The Department of Health (1994) recommended people to reduce their intake of total fat and saturated fat and increase that of n -3 polyunsaturated fatty acids (PUFA) to 200 mg/d. The ratio of PUFA:saturated fatty acids (P:S ratio) in the total diet should be >0.4 with an n -6:n -3 ratio of <4. Since fish consumption, a major source of dietary long-chain n -3 PUFA, is low in the UK, research has focused on improving the fatty acid balance of other meats. The objective of this paper is to summarise studies by IGER and the University of Bristol on manipulating fatty acid composition of beef.

Ruminant meat products have a relatively saturated fatty acid profile so lipid oxidation during the postmortem period, which could lead to off-odours and flavours and trigger undesirable colour changes, is usually minor. However, attempts to increase levels of PUFA in meat for health reasons could be compromised by increased lipid oxidation. This paper is a summary of recently completed work between University of Bristol and IGER on the links between fatty acid composition and oxidative stability in beef and seeks to draw general conclusions.

Red clover silage is an important component of many organic dairy systems. The high intake and milk production potential of red clover silage has been recognised for many years (e.g. Thomas et al., 1985). Our earlier studies confirmed this potential and showed additional benefits with increased polyunsaturated fatty acid (PUFA) content of milk (Dewhurst et al., 2002). The objective of this study was to investigate further the effect of red clover silage on milk PUFA and to examine whether supplementary vitamin E, which is needed to slow oxidative deterioration of milk with enhanced PUFA content, had an effect.

Some studies with beef cattle have shown that breed and diet affect tissue fatty acid composition and meat quality (Choi et al., 2000; Scollan et al., 2001). However, the effects of breed are often confounded with differences in growth rate and body composition. Diet also affects fatty acid composition, however, feed composition studies are often confounded by the use of mixed diets and few have compared all-forage with all-concentrate diets. This study, therefore, was designed to compare Aberdeen Angus and Holstein-Friesian breeds growing at similar rates and fed either all-forage or a high concentrate diet.

To enable producers to meet market requirements for lamb carcasses from the resources available, it is important to know how breeds differ in growth and development over time and how this is affected by feeding regime. The aims of this study were to explore the effect of diverse breed and feed types on carcass composition, growth and feed intake and investigate how these change during growth.

In order for producers to meet market requirements for lamb carcasses from the resources available, they need to know how breeds differ in growth and development over time and how this is affected by feeding regime. A previous paper explored the effect of diverse breed and feed types on carcass composition, growth and feed intake. This paper uses different mathematical descriptions of growth to study the relationships between live weight and time and between live weight and cumulative feed intake.

Dynamic selection algorithms using quadratic indices to optimise the contributions of selection candidates for maximising rates of genetic gain (ΔG) while constraining the rate of inbreeding (ΔF) in the long-term to pre-defined values, are available (Grundy et al, 1998). Avendaño et al (2001 a,b) applied these optimal selection algorithms on the UK Meatlinc (sheep) and Aberdeen Angus (beef cattle) pedigree breeds and found substantial expected increases (of at least 17%) in the average index score at the observed ΔF. Although these algorithms constitute powerful operational tools for breeding schemes, the framework for deterministically predicting ΔG under optimal selection with restricted ΔF is not yet available. This study presents a novel approach to this problem.

National dairy records have shown that correlations between production and fertility are generally unfavourable. There has therefore been a genetic downward trend for fertility due to the increase selection pressure on yield and as a genetic problem it requires a genetic solution. The effect of sire genetics on daughter fertility is included in many genetic indices around the world. As part of a DEFRA LINK project to produce an UK fertility index this study estimates genetic parameters and sire predicted transmitting ability (PTAs) for fertility traits in the UK.

There is a dearth of information available on the effects of donor animal on the fermentative capacity of equine faecal inocula for use in in vitro digestibility determinations. Furthermore, there is little knowledge of the degradation characteristic of feedstuffs incubated with equine faecal inocula. As such this study aimed to elucidate the effect of donor animal on the fermentation of feedstuffs in vitro and to assess the in vitro degradation characteristics of three commonly fed components of horse diets incubated with equine faecal inocula.

Ruminal microbes play a important role in the fermentation of structural plant polysaccharides, and constitute a major source of protein for the animal. Dietary protein provides amino acids which generally stimulate microbial growth rates and yields. The aim of this experiment was to identify, using a deletion approach, which individual amino acids limit fermentation of one of the main components of plant fibre, xylan.

Maize silage consists of a starch and a fibrous fraction, both of which should be considered when assessing nutritive value. The in vitro evaluation of starch disappearance is laborious and costly. The near infrared reflectance spectroscopy (NIRS) technique requires limited sample preparation and is quick to operate once a calibration is established. This study investigated the potential of NIRS to predict maize starch disappearance in vitro.

Despite many promising characteristics as a low-input home-grown protein source, red clover (Cv) silage supplies deficient amounts of rumen available carbohydrates to allow an efficient use of the available forms of soluble N. An in vitro experiment was designed in order to determine the optimum rate of inclusion of a rumen degradable carbohydrate source to optimise rumen microbial N yield of Cv silage.

Up to now, genetic selection in cattle has been directed in favour of muscle growth, which changes muscle characteristics, and hence meat quality. One key concern, that now needs examination, is to understand the relationships between muscle growth and muscle characteristics related to meat quality. To achieve such a goal, muscles of divergently selected animals were analysed by three complementary approaches: (i) determination of muscle biochemical characteristics, (ii) identification of differentially expressed genes using transcriptomic and proteomic tools, (iii) identification of Single Nucleotide Polymorphisms (SNP) within candidate genes.

Apart from all the issues regarding health and undesirable recessive genes, which are determining factors to identify bulls not suitable for AI, there are other aspects which can be considered. The principal aims of AI studs are the selection of the best animals from a genetic point of view and the production of semen in a very short time, in order to start progeny testing as soon as possible. In Italy progeny testing starts when 1200 straws for each young bull are available. This requirement implies that bulls should be in good physical condition. According to this, the genetic centre of the Italian Holstein Breeder Association (ANAFI) has been paying growing attention to animal welfare and fitness, recording routinely some biometrical indicators. Body weight (BW), scrotal circumference (SC), body condition score (BCS) are some examples of this policy and could be helpful and easy predictors of reproductive performance for a young progeny testing dairy bull. The objective of this report was to conduct a preliminary analysis on the genetic aspects of BW, BCS, SC, age at the 1st usable straw (AGE1) and age at the 1200th straw (AGE1200) in Italian Holstein young bulls.

The coefficient of genetic variation of fertility traits is of a similar magnitude to that present in production traits, however traditional measurements of fertility have low heritability (h2 < 0.05), and recording is often poor, hindering the identification of genetically superior animals. The effect of sire on daughter fertility has been examined as part of a DEFRA LINK project to produce an UK fertility index. The project is investigating the use of six currently recorded traits to calculate sire genetic merit for fertility: calving interval (CI), interval to first service (DIMFIR), nonreturn rate 56 (NR56), number of services per conception (CINSOBS), milk yield and condition score (Wall et al., 2002). An alternative way to measure fertility is to use endocrine measurements such as interval to commencement of luteal activity postpartum (CLA). This parameter is less influenced by management decisions and has a moderate heritability (0.16; Royal et al., 2002a.) and is measurable early in lactation. Although information on the genetic relationships between CLA and other traits of economic importance have been reported previously (Royal et al., 2002a.; Royal et al, 2002b.) further information would be useful in order to assess the usefulness of incorporating CLA into a future UK breeding programme. The objective of these analyses was therefore to obtain information on the genetic correlation (rA) between lnCLA and the emerging UK national fertility proofs.

Interest is accruing in indicator traits as predictors of fertility which: 1) can be more easily recorded; 2) can be measured early in life; and, 3) possess a co-heritability that is larger than the heritability of the fertility traits. Potentially interesting indicator traits include body condition score (BCS) and body weight (BW). The objective of this study was to estimate genetic (co) variances between BCS, BCS change, BW, BW change, and fertility traits in dairy cattle.

There is growing interest in the dairy industry to broaden breeding objectives by incorporating health and welfare traits into selection indices. Although these traits are difficult to measure directly, there is good evidence to show that some linear type traits are genetically correlated with certain health and welfare traits, e.g. udder-type with somatic cell count (Mrode, Swanson and Lindberg, 1999) and locomotion with lameness (Boelling, 1996). Linear and composite type traits, such as locomotion and the feet and legs and mammary system composites, have been proposed for inclusion in a future modification to the UK Profitable Life Index (PLI). The objective of this study was to estimate genetic parameters of locomotion and composite traits for application in UK national dairy genetic evaluations for Jerseys and Guernseys.

Pre-1990 published responses to supplementation at pasture ranged from 0.4 to 0.6kg milk/kg concentrate fed. However since 1990 higher responses to concentrate supplementation at pasture have been published (Delaby 2001). The objective of this study was to determine if milk production responses of Holstein-Friesian dairy cows to concentrate supplementation at pasture are influenced by genetic merit (milk yield potential) in a spring calving grass based system of milk production.

In recent years the relevance of continued selection for higher milk yield alone has been questioned for three reasons (Simm, 1998): 1) the introduction of milk quotas in some countries, 2) the now well documented deleterious effect of selection for yield on health and fertility (Pryce and Veerkamp, 2001), and, 3) the increased emphasis in payment schemes in many countries on milk composition. The purpose of this study was to measure the biological efficiency of two dual-purpose breeds (Montbeliarde (MB) and Normande (NR)) relative to two Holstein-Friesian strains (upgraded Irish Holstein-Friesian (CL) and Dutch Holstein-Friesian (HF)) on a spring-calving milk production system based mainly on grazed grass as a feed.

Nutrition of ewes during late pregnancy is a key factor influencing lamb survival and subsequent lamb growth and performance. Results from on-farm trials indicate that the superior lamb output from highly prolific compared with moderately prolific ewe breed types is less in grass-based compared with indoor lambing systems (Carson and Dawson, 2002). This is as a result of higher mortality rates of triplet lambs in outdoor systems with lower levels of intervention. Feeding and management strategies to maximise lamb viability for multiple births are required for grass-based lambing systems. Protein nutrition is likely to be a key factor, particularly considering that energy intakes in late pregnancy in triplet-bearing ewes are unlikely to meet requirements (Robinson, 1983). At sub-optimal energy intakes the supply of rumen undegraded protein is a major determinant of colostrum production and lamb birth weight. The objectives of this experiment were to investigate the effect of supplementing grass-based diets with concentrates with a range of digestible undegradable protein concentrations on colostrum production and lamb output.