Previously, we have reported on work in dairy goats using stable isotope kinetics to examine the precursors for milk protein synthesis (1). Contrary to a previous hypothesis (2), these results suggested that blood free amino acids (AA) are not simply transported into the mammary gland and incorporated directly into milk protein. Although the latter may still occur, a substantial amount of the AA for milk protein synthesis appears to be channelled through constitutive mammary gland protein(s) first. Moreover, the data indicated that a proportion (12-20%) of the casein protein precursor may be derived from extra-mammary sources other than blood free AA, e.g. peptides and/or proteins. It may be possible therefore to alter milk protein synthesis by the provision of different forms of precursor amino acids. Since the previous study was in goats during early lactation (day 61 ± 11), the present study reports on the precursors for milk protein synthesis in goats during late lactation, and allows a comparison between stages of lactation.

Most considerations of protein digestion assume that amino acids are made available to the body tissues as the free form but recent reports suggest that a substantial portion may be absorbed from the stomach region of ruminants as small peptides (1). However, the quantitative relevance of this absorption to amino acid supply to tissues remains unclear. We have previously indicated that in early lactation at least part of the amino acid supply to the lactating mammary gland may be met from blood derived peptides or small proteins (2) but at present there is no direct evidence to suggest that peptides can contribute amino acids to the gland for milk protein synthesis. However, it has been demonstrated in dairy animals that the uptake of certain amino acids across the mammary gland is insufficient to account for their output in milk protein (J.A. Metcalf, unpublished observation) and the possible utilisation of amino acids in ‘non-free’ form must be considered. The present study involves the use of a dual-labelled tracer approach to evaluate the ability of the mammary gland to utilise amino acids in peptide-bound form for milk protein synthesis. The technique involves infusion into the external pudic artery (EPA) supplying one half of die gland of a dipeptide XY where Y is a [13C]-labelled amino acid, coupled with a simultaneous (jugular) infusion of the amino acid Y but with a deuterium label. The jugular infusion allows a correction for recycled amino acid generated by whole animal (i.e. non-mammary) hydrolysis of the infused peptide. In theory if the half of the gland receiving direct infusion of the dipeptide utilises peptide-bound Y for milk protein synthesis then the ratio of [13C] : deuterium should be greater in casein secreted from that half of the gland compared with the other (control) side of the gland.

Although milk output is known to be affected by dietary manipulation, studies have so far failed to provide sufficient information to successfully predict dietary effects on both milk protein content and yield (Thomas 1983). In a further effort to determine the metabolic control of milk protein synthesis three diets containing different levels of crude protein were fed to four Holstein-Friesian cows in early- to mid-lactation, and metabolite flow across the mammary gland was measured in relation to milk protein production.

The urinary excretion of allantoin and uric acid (collectively purine derivatives, or PD) provides an estimate of the yield of microbial protein (MP) from the rumen. The technique is useful for estimating rumen efficiency of dairy cows, but due to the problems associated with urine collection, its use is limited on the large scale. Measuring PD in milk would allow more routine assessments to be carried out on a practical level.

Twelve multiparous mid-lactation Holstein/Friesian cows were used in a 3x3 Latin square changeover experiment with 3 four-week periods. Cows were allocated to squares on the basis of their mean milk yield of the 7 days prior to the trial. Within squares, treatments were randomly allocated to each cow. The first 25 days of each experimental period were used for adjustment, and the last 3 for the collection of milk and urine samples.

In ruminants, daily urinary excretion of purine derivatives (PD) reflects the absorption of microbial purines and can be used as an index of microbial protein supply (Chen, Ørskov and Hovell, 1991). The application could be extended to farm conditions if measurements based on spot urine samples or plasma could serve as an alternative index. The objective of this study was to examine whether PD concentrations in spot urine or plasma samples vary diurnally during a given feeding regime and if they reflect differences in daily PD excretion induced by varying feed intake.

In modern protein evaluation systems the protein unit (PU) of a feedstuff and the requirement of PU is expressed as true protein assumed to be absorbed from the small intestine. Total PU supply originates from feed protein escaping rumen degradation and from microbial protein synthesised in the rumen. Escape feed PU is calculated from crude protein (CP) multiplied by the escape CP fraction, amino acid content of escape CP and small intestinal digestibility of escape amino acids. Microbial PU is calculated from the energy source for microbial growth multiplied by the efficiency by which this energy is used for microbial CP synthesis, amino acid content of microbial CP and the digestibility in the small intestine of microbial amino acids.

In the past selection programmes for pigs have been based on measurements from individually housed animals. The manual weighing of food and refusals to obtain information on individual food intake is labour-consuming, and the housing method different to that found on most commercial farms where growing pigs are housed in groups. The selection of pigs in one environment to be kept in another often leads to a discrepancy between performance results achieved by pig breeders and those obtained in a commercial situation (Merks, 1989).

The development of genotypes with high protein deposition rates (PDR) has brought into question previously accepted theories concerning growth, protein deposition and nutrient requirements of pigs. It is clear that the full potential for lean deposition of these new genotypes can only be realized if we adopt appropriate nutritional strategies. As a first step the work reported here was conducted to determine the protein deposition rate of highly selected hybrid boars and to evaluate nitrogen balance and carcass composition techniques for estimating PDR.

Recent health recommendations regarding fat intake have highlighted the importance of consuming polyunsaturated fatty acids (British Nutrition Foundation, 1992) in a manner which takes into consideration the physiologically competitive n-6 and n-3 fatty acid families. Through dietary modification, pig meat and meat products provide a valuable contribution toward this aim (Morgan et al, 1992) although concerns relating to changes in physical and taste properties are hindrances to commercial acceptance. The aim of this investigation was therefore to obtain information on the optimum length of time required to significantly alter the fatty acid composition of pig meat without incurring deleterious physical effects.

Microbial activity in the gut of pigs may influence meat eating quality through the fermentation of dietary substrates to intermediate and end products which can be absorbed and concentrated in tissue. In turn, it may thus be possible to modify the eating quality of pig meat by dietary manipulation of gut microbial activity. This can be achieved by using feed ingredients with high levels of fibre (non-starch polysaccharides NSP). The response may differ depending on NSP composition, its effects on microbial activity and the concentration of substrates which are fermented to compounds having either negative or positive effects on meat quality. For example, Lundstrom et al. (1988) were able to formulate a high-fibre diet which increased fat skatole concentrations and associated undesirable flavours in meat from boars. On the other hand Longland et al. (1991) found that the overall acceptability of meat from growing pigs was enhanced by feeding up to 300 g/kg of dried sugar beet pulp (SBP), which is a rich source of readily fermentable NSP.

The aim of this study was to compare effects on meat eating and fat quality from growing pigs fed SBP (unmolassed) and oatfeed (OF), a cereal by-product high in insoluble NSP which is less readily degraded.

Research conducted during the last few years shows that several factors affect the eating quality of pork and that it is possible to obtain good eating quality at low levels of fat in the carcass (ie. P2 ˂ 10mm). A Blueprint approach to meat quality improvement can be taken by combining appropriate genetic, nutritional, animal welfare and meat processing inputs.

It is widely believed that care taken during cooking is important if the full benefit of the improved practices is to be realised. However there is little objective research on which to base recommendations. This study set out to examine the effects of cooking temperature on grilled loin steaks, a popular product although vulnerable to cooking abuse.

Personality or emotionality development in animals is influenced profoundly by experiences and stimuli in the early stages of growth. Previous work at Leeds University (Stedman and Varley, 1990) has shown that there are large variations in the personality characteristics of multiparous sows and these are stable and repeatable over time. The work also showed that personality traits may account for a significant proportion (17.8 %) in the overall variations in prolificacy in the pig.

The effect of different environments on individual animals may have its foundation in the perception of stress by each individual. What may be tolerable for one animal may not be so for another. Stress is a notoriously difficult concept to evaluate in terms of its effects on animals and on the production of animal products. The components of a high stress system will include; very high stocking densities, repeated new social grouping, barren environments, poor thermoregulation and human-animal interactions which cause either physical or psychological trauma to the animals. Reproductive processes are particularly affected by stress and some of the manifestations of this are: reduced litter size, failure to show oestrus, poor conception rates and sporadic puberty attainment.

Recent legislation prohibiting the use of individual confinement systems for dry sows has led to the adoption of group housed systems which have perceived welfare advantages. The feeding system for dry sows and gilts is fundamental to welfare and production; problems such as abnormal behaviours, aggression and psychological stress, caused by poor nutrient distribution in group systems, must be addressed.

In this study the relative merits of three feeding systems for group housed gilts were investigated in relation to welfare and production.

Previous work has shown that feeding regime and not physical restraint is a major cause in the development of stereotypies in closely confined sows, (Teriouw et al, 1991). However, this and a previous report on the relationship between feeding regime and stereotypies in sows (Appleby and Lawrence, 1987) have only studied gilts in their first pregnancy. The objective of this present work was to examine longer-term effects of feeding regime and housing on the development of stereotypies in sows.

Thirty-two sows (Cotswold Pig Development Co. Ltd, UK) were allocated to either loose (Lo) or tether (Te) housing and to Low (L; 2.5 kg/day) or high (H; 4.0 kg/day) food levels in a balanced design. Apart from social contact and freedom of movement the housing systems were similar including the provision of chains to the loose housed animals. The behavioural response to these treatments was observed over parities 2,3 and 4 using a time sampling technique, and the data analysed by analysis of variance and linear correlation.

The scientific assessment of farm animal welfare requires an amalgam of different measures of both physiology and behaviour. Behavioural measures are relatively easy to obtain but non-invasive measures of internal physiology are somewhat harder to achieve. An increase in the use of applied physiology in training regimes of human athletes, has led to an improved technology of heart rate monitors, making the measurement of heart rates painless and easy to record.

The objective of this experiment was to use a human heart rate monitor to investigate differences in heart rate response at feeding between sows housed in three different dry sow housing conditions. Schouten et al (1991) have demonstrated differences in heart rate response at feeding between loose-housed and tethered sows. In the study reported here, stall-housed sows were compared with sows housed in small groups and sows housed in a large group with an Electronic Feeder System (EFS).

The major welfare problems of farrowing accommodation concern piglet crushing, disease and weakness. The farrowing crate has been designed to prevent these piglet welfare problems. However, for the sow the restrictive nature of the farrowing crate may decrease her welfare. As studies of free-ranging pigs show, sows often choose to leave their young at intervals (Jensen et. al., 1991) and this is prevented in the conventional farrowing crate. The development of a less restrictive farrowing system might allow the sow to express behaviour similar to that seen in free-ranging conditions. The objective of this experiment was to compare the production performance of the farrowing crate with farrowing systems which allow the sow to leave her offspring.

Inaccurate prediction of silage intake is often the greatest source of error in ration formulation but improvements have been hindered by an inadequate description of the silage fermentation in advisory practice. Until recently, only pH and ammonia N have been routinely measured as indicators of silage fermentation characteristics. A new method, based on research in Finland (Moisio and Heikonen, 1989) has been developed and is now in use by SAC. This involves automated titration of juice squeezed from the silage to pH 2 (with HC1) followed by stepwise titration (with NaOH) to pH 12. Concentrations of juice constituents are predicted from the buffering capacities measured over segments of the titration curve (pH 2 to pH 12). Calibrations have been obtained empirically by the addition of known increments of standards to a range of silage juices. Proportions of variance (R2) of measurements made by reference methods accounted for by predictions from titrations for a validation set of 93 silages were 0.90, 0.78, 0.92, 0.82 and 0.82 for lactic acid, acetic+butyric acids (VFA), soluble N, sugar and ammonia N respectively.

In general cows have higher intakes and higher milk yields when outdoors grazing pasture compared to indoors consuming grass silage. However, this observation is not valid as a direct comparison of grass and silage due to the following reasons. Firstly, the cows consuming the silage and grass are usually at different stages of lactation and secondly the silage has not been produced from the herbage being grazed. There is little information available in the literature comparing the intakes of grass and silage harvested from the same sward at the same stage of maturity when fed to lactating dairy animals at similar stages of lactation. The present study was initiated as part of a series of studies at this Institute, to evaluate factors affecting silage intake. The main aims of this study were to determine the actual effect which ensiling “per se” had firstly on dry matter intake and secondly on animal performance by the lactating dairy cow.

In many parts of Europe complementary forage crops such as maize silage, fodder beet and whole crop cereals have been widely used in dairy cow ration. In France, Germany and Holland, over 2.5 million hectares of maize are grown for silage, while in Denmark fodder beet and whole crop cereals are an integral part of most dairy cow rations. With the introduction of milk quota many farmers in the UK tried to maintain margin/litre by placing greater reliance on high quality home produced forage. On many grassland farms this strategy met with limited success as grass silage is often an unpredictable and variable commodity which is prone to low intakes. At the same time evidence was being accumulated in the UK as to the potential benefits of mixed forage diets in dairy cow ration. As a result the Milk Marketing Board of England and Wales established a programme work to determine the effect of incorporating a range of alternative forages or forage substitutes into grass silage based diets, on DM intake and milk production.

Cane molasses is extensively used as an energy source for cattle because of its high content of water soluble carbohydrates. However, its very low crude protein content and its ability to reduce non-protein-nitrogen (NPN) utilisation in ruminants in comparison with cereal grains may restrict its inclusion in dairy cow rations. Adding vegetable protein or urea to a cow ration containing high levels of molasses may therefore result in a better match between the nitrogen and energy requirements of rumen microorganisms. A previous experiment showed that lactating dairy cows could be fed molasses in a grass silage-based complete diet up to 312 g/kg DM without adverse effects (Yan and Roberts, 1992). The present experiment was subsequently undertaken to evaluate the responses of lactating dairy cows to protein levels in complete diets containing this high level of molasses