Wheat and wheat by-products vary in their available energy and protein content (Batterham et al., 1980) leading to unpredictable growth rate and feed use efficiency. Carbohydrase enzymes, targeting the non-starch polysaccharides in these raw materials, may improve their nutrient availability. However, questions remain over the relationship between the quality of the dietary raw materials and the level of exogenous enzyme activity required in the feed to elicit a response from pigs. Hence, the response of pigs to the use of a fungal xylanase, produced by Trichoderma longibrachiatum, was studied in diets containing wheat and wheat by-products.

Leptin is synthesised and secreted from adipocytes into the blood stream and transported to the brain, where it acts to cause a release of factors which can reduce food intake (Houseknecht et al., 1998). There are two murine mutations of the recessive gene coding for leptin which are associated with obesity. The Lepob allele determines synthesis and secretion of leptin, while the Lepdb allele determines responsiveness to leptin. In the Edinburgh lean growth experiment in pigs, selection for high and low daily food intake (DFI) has been practiced for seven generations in a Large White herd, which provides the experimental resource to determine if the correlated response in fat deposition is consistent with insufficient leptin production or with insensitivity to leptin.

Currently there are two theoretical frameworks for the prediction of feed intake of animals. The first considers feed intake to be a consequence of the animal eating to achieve its genetic potential (Kyriazakis and Emmans, 1999). When potential performance is not achieved it is because feed intake is being constrained, for example through the bulkiness of the feed or the hotness of the environment. The second framework considers feed intake to be an outcome of some process of optimisation so that intake is that which allows the maximisation of biological efficiency (Tolkamp and Ketelaars, 1992). The two frameworks differ in their predictions of the effect of temperature on the intake of bulky feeds. In the first, feed intake on bulky feeds is seen as a function of the type of feed; in the second, feed intake is a function of both the type of feed and the environment. The first framework predicts that in the cold the intake of low, but not high, bulk feeds will increase. The second framework predicts that in the cold intake will be increased regardless of the type of feed offered. This experiment was designed to provide a severe test of the two feed intake theories.

The in vitro gas production technique is a means of measuring the dynamics of fermentation. It is related to short chain fatty acid (SCFA) production, and so could be used to estimate ATP supply for rumen microorganisms. However, different fermentation patterns produce different amounts of gas. No fermentation gas is associated with the production of propionate, and so an increase in the proportion of propionic: (acetic+butyric) (P:AB) would be associated with a decrease in the volume of gas produced. If the molar proportions of SCFA changed during a fermentation, then this would complicate the interpretation of the gas production profile (GPP). If the GPP, combined with a measure of SCFA concentrations at the end of the incubation, was used to estimate ATP yield during the incubation, then changes in P:AB during the incubation may affect these estimates. The objectives of this experiment were therefore to determine whether P:AB did change during an in vitro incubation, and whether any such change affected the accuracy of the prediction of ATP yield with time.

Rumen micro-organisms ferment feeds to short chain fatty acids (SCFA) with the production of ATP. Measuring SCFA concentration in vitro could therefore be used to predict the yield of ATP in vitro. This estimate could then be used to predict the yield of synthesised microbial biomass. However, feeds may interact when they are incubated together, and so it is quite possible that ATP yield is not additive. The objectives of this experiment were therefore to determine whether the yield of total SCFA produced by feed mixtures was additive, and also whether the ATP yield of feed mixtures could be predicted from the calculated ATP yield of the individual feeds.

The in situ measurement of rumen degradability explains properly the disappearance of rumen feeds by solubilization. However, this methodology does not assure wheather the material in the rumen indeed suffered microbial degradation, or if the loss of material occurred by other reasons. The in vitro gas production technique, on other hand, measures a product of the fermentation process. If the remains of the gas production is recovered at pre-determined intervals, we could also determine the rate and extent of the degradation occurred in the process. Thus, the aim of this work was to compare the rate and extent of the degradation obtained from these two methodologies.

Several techniques involving enzymes as alternatives to rumen fluid in in vitro studies have been proposed. However, high cost, ill-defined characterisation and high variation among enzyme preparations and batches have discouraged their use. In addition, most studies have aimed at determining dry matter degradability (DMD) at a fixed time, commonly 48 h. Consequently little information has been published concerning the DM degradation dynamics of forages incubated with enzymes. Therefore the objective of the present study was to compare the ability of a commercial enzyme mixture to describe the fermentation dynamics of two contrasting forages, using the ANKOM in vitro fermentation system (Daisy II, ANKOM Co, USA).

The effect of rearing or finishing beef cattle on fully slatted floors on their welfare has recently been questioned. The objective of this experiment was to examine the effects of using different types of floors in accommodation for beef cattle on their performance and behaviour.

In humans subliminal perception is more evident in vision than other senses (Dixon, 1987) but it has not been reported in animals. The presence of subliminal visual perception might be suspected in cattle because of their low level of perceptual discrimination ability of visual cues relative to humans (e.g. Phillips and Weiguo, 1991), despite their sensory apparatus being similar in many respects. Experiments were therefore conducted to determine the extent of cattle colour perception and examine whether the effects of colour on cattle behaviour transcend that their perceptual abilities. We sought to a) confirm that cattle are dichromats, taking account of stimulus brightness, which has not always been the case in previous experiments investigating cattle colour vision, and b) investigate whether cattle exhibit differences in behaviour in isoluminant primary colours for trichromatic vision. Confirmation that cattle are dichromats, together with demonstrations of differences in behaviour in the three primary colours would suggest the existence of subliminal perception, and would question the validity of determining animal welfare requirements solely on psychophysical testing of supraliminal perception.

Current commercial dairy practice involves the removal of the calf from the dam within the first two days of life. This early separation may result in stress for both cow and calf. However, it may also be that separation occurs before the cow-calf bond is established. The aim of this study was to determine if cows and calves respond to each other's calls after separation and whether they could distinguish their own calf's or dam's calls from another calf's or cow's calls.

Most indoor sows in Denmark and the UK continue to farrow in crates. Before farrowing, sows are highly motivated to nest-build and gilts farrowing in crates without straw have an especially large stress response over the nest-building period (Jarvis et al., 1997). In non-crated sows, the inability to nest-build affects the subsequent maternal behaviour of the sow after farrowing (Herskin et al., 1999). This study aimed to determine whether supplying straw before farrowing increased the anti-crushing and anti-predator behaviour of the crated sow after farrowing and improved piglet survival.

The mixing of unfamiliar sows at weaning forces the establishment of dominance hierarchies, which frequently involves aggression (Kay et al, 1999). The objective of this study was to determine whether different stocking densities and pen shapes would reduce the incidence of aggression and levels of skin damage. The ultimate aim was to design a mixing pen which could be used to enhance the welfare of groups of newly-weaned sows.

It has been proposed that the occurrence of the periparturient relaxation in immunity (PPRI) to gastrointestinal parasites is due to a lower partial priority of nutrient allocation to the immune functions, rather than to the reproductive functions, when parasitized hosts are offered scarce nutrient resources (Coop and Kyriazakis, 1999). This implies that immune functions directed towards gastrointestinal parasites will benefit from an increased supply from scarce resources, such as metabolizable protein (MP) and metabolizable energy (ME). In this experiment we studied whether the resistance in parasitized pregnant sheep is affected by an increased supply of MP, or ME, or both.

A nutrient partitioning framework has been developed to account for host nutrition-parasite interactions in mammals (Coop and Kyriazakis, 1999). The framework puts forward a nutritional basis for the occurrence of the periparturient relaxation of immunity (PPRI) to gastrointestinal parasites in sheep. The PPRI would be expected to occur because it is proposed that the reproductive effort has a higher partial priority than the immune functions when hosts are given access to scarce nutrient resources, such as metabolizable protein (MP). This would imply that i) immune functions towards parasites will benefit from an increased MP supply, and that ii) the degree of the PPRI depends on the level of reproductive effort. We studied these predictions by comparing performance and resistance in parasitized twin- and single-rearing ewes, which were offered increasing amounts of MP.

Parasitised sheep consuming forages high in condensed tannins (CT) show lower faecal egg counts (FEC) and total worm burden (TWB) compared to those consuming CT free forages (Niezen et al., 1998). This may be due to an indirect effect of CT, through an increase in protein availability; extra protein could improve the host’s ability to mount an effective response towards gastrointestinal parasites, during the expression of the immunity (Coop and Kyriazakis, 1999). However, CT have been also shown to have a direct anthelmintic effect on adult Trichostrongylus colubriformis (intestinal nematode), when they were administered for a short period (Athanasiadou et al., 2000). The objectives of this experiment were i) to elucidate the effects of a continuous intake of CT during the development of a T.colubriformis infection and ii) to test whether these effects are dose dependent.

The transition period of the dairy cow is physiologically and nutritionally stressful, particularly as feed intake is reduced and nutrient demands for foetal growth and initiation of milk synthesis are increased. It has been suggested that feeding concentrates in late gestation promotes the development of ruminal papillae, which takes 4 to 6 weeks to fully develop, consequently resulting in improved absorption of volatile fatty acids and increased food intake during early lactation. A recent study undertaken at this Institute (Keady et al. 1999) concluded that relative to silage offered ad libitum as the sole diet supplementation with 5 kg of concentrate during the last 28 days of gestation increased milk fat by 1.5 g/kg and improved milk yield by 0.6 kg/day during the first 12 weeks of the subsequent lactation. The response to dry cow supplementation reported by Keady et al. (1999) could have been mediated either by increased nutrient intake or by changes in the forage to concentrate ratio of the diet during the dry period. The present study was undertaken to evaluate the effect of level of energy intake and source of nutrients in late gestation on subsequent milk yield and composition.

Genetic improvement is permanent and cumulative. Improvements made in one generation are passed onto the next. In the UK two selection indexes are currently available to the dairy industry, they are PIN (Profit Index; production only) and £PLI (Profitable Lifetime Index; production plus lifespan). Much of the current and anticipated index research and development will be on broader breeding goals that include health and fertility traits. Economic responses expected for PIN and £PLI over a 20 year period were calculated in addition to a hypothetical index where it was assumed that PTAs (predicted transmitting abilities) for mastitis (M) and calving interval (CI) were available (£PLI+M+CI).

Genetic evaluations for milk production traits in dairy cattle based on test day yields (TD) have generated much interest recently due to a number of advantages, including improved accuracy of predicting breeding values and estimation of persistency evaluations. One of the methods proposed for a test day evaluation system is the random regression model (RRM) approach fitting covariance functions such as the Legendre Polynomials. Preliminary genetic evaluations using this approach have been produced by the Animal Data Centre in the United Kingdom based on the research of Brotherstone et al (1999). The objective of this paper is to estimate relative weights on pedigree and TD in evaluations of cows using RRM fitting Legendre Polynomials and compare with 305-day yield evaluations. Secondly to examine the efficiency of using part lactation TD information to predict breeding values for cows.

Profitability of sheep production systems depends on several different animal characteristics rather than a single trait. Economic selection indexes combine information from more than one trait into an overall score, to maximise genetic gain. Economic values (EVs) are required for each trait in the breeding goal so that selection emphasis is proportional to the economic importance of each trait. Defining clear breeding goals is more complex for hill breeds than for other sectors of the sheep industry because they provide breeding females in addition to lambs for slaughter. The aims of this paper are to i) describe how EVs for breeding goal traits suitable for UK hill sheep were derived for a combination of carcass, maternal and ‘sustainability’ traits using a bio-economic model, and ii) show how these EVs vary between different production systems as a result of the differences in the physical constraints of farm size, pasture availability and the biological limits of sheep in extensive rearing environments.

Many traits that are of interest to breeders, such as food intake, are expressed continuously during the life of an animal and the individual's phenotype will change with age. Traditional genetic analysis of these traits has treated as them as discrete traits, ignoring the correlations among records at different ages. Recently methods have been developed to overcome this deficiency and allow an infinite dimensional approach, which can provide more accurate estimates of genetic and phenotypic parameters (Kirkpatrick et al. 1994, Meyer and Hill 1997). The aim of this study was to investigate the effect of stage of growth on the genetic and phenotypic parameter estimates of daily food intake.