Two trials were completed using a total of 135 female hoggets from 5 to 7 months of age. The effect of implanting 15 or 30 mg. testosterone propionate or 2·5 mg. oestradiol benzoate plus 25 mg. testosterone propionate was assessed on average daily gain, slaughter characteristics and carcass yield. In the second trial some additional data were obtained on carcass quality.

No significant effect of testosterone with or without oestradiol could be demonstrated on average daily gain, carcass yield, carcass score or the proportion of retail cuts in the carcass. There was some indication that the treatment could yield carcasses with less subcutaneous fat without diminution of eye muscle size.

In the first of two experiments of 6 × 6 Latin-square design a diet of barley, soya bean meal and fish meal, known to give an adequate lysine intake (56 g/day) at the level of feeding adopted, was diluted with maize starch to give crude protein intakes ranging between 448 and 923 g/day but with the lysine intake held constant by using synthetic lysine in the diets. The diets were given to sows suckling ten piglets between days 12 and 30 of lactation. Dietary amino acid adequacy was assessed by changes in plasma urea, urinary urea, urinary nitrogen and plasma amino acid concentrations. The dietary amino acid supply became limiting with a protein intake of approximately 730 g/day. In the second experiment, a diet of similar composition was used with varying additions of synthetic threonine, methionine, isoleucine and tryptophan: the control diet contained all the synthetic amino acids added, the basal diet none and the other diets were formed by adding groups of three out of the four synthetic amino acids. On the basis of some of the variables studied, it was concluded that, for this diet, threonine was the limiting amino acid after lysine.

Obestatin is a gastrointestinal peptide having wide-ranging effects on cell proliferation; however, its mechanism of action remains poorly understood. Thus, the aim of the study was to elucidate the effect of exogenous obestatin on the postnatal structural development of the small intestine. Seven-day-old piglets with an average BW of 1.56 ± 0.23 kg were divided into four groups (n = 10) that received intragastrically obestatin (2, 10 or 15 μg/kg BW) or vehicle. After a 6-day experimental period, morphological analysis of gastrointestinal tract and small intestine wall (mitosis and apoptosis indexes, histomorphometry of mucosa and muscularis layers) was performed. The study revealed a seemingly incoherent pattern of the histological structure of the small intestine among the experimental groups, suggesting that the effect of obestatin is both intestinal segment specific and dose dependent. Histomorphometric analysis of the small intestine showed that higher doses of obestatin seem to promote the structural development of the duodenum while simultaneously hindering the maturation of more distal parts of the intestine. Intragastric administration of obestatin increased the crypt mitotic index in all segments of the small intestine with the strongest pro-mitotic activity following the administration of obestatin at a dose of 10 and 15 μg/kg BW. The significant differences in the number of apoptotic cells in the intestinal villi among the groups were observed only in proximal jejunum and ileum. In conclusion, it seems that obestatin shows a broad-spectrum of activity in the gastrointestinal tract of newborn piglets, being able to accelerate its structural development. However, the varied effect depending on the intestinal segment or the concentration of exogenous obestatin causes that further research is needed to clarify the exact mechanism of this phenomenon.

Current ration formulation schemes for calculating the feeding requirements of dairy cattle are primarily based upon empirical relationships between nutrient availability and milk production. Although these schemes can provide reasonable estimates of nutrient requirements, they are inadequate at predicting the responses in milk yield and composition to changes in nutrient availability. Clearly, a more integrated approach is required where the predictions are based on the metabolic fate of the absorbed nutrients. An ability to achieve this requires knowledge of the precursors used for milk protein synthesis and how nutrient intake influences their partition to the mammary gland for utilisation in milk protein biosynthesis.

I must first apologize for the speed with which this paper has had to be written. I returned from the United States seven days ago and in that time have had to collect my thoughts, scattered to no small degree by a passage which I am sure the censor will have no objection to me describing as rough in the extreme.

Some of the views that I shall express are influenced, naturally, by what I have seen in America. In that country there are initiative, scope and financial resources for breeding experiments with farm animals which, outside of Russia, are not rivalled anywhere in the world. Constant attention to the progress of these long-term breeding experiments will be necessary and the need of the stimulating and thought-provoking effect of similar work in this country, preferably in conjunction with the Dominions, is obvious.

Animals show considerable individual variation in many behaviour patterns such as feeding and mating behaviour. Often, this individual variability is ignored in favour of a more general description of the population. However, this may mask important information regarding the causes and functions of this individual variability. Behavioural work on other species has suggested that individuals tend to respond actively or passively to environmental challenge. It is of interest to know if a similar dimension of responsiveness exists in pigs as it may serve, amongst other things, to explain the considerable individual variability in pigs responses to putitive stresses such as tethered housing. This paper describes a series of tests made of behavioural responsiveness in pigs to assess the extent of consistent variability in individuals responses to a wide variety of environmental challenges.

The subjects were two groups [Group A and B: n = 26 and 36 respectively) of modern hybrid non-pregnant gilts [Cotswold Pig Development Company Ltd, UK). Initially, the gilts were subjected to a number of tests of behavioural responsiveness at the Cotswold unit.

Mating and the resultant conception is a critical event in the operation of a pig production unit. The boar's presence is known to influence the reproductive performance of the female pig in several ways, such as the onset of puberty, the weaning-to-conception interval, behavioural oestrus, conception and the number of piglets born in the subsequent litter. To optimise the productive benefits from this interactive process and for ease of husbandry there are several key requirements.

The boar must be housed to maintain his health, welfare and reproductive ability, the newly weaned sow must be aware of the boar's presence and an area must be provided where mating can be successfully executed. Additionally, there are second-order objectives of considerable importance: the easy and clean provision of feed and water, a minimal effort muck removal system, pens which provide easy access for stock and pigmen whilst allowing easy stock transfers. The multiplicity of objectives must be integrated and satisfied in a successful design.

1. The experiment involved four pairs of Jersey cows in a double reversal trial with two treatments.

2. The control and acetate treatments involved iso-caloric concentrate mixtures together with hay. The concentrates and hay were given in constant ratio of 3 : 1 and total feed intake was regulated according to milk yield. Cows on the acetate treatment received a dilute solution of fatty acids (1·7 % w/w) and an all-cereal concentrate mixture; those on the control diet received water and a concentrate containing 10% groundnut meal. The dilute solution of fatty acids provided approximately 31 % of the total digestible crude protein intake as ammonia-N, and 208 g acetate and 34 g propionate per day.

3. The two treatments gave similar dry-matter intakes. The acetate treatment caused a slight and significant depression of milk yield but the fat content of the milk and fat-corrected milk yield were slightly increased by treatment, though not significantly so. The results have been discussed with reference to the end products of digestion in the rumen and role of ammonia-N as a substitute for protein-N.

The paper outlines the major problems in scientifically assessing the nature and quality of the man-animal interface and the difficulties in isolating its effects on animal production. Research epistemologies in this area are thwart with difficulties as it is virtually impossible to isolate individual factors. For example, while it is possible to devise ‘pleasant’ and ‘unpleasant’ handling treatments; as defined by level and nature of the physical interaction of the human body with that of the animal; it is not possible to separate physical handling from aspects such as voice tones, gestures, smell, sound of foot movements, or other ‘vibes’ transmitted in the experiment. Thus, any changes in ‘production’ may arise from a number of inter-woven components. It is also of relevance that the quality of the man-animal interface is a perceived construct and that the animal may perceive both applied ‘pleasant’ and ‘unpleasant’ stimuli as undesirable. Limitations of research paradigms are raised, for example, in experimental situations the environment may well be ‘richer', and with more humans present, than in commercial situations. The nature of the interface may thus be somewhat different.

I am very honoured to be invited to give this Lecture. I knew John Hammond well, and am personally in his debt for the many kindnesses and considerations he extended to me early on in my career. He was, in more ways than one, a giant of a man, and it is most fitting that this Society should honour his memory by inviting special lectures in his honour, and especially on the 50th anniversary of the founding of the British Society of Animal Production (BSAP) in 1944.

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.

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.

It is difficult for the visitor to New Zealand to realise that practically all of the five million acres of pasture land now devoted to dairying was, a matter of seventy years ago, dense rain-forest, scrubland or undrained swamp. Practically the whole of the Manawatu and Taranaki and large portions of the Waikato and North Auckland, which are the principal dairying districts today, were in forest when the introduction of refrigerated ocean transport in 1882 made possible the development of New Zealand’s dairy industry.

The first step in bringing in forest was the felling of giant trees such as rimu, matai and totara and the undergrowth of smaller trees and vines. Sometimes the bigger timber trees were milled, but too often they were merely felled and the fire-stick was applied to leave an indescribable mess of partially burned trunks and stumps.

Seventy-six pigs provided with indwelling venous catheters were exposed for 40 min to a temperature of 40°C and 100% relative humidity. Plasma 17-OHCS levels were determined during the period of stress and up to 24 hr thereafter. The results obtained were assessed in relation to backfat thickness, and eye-muscle area and appearance (Göfö value) in groups of 10 animals showing maximum and minimum values for these parameters. In all the animals the heat and humidity stress brought about an increase in the plasma levels of 17-OHCS. Significant differences were more often found in the induced 17-OHCS levels in those animals which appeared to be leaner on the basis of backfat thickness and eye-muscle area and produced poorer quality meat than in those with less lean of better quality. These results support the notion that there is increased activity of the adrenals of leaner types of pig which produce meat of poor quality.

Genes from the Chinese Meishan pig have the potential to enhance reproductive performance of European pigs (Bidanel, 1989; Haley and Lee, 1990). In order to allow prediction of the impact of Meishan genes In a range of alternative improvement programmes all traits of economic importance must be evaluated and genetic crossbreeding effects estimated. This paper reports the results of a crossbreeding study of meat and carcass quality traits recorded at the last rib position.

Animals were purebred Meishan (MS) and Large White (LW) pigs, and reciprocal F1 crosses: Meishan ♂ x Large White ♀ (MS x LW) and Large White ♂ x Meishan ♀ (LW x MS). The animals were born In first and second parity litters at the Institute of Animal Physiology and Genetics Research, Edinburgh and performance tested at the University of Newcastle upon Tyne. The trial was performed in two replicates of equal size, each corresponding to a single parity, with a total of 273 animals. In both replicates, females and entire males of all four genotypes were tested (approximately equal numbers of each genotype and sex). Animals were housed indoors in like sex and genotype groups of six (three pairs of full sibs). Tests started at pen mean of approximately 35 kg of weight and ended at pen mean of approximately 70 kg. Animals were fed ad libitum on a commercial ration (195 g/kg crude protein, 13.2 MJ digestible energy/kg).

Nutritional stressors may cause negative effects on animal health and growth and lead to significant economic impact. Adipose tissue is an endocrine organ producing, mediators and hormones, called adipokines. They play a dynamic role in body homeostasis and in the regulation of energy expenditure, interacting with feeding behavior, hormones and growth factors. This in vitro study aimed to investigate how nutritional conditions and growth hormone (GH) can influence nitric oxide (NO) production and the expression and secretion of three important adipokines, that is leptin, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), by swine adipocytes. In our experimental model, mesenchymal stem cells from omental adipose tissue were induced to adipogenic differentiation. After differentiation, adipocytes were incubated for 24 h (T0) with DMEM/Ham’s F12 (group A) or DMEM/Ham’s F12 salts (group B), a DMEM/Ham’s F12 formulation deprived of nutritional components. Primary adipocyte cells were also co-cultured for 4 h (T+4) or 12 h (T+12) with or without anterior pituitary slices. To stimulate GH secretion by pituitary cells, growth hormone releasing hormone at 10−8 M was added at the start of the incubation times (4 or 12 h). At T0, T+4 and T+12, NO production, leptin, IL-6 and TNF-α expression and secretion were measured. NO increased (P<0.05) up to twofold in restricted culture conditions. Deprived medium and coincubation with anterior pituitary positively influenced leptin secretion and expression. TNF-α was expressed and secreted only in deprived culture condition groups (B, B1 and B2). Nutrients availability and pituitary co-culture did not affect IL-6 expression and secretion. Our study shows an endocrine function for porcine adipocytes. In our model, adipocytes readily responded to nutritional inputs by secretion of molecules affecting energy balance. This secretion capacity was modulated by GH. Improving our knowledge of the role of adipocyte in the endocrine system, may lead to a more complete understanding of regulating energy balance in swine.

A method of selection for two or more traits is investigated, where the selected individuals have to be the highest performing for any one trait, but not necessarily for several traits. The efficiency of selection of extremes is contrasted with the methods of culling levels and tandem selection. It is shown to be superior to culling level selection when the proportion of individuals retained for breeding exceeds 0·5. At higher selection intensities, the effectiveness of selection of extremes falls between that of culling levels and tandem selection.

The effects of 18 buffalo sires, used in 2 years of a progeny-testing programme, on the subsequent lactation performances of their mates, were investigated from a study of 685 lactation records. The traits studied were: milk production, lactation length, length of post partum anoestrus, number of services per conception and length of service period (calving to conception). Parity of calving and sire had a significant effect on 305-day milk yield and lactation length of the mates. Between the 2 years, the sires did not differ for any of the traits of their mates. Although the breeding value of the sires, high or low, did not differ significantly, the sires with high breeding value tended to depress the milk production in the subsequent lactation of their mates and vice versa (r= −0·05). The birth weight of the calves significantly affected milk production. It was concluded that all methods of sire evaluation are likely to be biased by the effect of sires.

In order to evaluate heat stress and circadian rhythm 46 nulliparous rabbit does with a BW of 3.67 ± 0.05 kg (s.e.) were used. They were clipped once or not and rectal temperature, feed and water intake were recorded for 24 h. From this group, 43 rabbit does were mated 7 days after rectal measurements, and randomly assigned to one out of two breeding systems (including in both systems rabbit does that had been clipped or not). In the control one (C) rabbit does were mated 14 days after parturition and litter weaned at 35 days of age, and in the extensive one (E) they were mated 21 after parturition and weaned at 42 days of age. Rabbit doe and litter performance were recorded for 6 months (first three cycles). Two hundred twenty-eight weaned rabbits were divided into two cage sizes: 0.5 and 0.25 m2 with eight and four rabbits per cage, respectively, to study growing performance. Farm and rectal temperatures were minimal and feed and water intake maximal during the night (P < 0.001). Unclipped rabbit does showed higher rectal temperature (P = 0.045) and lower feed intake (P = 0.019) respect to clipped does, which are symptoms of heat stress. Neither breeding system nor cycle number influenced fertility, total number of kits born, born alive or dead per litter (91.6%, 6.98, 5.80 and 1.19 on average, respectively). Kit mortality during lactation tended to increase in E compared with C group (48.5% v. 63.4%; P = 0.070), reducing the number of kits at weaning per litter by 33% (P = 0.038). It also increased in the second and third cycles compared with the first (P ⩽ 0.054). It resulted that feed efficiency (g weaned kits/g feed intake does + litter) tended to decrease in E respect C group (P = 0.093), whereas it was impaired successively from the first to the third cycle by 48% (P = 0.014). Growing rabbits from the E group were heavier at weaning (by 38%; P < 0.001), showed a higher feed intake (+7.4%) and lower feed efficiency (−8.4%) throughout the fattening period (P ⩽ 0.056) respect to C group. However, age at slaughter was not different respect to C group (77.3 days on average). Cage size had minor influence in growing performance. In conclusion, rabbit doe and litter productivity impaired when lactation is extended from 35 to 42 days and along successive reproductive cycles.

Monensin, an ionophore, and AO, a fungal feed additive, are growth promoters which modify rumen fermentation. Previous studies have shown that monensin increased propionate, the efficiency of bacterial growth and the flow of protein from the rumen and decreased methane production and fibre digestion (Schelling, 1984), whereas AO increased bacterial numbers and fibre digestion and lowered methane production (Frumholtz et al., 1989; Fondevila et al., 1990). The aim of the present study was to determine, using Rusitec, the effects on rumen fermentation of combining these additives.