In the previous paper, Sutton et al. (1985) examined the effect of concentrate type on the performance of lactating dairy cows and reported significant effects with respect to silage intake and milk protein concentration. In this experiment, conducted in parallel with that reported by Sutton et al. (1988), the effect of concentrate type on nutrient digestion in the rumen and protein supply to the tissues of lactating cows was examined, although the comparison was restricted to examination of the high protein diets only.

New schemes describing the protein nutrition of ruminants consider both host and microbe requirements for nitrogenous compounds, truly absorbed amino N (TAAN) and rumen degradable N (RDN) respectively. This has made the prediction of the energetic efficiency of rumen microbial protein yield (E,MiN) crucial. However there is little guidance concerning the prediction of E,MiN since there are few consistent relationships in the literature. We face the dilemma that current techniques for measuring E,MiN are costly, invasive and laborious which makes it difficult to conduct large, designed and replicated experiments to investigate sources of variation. We have adopted the much simpler techniques of measuring urinary allantoin excretion to investigate sources of variation in E,MiN. Our objective was to investigate effects on E,MiN of varying rumen outflow rates by nutritional (level of intake and diet digestibility), and non-nutrition (supplementary NaHCO3) methods.

Experiments were designed to investigate the effect of sub-clinical cobalt deficiency in pregnant hill sheep, on lamb viability. This form of the deficiency is not characterised by clinical symptoms. The disease is therefore difficult to detect, and may be of economic importance to farms on land of marginal cobalt status.

In each of two trials, both with sixty Scottish Blackface x Swaledale ewes, animals were randomly assigned to three treatment groups: A. Cobalt-deficient intake throughout pregnancy; B. Initially cobalt-sufficient intake, but deficient from mid-pregnancy (Trial 1) or initially cobalt-deficient intake, but repleted from mid-term (Trial 2); C. Cobalt-sufficient intake throughout pregnancy. A cobalt-deficient ration (<0.06 mg Co/kg DM) of Timothy hay, micronised maize and maize gluten, was fed from tupping in Trial 1, and from two months before tupping in Trial 2. Treated animals received a weekly oral dose of 0.7 mg Co/head.

Vitamin B12 (microbiological and radio-immuno assays) and methylmalonic acid (capillary gas chromatography) were analysed in ewe and lamb sera, as indicators of cobalt status. Levels of passively acquired immunity were measured by analysis of lamb sera, sampled at two and four weeks post-partum, for immunoglobulin G (IgG) and by the zinc sulphate turbidity test (ZSTT).

Soluble, phosphate glass boluses containing copper, cobalt and selenium have proved successful in elevating and maintaining blood levels of these trace minerals in sheep (Driver et al, 1985 & 1986). In 1983 these boluses were marketed as the trace mineral supplement COSECURE. Recently trials with glasses of various solubilities were carried out and one formulation (Code EX) proved superior to all glasses tested to date (Driver et al, 1988). Last year the performance of this more soluble glass was compared with that of the commercial product, COSECURE, on a site which in previous years had shown severe copper deficiency.

On day 0 (22 October), 20 Scottish-Blackface ewes each received one new (EX) bolus, another 20 received COSECURE boluses and a further 15 were left as untreated controls. Blood samples were taken at intervals over the following 330 days and assayed for plasma copper and serum caeruloplasmin for copper status and erythrocyte glutathione peroxidase (GSHPx) as a measure of selenium status. Boluses were recovered from culled ewes at 341 days after bolusing. The results were analysed by an analysis of variance.

Previous experiments with early weaned lambs at pasture have indicated the large protein losses which occur in the rumen (prairie grass 3%, ryegrass 22%, white clover 29% and lucerne 42%) (Cruickshank et al. 1985). Growth appeared to be related to duodenal protein supply and these were similar for the grasses and for the legumes (grasses 228 g/d liveweight gain and 0.92 g duodenal NAN/kg W/d, legumes 314 g/d and 1.22 g duodenal NAN/kg W/d). Efficiency of use of absorbed amino acid also appeared to be low (0.43). These results suggested that growth of lambs grazing these high quality pastures could be increased by increasing duodenal protein supply and/or by amino acid supplementation. Because of the large protein losses which occur in the rumen of animals grazing legume pastures in particular there is scope for manipulation of this aspect either through supplementation or plant breeding.

The objective of this experiment was to examine the liveweight gain response of lambs grazing grass or legume pastures to fishmeal supplementation and also the response of lambs grazing legume pastures to two forms of protected amino acid supplements designed to supplement first limiting amino acid(s).

Real-time ultrasonic scanning of pregnant ewes has become popular, and offers many potential advantages in flocks lambing at 110-170%. This experiment was set up to quantify the beneficial effect on sheep performance that can be obtained, from correct late pregnancy feeding of outwintered, twin-bearing hill ewes.

A hill flock numbering 369 Scottish Blackface ewes in regular ages were pregnancy scanned in mid-February 1985 and 1986 (45-92 days post-conception). From the identified twin-bearing ewes, 102 ewes in 1985 and 166 ewes in 1986 were randomised into two groups in early March, six weeks before lambing was due to commence.

Efficient lean growth may, in future, be the main selection objective in terminal sire breeds of sheep. The genetic relationships between growth rate, food intake and food conversion ratio need to be quantified, so that calculation of selection indices for growth rate and carcass lean content can take account of correlated changes in food intake.

Both level of feeding and dietary composition have been demonstrated to influence bacterial colonisation and diarrhoea in the weaned pig (Smith & Hall 1968, Bertschinger et al 1978, Lecce et al 1983). Kenworthy and Allen 1966 proposed that “the stimulus to bacterial growth derives from the hosts response mechanisms to intestinal irritation” and that the enterotoxigenic E Coli “Acts as an exacerbating agent rather than a primary pathogen” (Kenworthy et al 1967).

Several workers have suggested that the primary intestinal response is villus atrophy, an elevation in crypt cell mitosis (by up to x10) and crypt cell hyperplasia, associated with malabsorption, mal-digestion and increased intra-epithelial lymphocytes. Such a response is characteristic of a T cell mediated type IV hypersensitivity (Ferguson 1980). Miller et al (1984) have therefore suggested that one of the factors which may contribute to the aetiology of postweaning diarrhoea is a transient hypersensitivity to dietary antigens prior to the development of oral tolerance.

Neonatal and post-weaning losses represent significant economic loss to the pig industry and in terms of animal welfare the loss of one in ten piglets within the first four weeks of life seems unacceptable. Many losses occur within hours of birth due to a variety of causes, such as overlying, chilling, starvation and disease. More losses occur in the first few days after weaning and the principal cause of these losses is disease. Enteric and systemic infections are therefore responsible for many of the deaths that occur in the early weeks of life. In addition to the pathogenic density in the environment the piglets immune responses determine susceptibility or resistance to disease challenge.

Passive and active immunity are related in a number of ways in their expression but both are profoundly affected by the various stressors that piglets are confronted with in the first few weeks of life. Stress stimulates increased concentrations of plasma Cortisol and this in turn depresses the various components of an immune response.

Amongst the stressors, weaning, mixing into new social groups and relocation may have the biggest effects. In modern systems of pig production piglets are weaned at 3-4 weeks of age and there is constant pressure on the use of expensive buildings, there is often a compaction of these stressors.

Selection for improved growth and efficiency has probably led to later maturity in pigs, so that gilts only reach puberty at heavier weights than they did ten years ago. A consequence of this might be that it would be beneficial to delay first service in the modern gilt. Previous analysis of a breeding company's herd records showed a significant relationship (b=0.05) between age at first effective service and total numbers born in the gilt litter.

As a result of these findings a minimum age at first service has been stipulated for purebred gilts of 240 days across all NPD herds. Farrowings under this regime commenced in February 1987, and the reproductive performance since that date has been monitored and compared against that for the previous 12 months.

To help resolve the dynamics of fatty tissue mobilisation, and interactions with milk yield and reproductive performance, the experiment reported here takes gilts and sows over four parities to one of two levels of strategic fatness at parturition, and then studies the consequences of high or low lactation feed intakes in conjunction with strong or weak milk withdrawal potentials as achieved by manipulation of litter size.

One hundred and two Large White x Landrace F1 hybrid gilts were purchased from the Cotswold Pig Development Company Limited at about 30 kg live weight. At mating, animals were allocated at random to one of B treatments comprising: two levels [fat and thin) of target backfat thickness at parturition (10-14 mm. T vs 20-24 mm. F): two daily feeding levels (high and low) during 4-week lactation [3 kg, L vs ad libitum to a maximum of 7 kg. H): and two sizes of sucking litter (5 vs 9 in parity I. and 6 vs 10 in parities 2. 3 and 4).

The influence of fatness at parturition, nutrition during lactation and the size of litter upon changes in backfat depth, live weight and conformation of sows over four parities has been presented in the first report. The present report will deal with the consequences for reproductive performance and production efficiency.

One hundred and two Large White x Landrace Fl hybrid gilts were purchased from the Cotswold Pig Development Company Limited at about 30 kg live weight. At mating, animals were allocated at random to one of B treatments comprising: two levels (fat and thin) of target backfat thickness at parturition (10-14 mm. T vs 20-24 mm. F): two daily feeding levels (high and low) during 4-week lactation (3 kg. L vs ad libitum to a maximum of 7 kg. H): and two sizes of sucking litter (5 vs 9 in parity 1, and 6 vs 10 in parities 2, 3 and 4).

Recent work in the United States (Reese, Moser, Peo, Lewis, Zimmerman, Kinder and Stroup 1982) and in Australia (King and Williams, 1984) has clearly shown that nutrition during lactation can affect the fertility of young sows. If first-litter sows are restricted in food intake during lactation, so that they lose body weight and backfat, they take longer to return to oestrus after weaning than their counterparts fed ad libitum. To reproduce successfully the sow must have some mechanism(s) of monitoring its nutritional status, preferably before conception takes place. It is difficult to imagine mechanisms capable of monitoring body reserves per se. It is more likely that the sow can monitor changes in its body reserves, for example, by measuring the rate of lipid mobilized from adipose tissue or the rate of protein breakdown from muscles, or both.

Crossbred gilts (Landrace x Large White) were selected at about 45 kg body weight (approx 3 months of age) and allocated to treatment according to litter and live weight. A total of 22 groups each of 24 animals was selected. Within each group gilts were fed (13.0 MJ DE/kg, 160 g/kg CP) either ad libitum (High), 2.0 kg/day (Medium) or 1.8 kg/day (Low) from selection through until mating.

Body reserves are important in reproduction because they can be used by the sow to buffer the nutritional stress through a low intake of food in lactation (Mullan and Williams, 1988). Quantitative information on the body composition of first-litter sows during lactation is clearly required to establish what body reserves are mobilized during lactation, and how this relates to subsequent reproductive performance. The aim of this study was to quantify the body reserves of first-litter sows at farrowing and to measure the change in these reserves during lactation.

Animals selected for body composition studies were from the High-High, High-Low, Low-High and Low-Low groups of an experiment described by Mullan and Williams (1988). Animals were selected according to bodyweight, depth of backfat and litter size, with the object to have animals that were representative of those in the earlier experiment. Sows were removed from their litter, weighed and the depth of backfat measured by ultrasound at the P2. Within three hours of weaning animals were slaughtered and the head, trotters, tail, viscera one side of the carcass were frozen, minced and chemically analysed for lipid, protein, water and ash.

All species of ruminants which have evolved in cold or temperate climates are seasonal breeders. This includes many species which have been domesticated such as sheep, goats, cattle, deer and camels. In the wild, births usually occur in spring or summer at a time of year optimal to survival of the offspring; this means that the period of fertility is restricted to a short mating or rutting season. The environmental factors which ultimately dictate the birth season (eg temperature and food supply) are different from the factors which act as proximate cues to dictate the time of the mating season (eg day-length).

In all seasonal breeders, the seasonal cycle In fertility is driven by changes in the pulsatile secretion of LHRH from the brain which dictates the level of release of LH and FSH from the anterior pituitary gland and the consequent activity of the ovaries or testes. Steroid hormones from the gonads act on the numerous target tissues including the brain where they modulate the LHRH pulse-generator and influence sexual and aggressive behaviour.

The supply of lamb meat to the market varies more than other red meats. This is hardly surprising given the seasonal breeding characteristic of the great majority of sheep in this country. The Variable Premium system that currently operates in this country is designed to try and even-out the supply of ‘finished’ lamb. There is a natural spread of lambing and a wide variety of techniques used to ‘finish’ store lambs. In spite of all these factors there is still a marked shortage of lambs available particularly in the months of April and May.

The application of ultrasonics to the evaluation of live cattle has been carried out in bull performance testing for several years. The machine used for this was the Scanogram. The fact that this machine is no longer being produced and the emergence of several new machines has prompted this trial to evaluate seven ultrasonic machines.

A total of 49 bulls, 27 Limousin x Friesian and 22 Charolais x Friesian, were evaluated and slaughtered in four batches of approximately equal size, over four weeks. Each batch was of one breed.

Age, live weight at evaluation and subjective assessments of fatness and conformation were recorded together with fat and muscle measurements by the Delphi (Delphi Instruments Ltd, New Zealand), Meritronics (Merit, Lowson and French, England), Scanogram (Ithaco Incorporated, USA), Vetscan (Company no longer in existence), Kaijo Denki (Medata Systems Ltd, England), Velocity of Sound (Prototype developed at IFR-Bristol, England) and Warren (Prototype developed by J Warren) ultrasonic machines.

Downgrading of lamb carcasses for overfatness is a major source of revenue loss to U.K. sheep farmers due to loss of EEC payments worth up to £20 per head. The difficulties of assessing fatness on live lambs by subjective assessment using lumbar palpation and the fact that in live markets the same techniques are used by the MLC graders cause problems to the farmer attempting to avoid overfat lambs. The trial reported here addresses the problem of how to feed lambs identified at live certification as overfat with the objective of reducing fatness but retaining the meat content of the carcass. Work by Hovell, Orskov, MacLeod and McDonald (1983) using intragastric infusion techniques showed how lambs could maintain positive N balance on diets that were below accepted maintenance levels for energy but had adequate protein.

In the first trial 76 Suffolk X overfat lambs previously fed on roots and concentrates outside were allocated to initial slaughter (28) or barley straw ad lib (24) versus barley straw ad lib + 100 g/day fishmeal pellets (24). Lambs were slaughtered after 14, 28 or 42 days on trial. Data was collected on the straw intake and liveweight change, but slaughter data was not available.

It is well recognised that heifers, which are the source of approximately 0.35 of all clean cattle slaughtered for beef in Britain, yield carcasses that are different from those of steers in several commercially important aspects: they are lighter, are scored fatter than steers and have poorer conformation. Live and carcass wholesale prices for heifers are, on average, lower than for steers.

In the USA, studies have shown that yield grade equations, deveoped to predict the ‘cutability’ of carcasses, overestimate this in heifers compared with steers, ie. heifers yield less of the defined primal cuts than steers at the same levels of fat thickness over the rib, rib eye area, kidney + pelvic + heart fat proportion, and carcass weight (predictor variables). However, it has recently been shown that this bias is apparently the result of differences between the sexes in the relation between the fat depth measurement and the total amount of fat trim. In Britain, estimates of yield are based on visual scores of fatness and conformation, but there Is little information on the relations between carcass morphology and composition in the two sexes, differences in which may have important commercial implications.

Consumer demand for lean meat production has meant that prediction of lean meat content of the carcass has become an important part of commercial pig production at many levels. At the production level, precise prediction of lean in the live pig is required to rank accurately selection candidates to ensure rapid genetic progress and to aid management decisions. At the marketing level, classification schemes pay high premiums for leanness. Payment under current classification schemes is based on relatively simple back fat measurements. However, in neither case is there ‘built in’ differentiation for breed or genotype but in the future, grading schemes are likely to place greater emphasis on leanness. The purpose of this study was thus to determine whether lean prediction in the carcass was independent of slaughter weight and genetic type, to identify the best predictors of leanness and to estimate multiple correlation coefficients for predicting lean in the carcass from lean in individual joints. Pigs from four commercial genotypes were performance tested, serially slaughtered between 80kg and 120kg, after which fat depths were recorded and full sides dissected. Various predictors of lean were then compared.