalling pathways (Parr et al., 2001). The objective of the current study is to compare the expression patterns of different calpastatin mRNA transcripts in pigs treated with two different classes of growth promoters: clenbuterol treatment for 24 h and porcine somatotropin (pST) for 7 d.

Although feeding pigs ad libitum is known to result in increased tenderness (e.g. MLC, 1989), there would be benefits in reduced cost of production if this could be obtained without the concomitant reduction in feed efficiency and carcass leanness. The ad libitum effect on tenderness could be due to higher lean tissue growth rate (LTGR) and associated increased protein turnover and muscle enzyme activity, but other factors may also contribute, such as reduced feeding stress compared to restricted feeding. The aim of this trial was to assess the eating quality of pork from pigs reared in a range of housing and nutritional treatments, designed to give a wide variation in LTGR.

In recent pig nutrition the use of fibre-rich feed ingredients is increasing. In general, utilisation of energy from fermentable non-starch polysaccharides (NSP) are considered to be approximately 70 % of the energetic efficiency of digestible starch. According to Schrama et al. (1998) growing pigs are able to use energy from highly fermentable NSP (sugar beet pulp silage) as efficient as energy from digestible starch from tapioca. However, an issue is risen whether the source of energy affects the pig performance and slaughter quality, and if the effect of energy sources are modified at different feeding levels. The aim of the present study is to compare the effect of highly fermentable NSP with starch and oil at two energy intakes on finishing and slaughter performance of pigs and pork quality.

The use of dietary fats and oils to manipulate the fatty acid profile in meat animals to produce higher quality, healthier meat has been well documented, for example by Enser, et al (2000). In Ghana and other developing countries, agro-industrial by products containing oil have been examined because they reduce feed costs. These include palm products and inclusion levels have been recommended (Okai, 1998). However, there is no information on the effect of these palm products on the fatty acid profile and the quality of pork and pork fat. The objective of this study was to evaluate the effects of palm and palm kernel oils on the fatty acid composition of pork fat and fat firmness.

Intensive production systems require that inputs and facilities be used in the most efficient manner. Stocking strategy can have a significant effect on the output from pig units. Crowding can result in depressed pig performance while understocking can cause reduced pigmeat output. Alternatively, split-marketing pigs on a number of days (SM) can result in lower within pen variation in pig weight and improved growth rate of pigs remaining behind. Two experiments were conducted to determine if performance of pigs and pigmeat output per unit area could be improved either by varying the stocking density (by increasing group size) or by engaging in split-marketing.