In previous studies where sheep were subjected to experimental subclinical Trichostrongylus colubriformis infections, protein metabolism was seriously impaired during both the initial infection (5-7 weeks at early dosing) and the subsequent immune response (11-13 weeks of dosing) periods (see MacRae, 1993). Symonds and Jones (1983) reported that T. colubriformis infection increased the rates of protein synthesis in the small and large intestines of guinea pigs by 24 and 70% respectively, however there are no equivalent data in farm animals. In the present study trans-organ catheterisation procedures have been coupled with mass isotope tracer kinetics to examine leucine metabolism across the gastrointestinal (g.i.) tract of lambs subjected to subclinical T. colubriformis infection.

It is known that feeding frequency affects the insulin status of lactating ruminants (Sutton et al, 1988), and that this may influence milk composition. It is unclear, however, whether these effects are due to modulation of mammary metabolism, or regulation of substrate distribution. The present study aimed to establish whether the partition of blood flow to the mammary gland is responsive to insulin and nutritional status.

The mammary gland of lactating ruminants (Guinard & Rulquin 1994) does not appear to extract sufficient quantities of free amino acids (AA) to account for their output as milk protein. Based upon application of a precursor (blood or plasma free AA):product (casein) labelling technique (Backwell et al. 1996) in goats, results suggest that blood peptides or proteins taken up by the gland probably account for this deficit. However, the deficiency appears to be alleviated when supplemental protein or AA are infused (Guinard & Rulquin 1994), suggesting that uptake of peptide bound AA is reduced while that of the free AA is increased. The objective of the current study was to corroborate these findings, thus the precursonproduct labelling technique was applied in lactating goats to determine whether arterial free phenylalanine supply affects the contribution of peptide bound phenylalanine and tyrosine to casein synthesis and compare the results to the net uptake (NU) method.

Genetic selection has greatly improved individual cow productivity. A high genetic merit Holstein Friesian cow will produce 10,000 of litres of milk in a 305 day lactation, those of lower genetic merit half this amount. Despite major research effort in generating these differences, quantitative biological description of what has been achieved is lacking. The aim of this study was to compare biological variables of relevance to milk synthesis in well defined high genetic merit and lower genetic merit dairy cows.

12 cows of high genetic merit (HGM: top 5% of UK national herd) and 12 of lower genetic merit (LGM: close to UK average) were purchased from the Blythbank and Langhill herds; the ontogeny of these selection lines has been described elsewhere (Woolliams et al, 1993). Mean parity was 3.7±0.3 and was balanced between HGM and LGM. Management of the two groups was identical. Measurements were made over a period of two weeks close to peak lactation. Milk yield was recorded at each milking. Plasma samples were collected and analysed for a variety of hormones by radioimmunoassay and metabolites by established spectrophotometric assays. Udder size was determined by a casting technique (Dewhurst et al., 1993) and mammary biopsies for key enzyme activities were obtained as described by Knight et. al. (1992). Differences between lines were analysed by analysis of variance (ANOVA).

Qualitative assessment of behaviour is based upon the integration by the observer of many pieces of information which in conventional quantitative approaches are recorded separately. Behaviour is for example summed up as ‘fearful’, ‘anxious’ or ‘distressed’. Such interpretations form the core of the lay public's concern for animal suffering, and therefore are frequently dismissed as ‘anthropomorphic’ and unscientific. However, in theory it is possible that such assessments reflect observable aspects of behavioural organization, and may be liable to scientific analysis. A first step in considering this hypothesis is to investigate the interobserver reliability of qualitative assessments. The aim of this study was to determine the extent to which untrained observers show agreement in their spontaneous qualitative descriptions of interactive behaviour in growing pigs.

The introduction of electronic feeders has allowed accurate measures of individual feed intake in a group housing system, similar to that in the production environment. These feeders also provide other feeding pattern information, such as how many meals are taken each day and how big they are, which could be of use to further improve the accuracy of selection for feed conversion ratio and growth traits. The main aims of this study were to predict the increase in genetic gain achieved by including feed intake and feeding pattern traits as selection criteria.

DNA-based markers and genetic maps of major livestock species have been developed in the last few years. These, together with experimental populations and appropriate statistical methods, provide the tools to dissect causes of economically important genetic variation in livestock. A cross between genetically diverse lines is a powerful experimental design for such a study. In an F2 or backcross population from such a cross, markers are likely to be highly informative and the genes that control the differences between the lines will be segregating. We have been developing such a resource population based on a cross between the British Large White and Chinese Meishan pigs. These breeds differ for many traits, with the Meishan being inferior for growth rate and fatness, but superior for reproduction traits. Here we report the mapping of major genetic effects on growth rate and fatness in our cross.

The ingestion of creep feed by piglets depends upon them displaying suitable exploratory behaviours away from the sows udder. However, sows milk has an excellent FCR and it may be argued that, where the udder is available, exploration away from it is a failure to optimise the use of available food resources. A corrolary to this is that those piglets displaying exploratory behaviour away from the sows udder will be those piglets for which further udder massage shows no net gain i.e. those exploiting the maximum potential of the udder and those for whom the udder shows very little benefit. The former group will be characterised by heavier weights and faster growth rates. The latter group will be characterised by lighter weights and slower growth rates. It may be assumed that animals exist on a continuum between these two states. In commercial conditions the latter group is typically fostered off or culled. This project tested the hypothesis that, in healthy litters (thus excluding the latter group), exploratory behaviour away from the udder will be displayed proportional to the weight of the piglet.

There are marked differences between heifers, 2nd parity and older cows in their lactation curves, even when they are offered high quality rations ad libitum. These differences indicate different energy requirements, and thus should be taken into account when formulating rations for the different parities. The objective of this study was to quantify how the pattern of milk production relative to time from calving is affected by parity for incorporation into energy requirement predictions.

The accurate prediction of lactation yield for a dairy cow has been a long standing goal for improving management. Historically the approach has been to assume that yield as a function of time follows a lactation curve which can be assigned a form that applies to all cows, and that cows differ in the parameters of this common curve. This has led to a plethora of forms being suggested for this common curve, of which perhaps the most well-known is that of Wood(1967). The biggest problem with this approach is the assumption that all cows and all management systems combine to produce individual lactations described by a single form of ‘lactation curve’. A novel approach using mixed-model smoothing was investigated in this study which: (i) fits a shape of lactation, assuming no specific parametric form , to daily yield records of a group of cows by using a patterned (co)variance matrix to describe deviations from a linear trend for time postpartum in a mixed model; and (ii) allows individual yields to be predicted using this ‘mean’ curve and the deviation of an individual's yield record from this mean.

In a mastitic event damage to the epithelial tissue of the mammary gland, and in particular an increase in paracellular permeability allows sodium to enter the milk from the blood (Schaar and Funke, 1986). Normally there is a stepwise gradient of declining sodium concentration from the interstitial fluid to the epithelial cells to the milk (Berga and Neville, 1985). Milk potassium content is reduced in milk of cows with mastitis, but the proportional change is less than that of sodium (Wegner and Stull, 1978). An experiment was conducted to investigate the response of three mastitis pathogens to the changes in sodium and potassium concentrations in their growth media that are typical of the changes occurring during a mastitic event.

Lameness is a major cause of lost production, economic loss and compromised welfare in dairy cows. The majority of bovine lameness results from damage to the hoof, culminating in solear lesions and inflammation of the laminae (laminitis). Management factors predisposing to laminitis have been identified, but little is known about the biology of hoof development. Impaired keratinization has been linked histologically with subsequent laminitis, but factors regulating keratinization are unknown. We have developed a tissue culture technique for measuring cell proliferation and keratinization in hoof explants obtained by biopsy.

Whilst current rationing systems are used to calculate the metabolisable energy (ME) requirements of dairy cows producing more than 50kg milk/day, the extent to which the digestive efficiency of the cow may be compromised at high intake levels has not been established. Equally the effect of a sustained energy deficit on milk composition is not known whilst the extent of energy contribution from mobilised tissue has not been quantified. This study was designed to examine energy metabolism in high yielding cows offered ad libitum total mixed ration during early/mid lactation.

Body composition of animals may change (a) in response to treatments or (b) as they grow older. Studies on (a) generally model each component of composition separately, without the constraint that predicted components sum to 1 (e.g. Keane et al 1990). Allometric regression is widely used in studies of growth and differentiation (change in component proportions). This frequently involves estimating the parameters of a linear relation between the logarithm of weight of an organ or part (Wi) and the logarithm of the weight of the whole animal (w). Sometimes the relation is between an organ and a part of the animal that contains the organ as a subcomponent. A similar difficulty as in (a) arises here also. The allometric regression equations can be recast to give predictive models for the composition of the animal at different weights. In this form the model is

As far as consumers are concerned, the major quality characteristics of beef meat are an attracting color and tenderness (Smulders et al., 1991). The chemical composition - protein, fat and fatty acids contents mainly - is of importance for the dietitian. These parameters are influenced to a large extent by the management - diet and environment - of the fattening animals. The aim of the present paper is to relate some parameters of meat quality and meat composition with animal performance in growing fattening bulls.

The calpain enzyme system plays an important role in the proteolytic events leading to the conversion of muscle to meat in livestock species. Evidence in beef has shown that the levels of calpastatin, the inhibitory component of the system, measured 24 h after slaughter can be used to predict the degree of tenderisation achieved at the end of the normal conditioning period (Koohmaraie et al., 1995). Recent experimental work in pig muscle has shown that calpastatin can be increased by protocols which mimic stress and that these increases relate to changes in tenderness (Sensky et al., 1996; Sensky et al., 1997). In this study differences in the calpain system in randomly selected pigs slaughtered at a commercial slaughterhouse were investigated, with respect to the degree to which the meat tenderised.

Information on the responses in meat and eating quality to selection for components of lean growth rate is important to the British pig breeding industry when evaluating alternative selection strategies. The current study determined responses in meat and eating quality traits to selection for components of lean growth rate.

Continued improvements in lamb carcass quality are important to the successful development of the UK sheep industry. A previous study at this Institute has shown that 50% Texel or Rouge de l'Ouest genes can be included in a traditional lowland crossbred ewe type without reducing lamb output. This present study was designed to provide information on the effects of using these continental genes in ewes on lamb carcass quality.

Sinclair et al. (1993) found that a diet formulated to be synchronous with regard to hourly release of nitrogen and energy increased microbial protein synthesis by 14% in sheep. Dairy cows in early lactation experience a shortfall of energy and protein, with available protein determining the overall efficiency of metabolism (MacRae and Lobley, 1986) and subsequent milk production. It is therefore necessary to maximise microbial protein yield during this period. In this study diets were designed for lactating dairy cows to contain the same feed ingredients, but to release nitrogen and energy in the rumen at different times. Rumen fermentation parameters, nutrient flows to the small intestine and production performance were investigated.

Previous work (Metcalf et al 1996) has suggested that, even for cows when ME and MP supplies were balanced, the relationship between MP intake and net protein output at higher levels of feeding and production differs from that assumed in the MP system. This experiment was designed to test the concept that the efficiency of MP use for milk protein secretion is limited when metabolisable energy (ME) is limiting.