The effect of pregnancy on milk yield and composition has long been recognised (Erb, 1952), yet it is not currently directly accounted for in genetic evaluations. In the UK, total lactation yields are adjusted for the effect of calving interval (CI) with adjustment factors (Brotherstone, 1987) which assume a constant effect across gestation stage (GS). The effect of pregnancy however varies with gestation stage (Coulon, 1995) and is different from the effect of CI. In genetic evaluation based on test day models, it is essential to account for the direct effect of pregnancy specific to individual records. The objective of this study was to estimate the effect of gestation stage on daily milk yield and its components in first lactation.

High producing dairy cows have been found to be more susceptible to disease (Jones et al., 1994; Göhn et al., 1995) raising concerns about the welfare of the modern dairy cow. Genotype and number of lactations may affect various health problems differently, and their relative importance may vary. The categorical nature and low incidence of health events necessitates large data-sets, but the use of data collected across herds may introduce unwanted variation. Analysis of a comprehensive data-set from a single herd was carried out to investigate the effects of genetic line and lactation number on the incidence of various health and reproductive problems.

In many countries there has been an interest in including measures of liveweight and/or size in dairy cattle breeding goals, with the main aim of decreasing food costs. Whilst opinions about the right size of a dairy cow seem to differ among countries, it has been argued that because of the strong associations between liveweight, intake(-capacity) and condition score, the whole complex of these traits should be considered simultaneously (Veerkamp 1996). To do so, genetic parameters (and economic values) are required. Hence, the objective of this study is to estimate genetic parameters for yield, food intake, liveweight and condition score in first lactation heifers.

The use of Embryo Transfer (ET) in HF cattle breeding is now a routine technique. It provides an opportunity to increase the contribution of the dam to genetic progress in the population. The aim of this paper is to characterise the cows chosen as embryo donors, and to detect any changes in donor characteristics.

The Japanese black cattle (Wagyu) is well known for their high marbling and price meat. Usually purebred calves from Japanese black cattle are used for the station or field progeny testing. If genetic variance of particular traits of the dam breed is much smaller than that of the sire breed, breeding values of sires can be estimated accurately from their crossbred progeny because genetic difference among dams is relatively small and can be ignored. The objective of this study was to investigate the possibility of using crossbred for progeny testing of Japanese black sires. Since marbling scores or carcass prices of Holstein cattle are low and do not vary widely, crossbred between Japanese black and Holstein was chosen in this study.

Anthropogenic activities have lead to a redistribution of heavy metals within the environment, often with the effect of increasing the concentration in which they are found within farming ecosystems. This series of trials was conducted to determine whether farm animals could detect heavy metals in feeds, if so at what levels, and whether they preferred uncontaminated feeds. Both toxic and non-toxic metals were tested, but toxic metals were only tested at levels that would not induce clinical problems.

Anthropogenic lead is the most common cause of poisoning in ruminants. Vehicular lead emissions pollute herbage by the road, which may pose a risk to grazing ruminants. A series of experiments was conducted first to determine whether livestock could detect lead in herbage, and if so at what levels, and second whether they avoided lead contaminated herbage. The effects on grazing behaviour were recorded to investigate whether cattle could alter their grazing strategy to reduce their intake of lead from contaminated pasture.

Anthropogenic cadmium is increasing the cadmium concentration in herbage consumed by ruminants. It is derived mainly from phosphate fertilisers and mineral mixes added to concentrates, but in future sewage sludge applications to pasture may be more important. It has the potential to damage the health of the ruminants and ultimately the humans that consume their contaminated products, in particular offal. Cadmium is initially complexed by metalloproteins in the liver, extracted from the blood by the kidney and excreted in urine. In severe cases it impairs the reabsorption capabilities of the proximal tubules of the kidney. Although many clinical studies have been conducted with provocative levels of cadmium fed to laboratory animals, little is known about the potential for typical levels of cadmium in mildly contaminated feed to cause kidney damage in sheep.

Hill and Wilkinson (1997) found that the mean intake of soil+sludge DM by lambs grazing perennial ryegrass was 101g/kg total DM intake and Wilkinson et al (1996) observed accumulation of Pb in liver and kidney, but not in muscle tissue of housed lambs given grass diets containing 100 g/kg DM of soil mixed with sewage sludge and 900 g/kg DM dried grass. The aim of the trial was to assess the extent to which PTEs might accumulate in body tissues of lambs grazing grassland to which sludge had been applied over many years and where the soil contained concentrations of Cd which were close to the UK statutory limit for sludge-amended soil (3 mg/kg DM sampled to 25 cm depth; SI, 1989).

Disposal of sewage sludge to grassland is likely to increase in future years as a result of legislation to control disposal to the sea (CEC, 1991) and increased production (DoE, 1993). Recent research has investigated the possible accumulation of potentially toxic elements in body tissues of lambs given diets containing known amounts of sludge (Wilkinson et al, 1996). The aim of this experiment was to study the effects of season and method of application of sludge to grassland on voluntary feed intake, digestibility and growth of lambs.

The commercial rearing of llamas in the UK is of increasing interest but there is little information on their trace element status especially regarding copper metabolism. Previous work on a closely related species, the Alpaca (Lama pacos) has shown them to utilise copper less efficiently than sheep (Grace et al., 1994). As llamas are grazed on marginal or improved pastures they may become susceptible to copper deficiency (thiomolybdate toxicity). However, evidence also shows that llamas can suffer from copper toxicity (Junge and Thornburg, 1989). Therefore diagnosis of trace element status is needed prior to nutritional supplementation.

Trace element deficiencies are common in many countries and affect animal health, productivity and welfare. Trace elements that can be limiting in animal nutrition include copper, cobalt, selenium and zinc. Deficiency diseases may be manifested as a consequence of a single or a multiple element deficiency. Deficiency in any of the above trace elements can result in an increased disease susceptibility and a decreased immune function. A soluble glass bolus has been developed for the sustained release of zinc, cobalt and selenium to sheep, using the same technology as the commercially available copper, cobalt and selenium bolus (Cosecure). The aim of this experiment was to observe whether the trace elements released from the bolus would have an effect on the immune function of sheep, as measured by the humoral immune response to a novel antigen.

A sustained-release rumen bolus system (‘Small-Trace’, Agrimin Ltd., Brigg DN20 0SP) consisting of two polymer-coated cylinders (55mm length, 18mm diam) containing a compressed mixture of normal inorganic trace elements and vitamins had been demonstrated to be an effective long-term copper and selenium supplement for calves > c. 70kg liveweight (Hemingway et al. 1996). A modification of the calf bolus system appropriate for ewes is described using a single bolus together with an inert grinder to promote bolus matrix erosion/dissolution in the reticulum/rumen.

The standard recommendation for grazing cows to be given 60g calcined magnesite (c. 30 g Mg /day) seems large relative to the ARC (1980) dietary Mg allowance (0.17 coefficient of Mg absorption in the whole diet) of 32.6 g for 30 kg/day milk yield. ARC (1980) estimated the coefficient of absorption of calcined magnesite could be 0.05-0.10 and indicated that supplementary magnesium sources should be readily soluble in rumen liquor. Both temperature of calcination and particle size markedly influence rumen solubility and apparent Mg availability of calcined magnesite (Adam et al. 1996). Magnesium hydroxide powder (H, 404 g Mg/kg) is very finely divided (970 g/kg < 20 μm of which 870 g/kg is < 6um and with 200 g/kg < l μm diameter and is manufactured on a large scale (Redland Minerals, Hartlepool TS24 0BY). ‘Granular’ calcined magnesites are screened to < c. 2000μm diam.

The accumulation of copper (Cu) in the liver of intensively fed sheep, resulting in sub-clinical organ damage and eventually death due to Cu poisoning, is an important constraint on intensive animal production. Previous studies have demonstrated the antagonistic effect of dietary molybdenum (Mo) on Cu absorption in the ruminant (Suttle, 1991). The role of rumen ciliate protozoa in the breakdown of soluble protein and liberation of sulphide, also a Cu antagonist, and the reporting of a number of cases of chronic Cu poisoning in defaunated animals suggests that the state of the rumen microbial population may also have an effect on the absorption of dietary Cu. The aim of this experiment was to assess the effect of adding Mo to the diet and the availability of straw bedding, (through its effect on rumen environment and microbial population), on the liver Cu concentration at slaughter of early weaned lambs finished intensively on an all concentrate diet.

Feeding management in grazing systems usually involves supplementary feeding during critical periods to increase the intake and prevent high losses of body reserves (Gunn et al., 1992; Castro et al., 1994). However, in grazing systems the response to additional fed can be erratic or inconsistent at medium or long terms. Therefore it is necessary a better understanding of the effects of supplementation to define feeding strategies. The present experiment was designed to examine the effect of supplementation of grazing ewes during two consecutive production cycles on animal performance.

May lambing is attracting significant interest as a low input production method on UK farms but one major constraint to its uptake is a reduction in lamb output of around 20%. This is likely to be associated with adverse nutritional effects at grazing in December when nutrient intake is reduced by low sward quality and availability and weather effects. Supplementary feeding using feed blocks offers a method of improving nutrient intake which has been effective at improving reproductive performance in spring lambing hill flocks (Marsh and McCracken 1995).

Recent research has demonstrated that supplementary sodium enhances the magnesium status of cattle fed fresh herbage by limiting the antagonism of potassium to magnesium absorption in the rumen (Chiy and Phillips, 1993). This may explain the observed reduction in the somatic cell concentration in the milk of grazing dairy cows when they are offered a sodium supplement (Phillips et al. 1996). Magnesium has been recognised as the main macroelement affecting immunocompetence in laboratory animals (Miller, 1985), and it is likely that it is important for grazing ruminants, which are prone to hypermagnesaemia. It is unclear whether sodium supplements would be beneficial to cattle fed conserved feeds, where hypomagnesaemia is less common.

Ayrshire is one of the most important dairying areas in Scotland There is very little information for the phosphorus (P), magnesium (Mg) and copper (Cu) concentrations in grazed herbage over the whole season

The lack of vitamins in ruminants, might impair normal metabolic growth and reproductive functions. Borderline vitamin deficiency might be manifested as impaired fertility before clinical symptoms appear. Specific vitamin requirements for normal reproduction are not suggested for dairy cow nutrition. Vitamin loss in the rumen occur through engulfment, oxidation and degradation by the rumen bacteria. Vitamin A is extensively degraded in the rumen, and up to 50% of vitamin E does not reach the small intestine (Shin and Owens, 1990). The aim of this work was to evaluate the rumen disappearance and the intestinal digestibility of conventional and rumen protected (RP) vitamin A and E.