The number of entire male pigs slaughtered in Great Britain has increased steadily over the past 10 years and they now constitute some 45 per cent of the national population. Although there has been concern about possible boar taint, the industry has apparently experienced few problems. However, boar taint continues to be a major concern in other countries, possibly reflecting heavier slaughter weights and breed differences. Limited evidence indicates that earlier maturing breeds, such as the Pietrain and Duroc, tend to have more taint than other breeds of the same weight or age. This has implications for the wider use of specialist meat type sires which now supply atleast 10 per cent of the genes in the commercial British slaughter population.

Microbial metabolism of dietary tryptophan in the gastro-intestinal tract results in the production of skatole and indole. These compounds, collectively classed as indoles, may be absorbed and deposited in carcass tissue and have been associated with taints especially in entire male pigs (Hansson et al., 1980). As indoles are readily absorbed over the entire tract in humans (Fordtran et al., 1964), it was suggested by Lundstrom et al. (1988) that diet may influence skatole production and hence levels in the carcass. The objectives of this study were to determine the sites of skatole production in the gastrointestinal tract and the effect of diet on production and carcass levels.

There is increasing concern within all sectors of the UK pig industry with meat quality and particularly the eating quality of pork. Against this background, a collaborative study involving 6 organisations was carried out to investigate the relative influences of a number of production factors on the eating quality of fresh pigmeat. The results relating to two of these factors, namely feeding regime and sex of pig, are reported here.

The purpose of this paper is (a) to emphasise the importance of raw milk quality at the point of production (b) to consider the relative benefits of seeking to improve quality at the point of production compared with the point of manufacture and (c) to consider possible future quality demands which might be imposed on raw milk.

The intake of silage has been shown to either increase (England & Gill, 1985), decrease (Gill et al., 1987) or remain unchanged (Steen, 1985) in response to increasing levels of fishmeal supplementation. The aim of this experiment was to investigate the effect of two levels of fishmeal supplementation on voluntary intake, together with studies on digestion in the rumen, to try to elucidate the different mechanisms involved.

The loss of digestible energy from ruminant feeds as methane gas is often assumed to be about 0.08 of gross energy (GE) intake. This represents a significant loss of feed energy and recently concern has been expressed about the importance of methane as a gas which contributes to global warming. As methane is a gaseous loss, its measurement requires specialised equipment. Therefore the metabolisable energy (ME) content of many feedstuffs is estimated using a predicted methane energy loss.

Many feedstuffs consist of a variety of proteins which, differing in size and structure, may undergo proteolysis in the rumen at different rates. The conventional use of single, constant coefficients to describe the proportion of protein degraded in the rumen (e.g. 0.65 for soyabean meal) may, therefore, be inappropriate. Soyabeans contain two major storage proteins, β-conglycinin and glycinin. Two experiments were conducted to assess differences in rate of proteolysis between α and β sub-units of β-conglycinin (molecular weight approximately 66kD and 56kD, respectively) and acidic and basic sub-units of glycinin (approximately 36kD and 23kD, respectively).

Lactic acid is the predominant organic acid found in well preserved silages, accounting for up to 150 g/kg dry matter. However, lactic acid has been shown to have a depressive effect on the voluntary intake of hay and silage by cattle (Thomas et al, 1980; Montgomery et al, 1963). The objective of the present study was to investigate how the response of cattle to short term intra-ruminal infusions of lactic acid might be mediated, using fistulated steers adapted to diets of chopped hay or silage by measuring the patterns of feed consumption during the day, together with changes In the concentration of metabolites within the rumen.

Tetronasin is an ionophore which improves feed conversion efficiency in ruminants (Bartle et al, 1988). Its nutritional effects are at least partly derived from its influence on nitrogen and energy metabolism in the rumen. The mode of action of tetronasin is therefore similar to monensin and although it is more potent than monensin, it has a similar spectrum of antimicrobial activity (Newbold et al, 1988). The aim of the present study was to compare the effects of the inclusion of tetronasin or monensin in the diet on the rumen fermentation.

Three mature sheep weighing approximately 50 kg and fitted with rumen cannulae were fed 1 kg/d of a mixed diet of hay, barley, molasses, fishmeal and vitamins/minerals (500, 299.5, 100, 91 and 9.5 g/kg dry matter respectively) in two equal meals. A control diet (no addition, C), tetronasin (10 ppm in the diet, T) or monensin (33 ppm, M) were compared in a 3 x 3 Latin square. Periods were 28 days long with samples taken on two consecutive days during the last 5 days. Samples of rumen fluid were withdrawn at 0, 1, 2, 4 and 6 h after the morning feed for the determination of pH, volatile fatty acids (VFA) L-lactic acid and ammonia concentrations.

Variation in litter size in sheep is essentially attributable to variation in ovulation rate and embryo survival. Genetic variation in litter size, both among and within breeds, is largely attributable to variation in ovulation rate. While there is evidence for genetic differences among breeds in embryo survival the contribution of this component to within breed variation appears to be minor (Hanrahan, 1982). The impact of selection based on litter size on its component traits should reflect the relative contribution of these components to within breed variation. Data from two lines of Galway sheep, a Control line and one selected for increased prolificacy (Hanrahan and Timon, 1978), have been used to provide evidence on this point.

Details relating to the selection experiment which provided the data for the present study are in Hanrahan (1984). Briefly a flock of Galway sheep was assembled from industry sources (both pedigree and non-pedigree) between 1963 and 1965.

Lamb performance at grass falls in July/August on upland farms. Allowing sward height to rise has been recognised as having an ameliorating effect [Keeling, 1987). The objective of this trial was to determine the influence of both sward quantity (sward height) and sward quality [sward type) on ewe and lamb performance from mid April to September. A further objective was the evaluation of clover as an alternative to nitrogen fertiliser.

Three contrasting perennial ryegrass based swards were established in May 1987 for use in 1988 and 1989: a late heading diploid variety (D). CONTENDER and a late heading tetraploid variety [T) CONDESA sown alone or with S184 small leaved white clover [TO]. [D] swards represent the control being the normal upland pasture type. [T] companion ryegrass varieties have higher palatability and intake characteristics and, producing fewer tillers, are a compatible companion grass to white clover. Small leaved white clover was used owing to its higher persistency and dry matter production under continuous sheep grazing.

Both glucosinolates and S-methyl cysteine sulphoxide (SMCO) have been implicated in the suboptimal intakes observed among lambs consuming forage brassicas. However, the effects on animal performance of the compounds administered in isolation have been marginal (Barry et al, 1982) and the toxicity of the compounds may be enhanced by interactions between their physiological effects. In order to test this, an experiment was conducted in which rumen metabolites of both SMCO and the predominant kale glucosinolate, sinigrin, were administered in combination to sheep and effects on voluntary intake and blood chemistry were examined. SMCO is hydrolysed in the rumen to dimethyl disulphide by a bacterial enzyme while sinigrin undergoes hydrolysis in crushed plant tissue to allyl isothiocyanate and allyl cyanide under plant enzyme catalysis.

In growing lambs a high proportion of protein retained (0.2-0.3) may be stored in wool. Protein retention is known to be increased by treating sheep with B agonists and there are indications that the extra protein is stored mainly in the carcass (Williams, 1987; Fiems, 1987). Wool growth rate at any time is determined by the relative availability of nutrients to all body tissues and is affected by, for example, pregnancy. It is also dependent on the kinetics of all competing biochemical reactions, which are altered by hormones (Black and Reis, 1979).

To investigate the partition of protein between wool and other body tissues, a nitrogen balance trial was carried out with lambs fed on a diet with or without the B agonist, Cimaterol (Boehringer Ingelheim, Ingelheim, West Germany).

High perinatal mortality in sheep flocks worldwide remains a major economic and welfare issue. Maternal behaviour and lamb vigour are both considered major variables affecting lamb survival, but there is little data to describe their relative importance. The aim of this study was to investigate the relationships between lamb vigour and maternal behaviour at parturition. With the increase in hill ewes being crossed to longwool breeds there is an interest in the relative survivability of these lambs. This study compared the behaviour of Mule [Bluefaced Leicester x Blackface] lambs with purebred Scottish Blackface lambs.

Data on 32 third parity single and twin-bearing Blackface ewes lambing indoors were collected by focal animal observations on the ewe's grooming behaviour. These observations included details of the time spent grooming specific areas of the lamb's body and also general activity and udder-seeking behaviour of the lambs. Observations lasted 10 minutes and were made at parturition and then at 30 and 90 minute intervals. The data was transformed by arcsin. for proportions, or log, for frequencies, and analysed by Analysis of Variance,

Harnessing the resources of commercial pig farms to augment research and development facilities provided by Universities, central Government funding and by commerce is not a new approach. The commercial farm sector, with appropriate deployment, provides a very useful resource. While these facilities can be most valuable in contributing to the overall R and D effort one must be aware of their actual and potential limitations.

Because field trials often necessitate less detailed measurments than are possible in a true research environment, they are often believed to represent a poorer form of science. However, this is a very short-sighted view because there are particular benefits to be derived from carefully designed and conducted field trials which cannot be satisfied by smaller, more detailed studies.Within the context of reproduction research the objective is to understand the basic physiological mechanisms controlling reproduction, and to identify the nature and extent of reproductive wastage and its causes. The logical extension of this is to develop appropriate treatment strategies to overcome these limitations, some of which may be satisfied by changes in animal management while others will require recourse to pharmaceutical manipulation.

Pollution of the environment by livestock wastes occurs in many instances due to the difficulties involved in managing, storing and spreading manure and effluents. The total amount of neat manure produced by housed livestock for England and Wales has been calculated to be 70 million tonnes a year. All this has to be collected, stored and applied to agricultural land. There are, in addition 60 million tonnes of manure which livestock drop as they graze grass and forage crops. Problems of controlling the adequacy of farm waste systems are compounded by the scattered nature of livestock farms, the numbers (approximately 120,000 in England and Wales), and that often, the farm buildings are in close proximity to water courses.

Environmental pollution caused by livestock farming affects water, air and the soil.

This is caused by the escape of liquids or the dumping of solid wastes into water courses. The polluting effect is caused by water soluble organic matter, suspended solids and minerals. The result of the entry of polluting matter into water is the rapid growth of micro-organisms which deplete the oxygen content of the receiving water.

A few decades ago in The Netherlands in the same way as in a number of other West-European countries a development started of excessive growth of animal husbandry. While in former agricultural production where animals were involved more or less a balance existed between the number of animals to be held on a certain farm, and the area available for feed and fodder production, this balance was now disturbed by the import of huge quantities of feed and raw materials for feed production. This has led to the situation that a mineral excess from animal manure exists for The Netherlands as a whole. In specific parts of the country, especially the sandy area, mineral availability has grown to excessive amounts. The environmental problems involved are related to:

• -leaching of nitrate to groundwater at a concentration level which causes unsuitability for drinking water purposes;

• -accumulation of phosphorus in the soil profile, and in case of P-saturation of the soil, leaching to groundwater and surface water, thus inducing eutrophlcation problems;

• -leaching of K to groundwater at a concentration level exceeding the potassium standard;

• -accumulation of heavy metals in soil, especially Cd, Cu and Zn, at a level which may induce malfunctioning of soil, both with respect to water quality, and to crop yield and crop composition.

Much of the N ingested by livestock is excreted; slurries from housed animals therefore represent substantial pools of N. Recycling through the soil-piant-animal system can reduce fertilizer usage, but current waste management practices often result in water or atmospheric pollution. This may occur directly, for example through contamination of water by a leaking slurry store, or indirectly through losses of plant nutrients, especially N, to the wider environment. The adverse effects of gaseous losses, from NH3, volatilisation and denitrification, and of nitrate leaching are becoming increasingly well recognised. Such losses also reduce the amounts of N available for uptake by plants and may account for low, variable crop responses to applied slurries. The objectives of this study are to quantify losses of N following application of slurries to land and to examine strategies for reduction, so conserving N for uptake by plants.

Following application of slurries to land, mainly grassland, N losses through NH3, volatilisation were measured by using small wind tunnels or micrometeorological techniques, through denitrification by a soil core incubation method with acetylene inhibition and through nitrate leaching in lysimeter experiments.

Previous studies at this Institute have shown that there is an interaction between level of supplementary feeding and protein content in the supplement. For example, a given milk yield can be obtained by offering supplements of high crude protein content at much lower levels than would be required with conventional supplements. Furthermore, this approach enables a greater reliance on the forage component of the diet, particularly where high quality grass silage is available. The objective of the present large scale study was to determine milk production responses to supplements of differing protein content, given with high quality grass silage, and to examine effects on ration digestibility.

The experiment was carried out over a two year period, with a total of 168 autumn-calving British Friesian dairy cows. Supplements containing either 100, 220, 340 or 460 g crude protein (CP)/kg fresh weight were offered from day 14 of lactation. Each supplement was offered at four levels, with 9 animals per treatment.