Ensilage of grass exposes the nitrogenous fractions to extensive degradation resulting in an increase in the rate and extent of release of nitrogen (N) in the rumen. Conversely a large proportion of the fermentable organic matter content of grass silage is cell wall material which undergoes a much slower rate of degradation in the rumen. This results in an asynchrony between N and energy release. Formulation of diets that are synchronous for their hourly N and energy release in the rumen has been shown to increase the efficiency of microbial protein synthesis (Sinclair et al., 1995) and increase the growth rate of lambs (Witt et al., 1997). The objectives of the current experiment were to investigate the effects of altering the synchrony of N and energy release in the rumen in diets based on grass silage on intake and performance of lactating ewes.

The contribution of rumen microorganisms to the protein absorbed in the intestine is a key factor to evaluate diets for ruminants, and the urinary excretion of purine derivatives (PD) has recently been proposed to estimate rumen microbial protein synthesis in cows (Verbic et al., 1990). This study refers to the relationship between PD excretion and the microbial nitrogen estimated according to recent protein systems for ruminants.

The purine derivatives (PD) have been proposed as a non-invasive method to estimate microbial-N supply to the small intestine (Chen et al., 1990a; Verbic et al., 1990). The use of PD urinary excretion has the advantage that it can be used with intact animals thus reducing the concern of animal welfare issues. Although, there are known differences in purine metabolism between cattle (B. taurus), sheep and buffaloes (Bubalis bubalis) (Chen et al., 1990b; Chen et al., 1996), no direct comparison of PD urinary excretion has been made so far between cattle especies, therefore, the objective of the present experiment was to compare PD urinary excretion of B. taurus and B. indicus cattle fed similar diets under tropical conditions.

The efficiency of use of feed protein for milk protein production is very poor, particularly for animals offered conserved forages. Contributing to this is the inefficient capture of rumen degradable N in situations where a readily fermentable energy supply is not available for use by the rumen microbial population. The incorporation of a whole crop cereal into a conserved forage could increase rumen protein efficiency. This experiment was carried out to investigate the milk production of dairy cows offered a conserved forage of a whole crop barley and kale bicrop compared with grass silage, and a mixture of the two.

Short-term feeding behaviour (STFB) has been used to elucidate the physiological mechanisms which control eating. It has been proposed as a means by which to predict voluntary food intake, and could be used to quantify behavioural characteristics of the cow. The first step in assessing the usefulness of STFB for these purposes is to identify the major factors which influence STFB. The aim of the study reported here was to evaluate, in dairy cows, the differences in STFB resulting from two different foods, the effect of stage of lactation on STFB, and the effect on STFB of changing from one food to another.

The development by ruminants of strong conditioned flavour aversions (CFAs) to foods associated with the administration of LiCl (an artificial toxin) has demonstrated their potential to avoid feeds that cause negative postingestive consequences (Provenza, 1995). Weaker CFAs are formed when they ingest foods with the detrimental secondary plant compound, oxalic acid (Kyriazakis et al. 1997). Moreover, animals may exhibit conditioned preferences (CFPs) for foods supplying appropriate amounts of nutrients such as nitrogen (Provenza, 1995). In this study we tested whether a continuum exists in the formation of CFAs and CFPs to foods that are associated with increasing availability of sulphur (S) in crossbred ewes.

In recent years there has been an increasing interest in the question of how ruminants develop conditioned flavour preferences or aversions (CFP's, CFA's) towards food flavours associated with the administration of various substances. Several studies have shown that ruminants are able to develop CFA's when pairing a novel food flavour with the administration of secondary compounds which lead to adverse post-ingestive consequences (e.g. activation of the emetic system, hypocalcaemia, Kyriazakis et al., 1997). In addition, CFP's, can be developed through associations between the food properties and the administration of nutrients which lead to positive post-ingestive consequences (e.g. increased nitrogen supply, Villalba and Provenza, 1997). The purpose of this study was to investigate whether a continuum exists between CFP's and CFA's which are developed towards a food flavour associated with the administration of the same nutritive stimulus, given at increasing doses. In addition, the rate of establishment and degree of extinction of such food CFP's and CFA's was also investigated.

Recent studies have shown that when offered a choice of feeds with different concentrations of a particular nutrient (crude protein), sheep can select a diet that meets their current requirements (Kyriazakis and Oldham 1993). To further examine this diet selection behaviour a choice of foods differing in the concentration of S was offered to sheep that were either in a sulphur (S) adequate or a S depleted state. Study of S selection was considered to be the next logical step after protein because of its role in the synthesis of proteins by the rumen micro-organisms.

It is known that if rats learn that a cue reliably precedes eating, its presentation can cause them to initiate a feeding bout when they are apparently sated (Weingarten, 1983, 1985). However, it is currently unclear precisely how such conditioned cues affect appetite. For example, does this type of conditioning elicit food specific appetites or do individuals merely experience a general increase in feeding motivation (Mela & Rogers, 1998)? To address this issue, the present experiment investigated the hypothesis that exposure to a cue (conditioned stimulus: CS) previously paired with a specific food biases diet selection in favour of that food when an individual is given a choice. The objective of the experiment was to enhance our understanding of the behavioural control of feeding, and hence our ability to predict diet selection and food intake.

The experimental subjects were 12 male Lister-hooded rats (initial body-weight 233; SD=20g). Throughout the experiment the subjects were maintained on a 1lh:13h light:dark cycle with lights on at 0700h, and had ad libitum access to a standard laboratory diet during the light phase.

Dietary fructooligosaccharides (FOS) shifted the proportion of propionate (↑) and acetate (↓) compared to transgalactooligosaccharides (TOS) in weaner pigs' ileal digesta, both in vivo and in vitro (Houdijk et al., 1997). This could be related to different fermentation rates between these so-called non-digestible oligosaccharides (NDOs). These rates were studied via the cumulative gas production technique comparing FOS, TOS, and glucose.

The ideal protein profile was developed by Agricultural Research council (1981) and was originally based on the lean tissue component of the pig. Maintenance requirement was then introduced by Fuller et al(1989) but ideal protein profile was still considered to have a constant ratio between all essential amino acids through the life cycle of the pig. However, the maintenance proportion for certain amino acids, such as the sulphur amino acids (SAA), may change as the pig grows. Hence, methionine and cysteine requirements are dependent on the relative balance of maintenance to protein accretion which is based on the protein deposition rate. Therefore, the objective of this study was to determine the relationship between true ileal digestible methionine and cysteine levels in feed and the ideal protein profile during the growing phase of superior genotype pigs.

Whilst wheat is a major component in many pig diets it has the most variable composition of any of the cereals (Bolton & Blair, 1974) with wheat variety and the environment in which it was grown influencing its chemical and physical properties and thus nutritive value. A rapid and inexpensive method for prediction of nutritive value is thus needed to account for these variations in wheat composition. Viscosity is closely related to the soluble arabinoxylan content of wheat (Dusel et al., 1997) with a high in vitro wheat viscosity associated with a reduction in apparent metabolisable energy (AME) for poultry (Classen et al, 1995). The relationship between viscosity and nutritive value for pigs is therefore of interest. The present study investigated the effect of wheat quality measured by extract viscosity, on ileal and overall digestibility using the post-valve ‘T’ caecal (PVTC) canulation method in growing pigs.

Manipulation of dietary nitrogen content can reduce nitrogen excretion (NE) by the pig by 40 per cent (Kay and Lee, 1995), which has major implications for pollution legislation. Past work (Kay and Lee, 1996) has shown that whilst reduced crude protein (CP) diets reduce NE whilst maintaining nitrogen retention (NR), there is also an increase in backfat depth at slaughter. This suggests an ‘energy sparing’ effect from the lower levels of excess amino acids which might be exploited to lower the cost of the reduced CP diets. The objective of this experiment was to determine the NR and NE of growing and finishing pigs offered diets with reduced CP and Digestible Energy (DE) contents compared with commercial diets or diets with reduced CP content only.

Previous work (Blanchard et al, 1995) has suggested that the feeding of a high energy/low protein diet to finishing pigs produces pork of a superior eating quality compared to animals fed conventional energy and protein diets. It has been demonstrated in recent studies (Blanchard et al, 1995) that pork eating quality, particularly tenderness, can be influenced by a change of diet imposed at two weeks prior to slaughter. It has also been suggested (Warkup and Kempster, 1991) that both growth rate and fatness are positively correlated to pork eating quality and that proteolytic enzymes are involved in determining eating quality (Blanchard 1994). The objective of this study was therefore to test these various hypothesis.

Two diets were evaluated: CEP diet (DE 14.0 MJ/kg, Protein 200 g/kg, Lysine 10.0 g/kg) and HELP diet (DE 15.0 MJ/kg, Protein 160 g/kg, Lysine 7.0 g/kg). Treatment 1 animals (n=26) received CEP fed ad libitum 45 kg to 90 kg Iwt. Treatment 2 animals (n=23) received HELP fed ad libitum 45 kg to 90 kg lwt. Treatment 3 animals (n=23) received CEP diet until 14 days prior to slaughter following which they received HELP diet fed ad libitum. A range of carcass and meat quality characteristics were recorded. Grilled loin steaks from each animal were evaluated for eating quality characteristics by trained sensory panel and rated on a scale of 1-8 (increasing with intensity). Activity levels of calpain and calpastatin were measured in samples of LD muscle remove from each carcass 45 minutes after slaughter.

Ruminant products have been criticised for the possible adverse effects of their saturated fatty acids on human health. Conversely, the omega-3 polyunsaturated fatty acids, notably those in fish oils, have been identified as beneficial components of the human diet. Earlier studies have shown that a small, but useful, amount of forage α-linolenic acid (C18:3), an omega-3 fatty acid, appears in ruminant products (Wood and Enser, 1996). The objective of the current work was to evaluate the range of α-linolenic acid concentrations in laboratory grass silages in order to assess the opportunities to modify ensiling techniques to increase the natural delivery of omega-3 fatty acid from grass silage to milk or meat.

Increasing the n-3 polyunsaturated fatty acid (PUFA) content of ruminant products may be important in reducing the incidence of cardiovascular diseases in man. However, there is some evidence to suggest that dietary PUFA are extensively biohydrogenated in the rumen (Choi et al., 1997) whilst other results indicate that long chain PUFA present in fish oil are resistant to biohydrogenation (Ashes et al, 1992). The objective of the present study was to quantify the extent to which n-3 PUFA from different sources are biohydrogenated in the rumen and determine their effects on rumen microbial efficiency.

Milk quota restricts the volume and butterfat content of milk production within the European Community. Consequently, reducing the butterfat concentration of milk enables greater volumes of milk to be produced within a given quota, provided the national butterfat base has been exceeded, as has occurred in the United Kingdom in recent years. For example, milk volume supplied within a given quota may be increased by 0.18 for each 10 g/kg decrease in butterfat content. Consequently, there is considerable interest in developing strategies to decrease butterfat content whilst maintaining milk output. The present study was undertaken to examine the effects of level of fish oil inclusion on the silage intake of, and animal performance from, lactating dairy cows offered two levels of concentrates.

Widespread concerns regarding the detrimental effects of fat consumption on human health (Department of Health, 1994), have led to a decline in the demand for sheep meat. Concerns are mainly centred around the high saturated fatty acid (FA) content and consequent low polyunsaturated:saturated fatty acid ratio (Enser et al., 1996). This ratio may partly be influenced by diet composition, genetic variation or an interaction of these factors. The objectives of the present study were to investigate the effect of different sources of dietary polyunsaturated fatty acids (PUFA) on performance and muscle fatty acid composition and to determine whether breeds differ in their ability to incorporate n-3 PUFA into muscle lipids.

The re-grouping of sows at weaning or after service is a common procedure in pig production systems and is one which can have adverse consequences for both welfare and production. One possibility for overcoming the problem is to return sows to previous groups in which a stable social structure was allowed to develop (Arey and Jamieson, 1996). This would utilise the reportedly well developed abilities of the pig to remember other individuals (Ewbank and Meese, 1971). The aim of this experiment was to determine the effect of time between removal and regrouping on social recognition in sows.

In competitive feeding systems in which sows are group rather than individually fed, aggression can arise as sows compete for limited supplies of food (Csermely and Wood-Gush, 1990). Aggression may also occur as a result of sows’ motivation to feed remaining unsatisfied due to restricted access to food (Buré, 1991). Feeding sows a high fibre diet which will rapidly increase gastric distention (Brouns et al., 1997) may reduce both the motivation to compete for food and aggression associated with sustained feeding motivation. Sows provided with straw bedding may use straw as a foraging substrate with which to express their foraging behaviour. The aim of this experiment was to investigate the interactive effects of a high fibre diet and straw bedding on levels of aggression in floor fed sows.