Two experiments involving the sequential slaughter of intensively fattened store lambs were each carried out over a period of 12 weeks. In the first experiment the lambs were offered a concentrate diet ad libitum. In the second experiment they were offered swede turnips ad libitum with a limited amount of concentrates.

In each experiment, similar groups of lambs were slaughtered at equal intervals in order to measure progressive changes in live weight, carcass weight and dry-matter intake. Carcass-weight gain as a proportion of live-weight gain was found to be 74% in the first experiment and 86% in the second experiment.

Skatole and indole, compounds formed in the large intestine by microbial breakdown of tryptophan, are associated with carcass taint (Hansson et al., 1980). The present work involved the development of a method for detecting the absolute values of the analytes in fat and faeces. The effect on faecal excretion of skatole was also examined following infusion of skatole directly into the caecum. Finally as substrate effects the type and extent of fermentation in the large intestine, different diets were fed and the corresponding faecal and fat skatole levels were determined.

Skatole analysis involved homogenising adipose tissue with methanol and removal of fat by cooling and filtering. Solid phase extraction columns concentrated the analytes to produce samples which gave good resolution by gas liquid chromatography (Porter, Hawe and Walker, 1989). Due to higher levels of skatole in faeces, no concentrating phase was required before detection.

In recent years the quantity of grass silage as big bales has increased substantially, both in the UK and elsewhere. Eyers (1989) reported that about 16% of the grass silage dry matter (DM) conserved in England and Wales was in the form of big bales.

Whilst there is now considerable information on the composition, nutritive value and laboratory procedures for predicting the digestibility and energy value of clamp silage, there are few comparable data for big bale silages. The objectives of the present work were to examine the composition, digestibility and energy value of a population of big bale silages and to compare relationships between laboratory measurements and digestibility in vivo with those derived earlier for clamp silages (Givens et al., 1989).

Confinement of sows in farrowing crates and early weaning of piglets are two major areas of concern in relation to animal welfare in intensive pig production systems. In this project, two alternative lactation systems in which these potential stressors are absent or reduced were evaluated.

36 sows and litters were used in an experiment to evaluate, from weekly performance records and observations of behaviour, two alternative strategies for housing and management during lactation in comparison with a conventional current system:

• (1) Family system (F): Sows were housed throughout in groups of four with voluntary access farrowing pens. Piglets remained with the sows for 12 weeks and a boar was introduced after 3 weeks to induce oestrus.

• (2) Multisuckling system (M): Sows farrowed in individual crates but were grouped in fours in straw pens after 2 weeks. Piglets remained with the sows for 12 weeks and a boar was introduced after 3 weeks.

• (3) Conventional commercial system (C). Sows remained in part-slatted, unbedded farrowing crates throughout a four week lactation. Piglets weaned into flat decks and transfered after four weeks into fully slatted grower pens.

Heterosis for growth rate in pigs is usually expressed, and reviews of European and North American studies have been given by Sellier (1976) and Johnson (1981). Kennedy and Moxley (1980) observed heterosis of 0·044 to 0·067 for weight at 154 days and attributed some of the crossbred advantage to heterosis for resistance to atrophic rhinitis. Similarly, McGuirk, Bourke and Manwaring (1978) attributed some of the heterosis for growth rate in sheep to heterosis for resistance to pneumonia. Although little attention has been paid to interactions between heterosis and health environment, Barlow (1981) concluded from an extensive review of studies involving farm and laboratory animals that heterosis is environment dependent and is enhanced by increased stress. Sellier (1976) commented that it would be useful to examine the degree of heterosis with ‘specific pathogen free’ pigs raised in a healthy environment, and this study examined heterosis for days to 90 kg in Yorkshire × Landrace pigs under three different environments with respect to health conditions.

Heritability estimates of death from enteritis or pneumonia, the two major causes of pre-weaning death at the U.S. Rabbit Experiment Station, Fontana, California, have been estimated. The data consisted of 15,329 observations made at the station from 1946 to 1961.

From birth to 14 days of age the death rate over the years increased from 0·2 to 6·1% During the period from 15 days to 56 days of age (weaning) the enteritis death rate was quite constant over the years (7·5%) while that of enteritis or pneumonia increased from 8·3% to 13·2%.

Heritability of death from enteritis or pneumonia for the period 15 to 56 days of age was estimated on the basis of paternal half sib analysis to be 0·12 ± 0·02. Based on an analysis of differences between dams within sires the corresponding estimate was 0·58 ± 0·05. The difference between the two estimates was attributed to maternal and non-additive genetic effects.

The genetic correlation between the two diseases under discussion was estimated to be 0·66 and 0middot;57 on the basis of differences among sires and among dams within sires respectively.

Breeding plans are suggested on the basis of the parameters estimated.

An experiment was conducted to evaluate the effect of dietary cimaterol, a β-adrenergic agonist, on growth, carcass characteristics and pelt quality of kit mink. The 40 standard dark and 40 sapphire mink kits were assigned to a control or to one of three treatment groups (five males and five females of each colour phase per group). Treatment consisted of the inclusion of 0·5, 2 and 5 mg cimaterol per kg (dry) of a standard ranch mink diet (control). All animals were weighed at the initiation of the experiment (24 July) and at 28-day intervals until 16 October. At slaughter (12 December) body weights were recorded and pelts measured for length and evaluated for fur colour and quality by experienced fur graders. Samples of fur from similar sites on each animal were removed for measurement of guard hair and underfur diameter. Frozen carcasses were analysed for protein and fat content. Mink final weight decreased with increasing concentrations of dietary cimaterol (P < 0·05). Pelt length, which was found to be highly correlated with body size, was also reduced by cimaterol treatment. Feeding 2 and 5 mg cimaterol per kg diet to male kits, and 5 mg/kg to female kits caused a significant reduction in the proportion of carcass fat and increased the proportion of carcass protein (P < 0·05). Fur fibre diameter for both guard hair and underfur was not significantly affected by dietary cimaterol. There was also no significant effect of cimaterol treatment on fur quality. Cimaterol treatment did not result in diversion of nutrients from body proteins to the synthesis of fur and pelt proteins. Results of this research indicate that oral administration of cimaterol to mink will be of little practical value in fur production.

Whilst it is predicted that for finishing cattle (over 350 kg at start) fed grass silage diets, rumen degradable protein (RDP) should provide all protein requirements, previous studies have shown very variable growth responses from protein supplementation of cereal or starchy concentrates fed with grass silage. The protein source usually used being white fish meal which is high in rumen undegradable protein (UDP). This experiment investigated the response to fish meal supplementation of an energy concentrate based on either barley (starchy) or sugar beet feed (SBF, fibrous) when fed with good quality (64‘D’) grass silage to cattle in the finishing period of a traditional 18 month semi-intensive system.

Forty two 15 month and twelve 14 month old Friesian steers were blocked by weight and allocated at random to treatments (weights as fed):

• 1. 2kg barley plus minerals (2B)

• 2. 1.8 kg barley plus 0.2 kg fish meal (2BF)

• 3. 2 kg sugar beet feed plus minerals (2S)

• 4. 1.8 kg sugar beet feed plus 0.2 kg fish meal(2SF)

• 5. 4 kg sugar beet feed plus minerals (4S)

• 6. 4 kg barley plus minerals (4B)

Three experiments are described in which castrated male (steer) calves previously reared to 6 to 7 months of age on dried grass ad libitum gained weight faster, following turnout to pasture, than calves previously reared on a cereal/protein concentrate ad libitum. Rate of gain at pasture was found to be more an effect of previous rate of gain than of diet per se. There were indications that calves whose growth rate had been previously restricted ate more herbage per unit live weight than calves whose growthrate had not been restricted.

The coypu (Myocastor coypus) is an aquatic rodent usually bred for fur production. Fluctuations in fur prices have led to coypu meat being considered as a genuine resource in commercial farms, which contribute to the diversification of agro-ecosystems. To characterize coypus as a meat resource, maternal and heterotic effects on birth weight, weaning weight, slaughter weight, number of days required to attain a weaning weight of l kg, and on two parameters of the Gompertz growth curve (asymptotic weight and maturing rate) were studied. Eight males and eight females of Standard (S) and Cognac (C) genotypes and of their reciprocal crosses (C × S) and (S × C), where the first letter denotes the paternal genotype, were used. Significant genotype, sex and (genotype × sex) interaction effects were evident for most traits. S animals were lighter than С at all ages. Hybrids with С mothers were heavier than their reciprocals. Maternal effects on the parameters of the growth curve were observed only in females. Heterotic effects were extremely significant. Favourable heterotic effects in immature animals were explained by a change in the F1 growth pattern. Males showed a dominant deviation toward low asymptotic weights and overdominance for high maturing rate. Females showed partial dominance of high asymptotic weight and over dominance for high maturing rate. This association of genetic effects would justify a productive system based on a terminal cross using С females and S males because of the higher maturing rate of both hybrids and the maternal effect of С genotype, a combination that allows higher weights at the usual slaughter age (6 months) or butchering of animals at earlier ages.

The problem of applying a linear constraint on expected selection responses in a two-character independent culling levels scheme is investigated. A general equation is derived, the solutions of which specify the culling levels satisfying the constraint applied. Examples are given to demonstrate how different constraints can be applied by transforming one or more of the characters under selection.

Previous studies have shown that the interaction between limiting vitamin A (VA) and an alcohol dehydrogenase 1 C (ADH1C) variant in beef cattle results in increased intramuscular fat in the longissimus thoracis muscle in one genotype when fed low dietary VA. Although quality grade is important for increased profitability and improving taste characteristics of beef products, limiting VA too drastically can impair animal welfare. The objectives of this study were to determine if this marker-assisted management strategy would be effective, and whether any impairment in immune function would occur in a feedlot setting. Mixed breed beef steers (n=2000) were sorted into 40 feedlot pens so that all combinations of ADH1C genotype (TT or CT), VA level (50% or 100% of recommended) and hormonal implant status (implanted (IMP) or non-implanted (NI)) were equally represented within the population. The VA×ADH1C interaction was not observed. An implant status × ADH1C interaction was observed with average daily gain (ADG; P=0.03). Steers that were IMP and CT had higher ADG than IMP TT (CT=1.69 and TT=1.62 kg/day), whereas both genotypes in the NI steers were lower (CT=1.29 and TT=1.32 kg/day). Implant status was shown to affect dry matter intake (DMI; IMP=8.55 and NI=7.87 kg; P<0.01), total days-on-feed (IMP=164.4 and NI 210.5 days; P<0.01), USDA yield grade (YIELD; IMP=2.40 and NI=2.77; P<0.01), marbling score (MARB; IMP=392 and NI=455; P<0.01), longissimus thoracis area (LTA; IMP=85.0 and NI=80.7 cm2; P=0.01) and backfat thickness (FAT; IMP=8.0 and NI 10.0 mm; P<0.01). Overall, IMP animals finished on fewer total days-on-feed with higher ADG, DMI, larger LTA, and lower YIELD, MARB and FAT. To investigate immune function parameters, crossbred steers (n=18) were selected from a prior feeding trial so that all combinations of ADH1C (TT, CT and CC) and VA (25% or 75%) were equally represented. Blood cell count analysis and peripheral blood mononuclear cell proliferation and stimulation assays were conducted. None of these immune parameters were affected by VA level. Treatment and mortality records were examined in the 2000 steer population, where no correlations with ADH1C, implant status or VA level were observed. Due to no VA × ADH1C interaction, this nutrigenetic marker-assisted management strategy is not effective at this time in commercial beef cattle feedlots, however, supplementing VA at a level as low as 25% of recommended in finishing rations would likely not result in signs of immune dysfunction.

A map of the bovine genome will be an important tool for identifying genes causing congenital defects, and those controlling disease susceptibility and production traits in both beef and dairy cattle. Over 300 genes have already been mapped and a low resolution map should be available within two years. We are actively involved in the EC funded European Bovine Genome Mapping Group. To date our work has involved the development of markers and studies of experimental designs, two necessary precursors of a large scale bovine genome mapping project. In this article we briefly describe ongoing projects underpinning and improving the prospects for mapping bovine genes affecting disease and production.

For a linkage map of the bovine genome to be of use, the markers should display high levels of polymorphism. The most common markers on the map of the human genome are restriction fragment length polymorphisms (RFLPs), however these are usually diallelic, often with one allele at high frequency. We have been concentrating our efforts on the production of a relatively new class of marker, the micro-satellite.

It is now known that growing pigs can utilise considerable quantities of non-starch polysaccharides (NSP) in their diets (Bulman et al., 1989). These materials are fermented in the hind-gut of the animal to produce volatile fatty acids (VFAs) which are then used as an energy source, unlike starch from conventional cereal-based rations which is digested by the host enzymes of the animals. Little is known about how animals adjust to a sudden change in dietary energy source and the present experiments were designed to investigate the metabolic adaptations in pigs fed either a conventional cereal-based diet or one containing 300 g sugar beet pulp/kg diet.

Recent trials with cows fed grass silage have shown significant increases in intake and in yields of milk and milk solids when the crude protein (CP) concentration in a supplementary concentrate was raised. Giving additional CP in the concentrate was a more effective strategy for improving yields of milk and milk protein than giving extra energy (Aston et al 1992). The objective of this trial was to examine the influence of changes to the amount and pattern of distribution of CP supplied in a fixed concentrate ration given with grass silage ad libitum.

Fifty-five Holstein-Friesian cows in their second and subsequent lactations were given a standard diet for two weeks from calving and then were used in a continuous feeding trial from weeks 4 to 21. The cows received 5 kg of fresh concentrate daily containing 156 (LP), 245 (MP) or 338 (HP) g CP per kg dry matter (DM), MP comprised equal amounts of LP and HP. Concentrate carbohydrate sources were cereals and digestible fibre and CP was increased by a mixture of 3:1 soya:fish meals. Grass silage contained 253 g toluene DM/kg, 162 g CP/kg DM, D value in vivo 0.723, pH 3.7, fermentation acids 135 g/kg DM of which 0.85 was lactic acid and NH3-N 91 g/kg total N.

The chemical composition and the energy and protein value of five batches of condensed distillers solubles (CDS) originating from wheat were determined. The net energy for lactation (NEL) was derived from digestion coefficients obtained with sheep. The true protein digested in the small intestine (DVE) and the rumen degradable protein balance (OEB) were based on the rumen degradation rate (kdD), the rumen undegradable fraction (U) and intestinal digestibility of undegraded protein (%DVBE) predicted by regression equations derived from a data set of 28 protein feeds with kdD, U and %DVBE determined in situ. The CDS is a by-product with a high, but very variable CP content (238 to 495 g/kg DM). The CP contained on average 81% amino acids, with glutamine as main component (on average 21.8% of CP) and a relatively good lysine proportion (3.0%). Further, CDS contains quite a lot of crude fat (mean±SD: 71±14 g/kg DM), glycerol (95±52 g/kg DM) and sugars (123±24 g/kg DM) resulting in a high organic matter digestibility (88.6±3.0%) and high NEL content (8.3±0.4 MJ/kg DM). The protein value showed a large variation, with DVE ranging from 122 to 244 g/kg DM and OEB from 50 to 204 g/kg DM. Wheat CDS is a rich source of minerals and trace elements with exception of calcium.

The objective of the experiment reported here was to provide the UK farmer with sufficient information to allow economic utilisation of space in flat-deck accommodation without a reduction in performance of the weaned pig.

Two experiments at separate sites were used to compare different methods of achieving the same stocking density. At site 1 pen size was altered by means of a moveable partition while at site 2 it was the number of pigs per pen which was altered.

Freedom of movement and freedom to express normal behaviour are fundamental principles underlying most welfare guidelines (e.g. Brambell, 1965). The restrictive nature of the farrowing crate and its potential to limit the repertoire of species specific behaviours may influence the welfare of the sow (Higginson, 1985). The objective of this study was to examine sow behaviour in different farrowing systems and specifically to investigate the behavioural component of improved winter production results in a less restrictive farrowing pen system (Rudd et al., Paper 18, 1993 BSAP Winter Meeting).

Three farrowing systems in neighbouring rooms were compared. Two systems allowed the sows to move freely, i) five strawed pens (2.5m x 1.5m) with farrowing rail (Pen), and ii) five crates modified to allow the sows to walk through (Free Crate). Sows had access via a passageway to a transponder-controlled feeder and a North facing (shaded) outside area with two water drinkers. Piglets were contained in their home Pen or Free Crate area by a small barrier (30cm high).

Genetic parameters were estimated for wool quality, fleece characteristics and lamb production traits for Scottish Blackface sheep reared under extensive hill conditions in the UK. In two separate studies, heritabilities and genetic correlations were estimated for wool quality traits measured on lambs at 5 months of age and again on the shorn fleece a year later. The wool traits included birth coat length (BCT), 10-point scores for proportion of grey and kemp fibres present in the fleece (grey, kemp), British Wool Marketing Board (BWMB) recommendation (REC), greasy fleece weight (FLWT), BWMB fleece grade (FLGR), and average staple length (ASL). Genetic and phenotypic correlations were estimated between lamb wool traits and lamb live weights at birth (BWT), marking (at mid lactation with an average age of 7 weeks) (MWT), weaning (at an average age of 17 weeks) (WWT) and slaughter (SLWT), average fat depth (AVFD) and average muscle depth (MD). Individual lamb carcass measurements included Meat and Livestock Commission (MLC) conformation score (CONF) and fat class (FATC). Heritability estimates measured on 2524 or more live lambs were 0·69, 0·52, 0·26, 0·42 and 0·31 for BCT, ASL, grey, kemp and REC respectively. Heritability estimates for traits measured on the shorn fleece a year later for 1415 ewes were 0·37, 0·02, 0·57, 0·43, 0·46 and 0·14 for ASL, grey, kemp, REC, FLWT and FLGR respectively. Genetic correlations between FLWT in hoggets and other wool were positive and moderate to high in magnitude, ranging from 0·22 for kemp in lambs to 0·48 for grey in hoggets. Genetic correlations between REC and live-weight traits were 0·39 for MWT, 0·37 for WWT and 0·44 for SLWT. Genetic correlation between ASL and ultrasonic fat depth was 0·15 and for ASL and ultrasonic muscle depth was -0·30. The results indicate that the simple scoring systems derived to assess these traits are useful indicators of fleece quality, are highly repeatable over time and are a good gauge of likely future wool production. The results indicate that selection for heavier, leaner lambs should not compromise fleece quality, as assessed in this study.