The economic implications of sub-standard performance in animal production which result from the increased incidence of metabolic disorders such as bovine ketosis and ovine pregnancy toxaemia, and accompanying reduced reproductive performance, plus the detrimental effects of undernutrition, are well known. Together they pinpoint the desirability of being able to assess the adequacy of rations in supplying nutrients, particularly energy, to provide an appropriate diet. The assessment of nutritional status is becoming increasingly important as farmers attempt to maintain enterprise profitability by either reducing feed costs and maintaining production, or by maintaining feed costs and increasing overall production, or by a combination of these two procedures.

Domesticated livestock have always been an important part of agricultural production. They have been utilized as scavengers to consume the production which could not otherwise be marketed at a better return. Livestock systems were typically very small holdings and were cared for in the odd time that the farmer would have from tending crops. This has been referred to as chores. The chores were done in the morning before field work and in the evening after return from the field. There was slow change in this system or in the pattern of production until after World War II. Since that time because of the shifts in population and the desire for better living conditions that could be afforded in urban areas livestock production has been systemized. Dairy production was one of the first livestock operations to be mechanized. Perhaps this is due to the milking operation being one of the most odious chores which had to be performed in livestock production. The milking machine was a very welcome addition to the farm industry.

There are three major markets for lamb — retail and catering domestic markets, and the export market. Most of the latter is within the European Community (EC) and as 1992 approaches the differences between the domestic and EC export markets will become less distinct. The basis of specifications for all of these markets, and sectors within them, is weight range, fatness and conformation. The majority of lamb is sold to the consumer (whether retail or catering) in a ‘bone-in’ form and weight range is therefore critical for many cuts, for example chops and leg joints, in determining either weight at sale (and price of pack) or portion size.

In the domestic market major multiple supermarkets are gaining market share at the expense of independent butchers. With their purchasing power they can and do impose increasingly tight and sophisticated specifications. All, for their majority of ‘bone-in’ cuts, specify a carcass weight range of 16 to 20 kg. It is estimated by the Meat and Livestock Commission (MLC) that around 8% of lamb is now sold retail in a boneless form (boneless joints, lamb steaks, cubed lamb and minced lamb) and that this is a growing sector of the lamb market. Lamb is a small carcass unit (in comparison with beef and pork), has a high bone content and thus the cost of boning-out lamb carcasses is high. To reduce costs there is advantage in buying heavier lambs (but only if they are lean) and the premium specification for lambs for producing boneless cuts (and other forms of products) are increasingly in the range 20 to 24 kg.

Fatness continues to be the primary consumer negative about lamb. For ‘bone-in’ cuts it is difficult to trim, for boneless cuts extra trimming is possible but at the cost of reduced yields. There is a common specification for fatness in terms of MLC carcass classification — fat class 2 or 3L with increasing preference for the former. Conformation is the least important aspect of domestic market specifications. Nevertheless, for ‘bone-in’ cuts, particularly the important leg joint, shape is considered by many meat buyers as being important and most will be specifying carcasses of at least average shape, i.e. carcass class R. The export market is more complicated in terms of basic specifications. For the major market in northern and central France the specification is more or less identical to that of the major supermarkets in the domestic market. In south Europe requirement is for a much lighter lamb, 8 to 12 kg, very lean, fat class 1 and 2, and shape is almost irrelevant. Belgium and Germany require heavier lambs (18 to 22 kg) and this reflects usage in catering and processing.

There is growing interest in quality assurance schemes for lamb in the UK based on various carcass, slaughterhouse, storage and distribution factors.

Changes in eating patterns for reasons of cost, health or convenience, have resulted in reduced consumption of lamb. Carcass meat is being replaced by more processed, added value meat in the home, but novel lamb products have been difficult to develop due to small muscle size, hard fat and strong flavours. If value is to be added to lamb, texture and flavour of lamb and lamb products must be optimized. Whilst the use of electrical stimulation for beef carcasses, to avoid potential cold-induced toughening in modern chilling systems, is standard practice, little British lamb is stimulated in this way.

Restructuring can upgrade smaller or tougher and/or fatter parts of the carcass. It allows for regular portions of standard shape, size and composition, as in reformed hams, burgers, grillsteaks or sausages. The small size of the lamb carcass makes it expensive to bone and trim fat and connective tissue for the production of such products. This could be an increasing disadvantage if high quality, reformed, fresh products, using new binding technologies such as alginate or enzyme systems, gain a significant market share.

The ready meals market is expanding rapidly and although meat may not be the major component, it is usually the most expensive. These products may be fully sterile shelf-stable, cooked and frozen, or, more commonly, cooked and chilled with a shelf-life of a few days with carefully controlled refrigeration. Packaging has been highly developed for marketing these products. Unfortunately, traditional lamb products, such as moussaka and shepherds pie, are often now made from cheaper beef.

Larger lamb carcasses with lower fat, the use of mechanical bone removal or robotic butchery systems, innovative product or recipe design and the use of good packaging and presentation, would all aid in the development of lamb meat and meat product sales.

Leg weakness reduces the amount of time broilers spend on their feet (Weeks and Kestin, 1994). It has been shown for wild birds that the frequency of visits to a food source relate to the cost of reaching it (Kacelnik, 1984). We recently reported (Weeks and Davies, 1996) that this appeared to apply to lame broilers which fed for approximately twice as long but half as frequently as their mobile contemporaries.

Cloning mammals from somatic cells by nuclear transfer has the potential to assist with the preservation of genetic diversity. An increasing number of species have been successfully cloned by this approach; however, present methods are inefficient with few cloned embryos resulting in healthy offspring. In those livestock species that have already been cloned, it is clearly feasible to use cloning to preserve endangered breeds (e.g. the last surviving Enderby Island cow). The opportunity exists to recover oocytes from these cloned heifers and use frozen Enderby Island sperm from deceased bulls for in vitro fertilisation and thus, expand the genetic diversity of this breed. Where there exists an adequate understanding of the reproductive biology and embryology of the species concerned and adequate sources of females to supply both recipient oocytes and surrogates to gestate the pregnancies, intra-specific nuclear transfer and embryo transfer can be utilised. However, when these requirements cannot be met, as is common for most endangered species, cloning technology invariably involves the use of inter-species nuclear transfer and embryo transfer. Even in intra-specific cloning the source of oocyte for nuclear transfer is an important consideration. Typically, cloned animals are only genomic copies of the founder if they possess mitochondrial DNA which differs from the original animal. Different maternal lineages of oocytes both within and between breeds significantly affect cloning efficiency and livestock production characteristics. Cloning should not distract conservation efforts from encouraging the use of indigenous livestock breeds with traits of adaptation to local environments, the preservation of wildlife habitats or the use of other forms of assisted reproduction. Whilst it is often difficult to justify cloning in animal conservation at present, the appropriate cryo-preservation of tissues and cells from a wide selection of biodiversity is of paramount importance. This provides an insurance against further losses of genetic variation from dwindling populations, disease epidemics or even possible extinction. It would also complement the gene banking of gametes or embryos and can be performed more easily and cheaply. Future cloning from preserved somatic cells can reintroduce lost genes back into the breeding pool. With greater appreciation of the heritable attributes of traditional livestock breeds there is the desire to identify superior animals within these local populations and the genetic loci involved. Through clonal family performance testing, nuclear transfer can aid the selection of desirable genotypes and then the production of larger numbers of embryos or animals for natural breeding to more widely disseminate the desirable traits. With the identification of alleles conferring desirable attributes, transgenesis could be utilised to both improve traditional and industrial livestock breeds. This further emphasizes the importance of preserving global farm animal genetic resources.

Energy balance is a function of dry-matter intake (DMI), live weight and milk yield over a certain time period. To investigate potential strategies to use genetic selection for the improvement of the negative energy balance, genetic co-variances were estimated among DMI, live weight and milk yield during the first 15 weeks of lactation (no.=628). Rather than estimating the full 45 by 45 matrix a random regression model was used to estimate a second order covariance functions for the additive genetic and permanent environmental effects. Fixed effects were test-day, a group effect and week in lactation. Estimates for the genetic covariance function demonstrated that a high level of milk yield is only moderately correlated with a high level of DMI (0.21) but very strongly correlated to an increase of intake (0.97) and a loss of live weight (-0.46) during the first 15 weeks of lactation. Levels of weight and intake were correlated strongly (0.81). Estimates for the genetic correlations between weeks 1 and 15 were 0.79, 0.34 and 0.83 for milk yield, DMI and live weight respectively. DMI during early lactation was negatively correlated with milk yield but DMI during the later weeks was positively correlated with milk yield. The implication is that when selection is for a linear combination of milk yield, DMI and live weight (i.e. energy balance or efficiency) the moment in lactation of measuring each trait on the cow is of importance

Irrespective of whether farm animals are given access to a single homogeneous food or to two or more heterogeneous foods as a choice, their feeding behaviour raises one of two questions (i) how much to eat, and (ii) what to eat? Despite frequent comment to the contrary, their feeding behaviour appears to be goal-orientated rather than random or purposeless. I therefore consider first the goals of farm animals in relation to their feeding behaviour. In general it is accepted that the overall biological framework in which all animals are trying to maximize fitness’ also applies to farm animals. However, some modification is called for in order to account for those situations in which intensive genetic selection has led to relatively ‘unfit’ reproducing animals and for those cases where animals are given access to foods which have not figured in their evolution

On the basis that feeding behaviour is goal orientated, I then consider whether farm animals achieve their goals by monitoring their behaviour in the short or longer term. The conclusion drawn is that while short-term feeding behaviour may be a device to exploit the feeding environment effectively, it is largely unrelated to short-term fluctuations in an animal’s internal state. By contrast, longer-term feeding behaviour is very closely related to longer-term change in internal state, implying the maintenance of close control over feeding behaviour in terms of food intake and diet selection. All animals, including farm animals, are considered to be creatures of habit which maintain habitual feeding behaviour until a change is provoked by a significant alteration in their internal state. Such an alteration requires to be of significantly large magnitude and to be unlike the usual short-term, systematic fluctuations which occur over a day in the profiles of metabolites or hormones. Based on this premise, I contend that the mechanisms by which these disturbances are perceived by the animal will be general rather than specific. The notion that animals can fully achieve their goals by monitoring their feeding behaviour is obviously applicable in situations where they are given appropriate nutritional choices. Where animals are given inadequate or inappropriate choices, as is predominantly the case with farm animals, their feeding behaviour is designed to bring them as close as possible to their goals. Finally I consider the relevance of nutritional choices to farm animals by addressing the possibility of exploiting the goal orientation of feeding behaviour. I conclude that greater recognition of the goal-orientated nature of farm animals’ feeding behaviour can bring benefits in three areas: (i) improved biological understanding of animals’ goals; (ii) improved animal welfare; and (iii) improved animal performance.

In most experiments in which the influence of forage to concentrate ratios on milk quality have been examined, the composition of the forage has been incidental to the purpose of the trial. Legumes have resulted in higher yields of milk than grasses of similar digestibility. However, these increases were a reflexion of higher outputs of protein and lactose, since the feeding of legumes resulted in lower contents of milk fat. Changes in the digestibility of forage have shown considerable variability in response, in terms of the concentration of milk solids. However, an increase in digestibility of forage has not resulted in decreases in the yield of fat and, further, the yield of protein has been increased.

There is no indication that there is a requirement for ‘long hay’ to maintain milk quality and that a reduction in the chop length of silage has any influence on milk composition. However, the fine grinding of grass, which was the sole forage component of the diet, has caused a marked decrease in milk fat content. This effect was not apparent when finely ground and pelleted dried grass was used as a supplement but only in ad libitum feeding regimes.

Attempts to increase the content of milk fat in May and June by the supplementation of grazed grass with small quantities of hay have had little influence on milk yield and fat content. A much greater effect was observed when grazing was restricted and silage offered ad libitum overnight. The increase in fat content may be overcome by a reduction in milk and protein yield.

In general, the changes in milk composition have been small and this is likely to be a result of the high proportion of forage in the diets examined. The quantification of response in yield and content of fat and protein to changes in forage composition requires a change in approach. More emphasis should be given to the examination of the interaction between level or type of concentrate and the composition of the forage. Further, these trials should be accompanied by experiments to examine the effects of the dietary changes on the end products of digestion.

The lactating sow requires 5 to 7 kg food daily if it is to maintain body weight and condition in lactation but even on ad libitum intake sows fail to achieve the required food consumption and so lose both weight and tissue. The problem is most acute in primiparous sows and low lactation food intake is recognized as a major factor in post-weaning anoestrus and impaired reproductive performance. Studies of sows from the Moorepark herd are reported. Older animals, those with high suckling load and thin animals all tend to eat more with maximum daily intake occurring at 4 to 5 weeks of lactation. Although intake reduces at high environmental temperatures, this has been alleviated by wet feeding, offering a high energy-density diet or a high-protein diet. Other factors observed to influence voluntary food intake are breed, lighting pattern, dietary calcium and phosphorus levels.

This paper considers the welfare implications of breeding, feeding and managing dairy cows for increased productivity. The physiological demands of lactation for the high genetic merit dairy cow are exceptional, less in their intensity and more in their duration. Most welfare problems can be attributed less to productivity per se than to systems of feeding, milking and management that are unsuitable to the genotype of the high yielding cow. These include the inadequacies of wet grass silage as a staple food and the abnormal restriction of cows to twice-daily milking. It is also necessary to consider welfare problems that may arise from the application of new technologies to increase milk yield or to increase the rate of genetic progress. These may be related to the process itself or to its consequences. It is proposed that the commercial exploitation of these new technologies should be controlled by legislation similar to that for the protection of animals used for scientific purposes which applies a cost-benefit analysis to determine whether the cost to the animal can be justified in terms of any potential benefit to society.

Although a relatively young science, farm animal ethology has a considerable contribution to make to the development of housing systems. Two areas are highlighted in this review. First, the evaluation of existing housing systems is exemplified by studies of the effects of close confinement on sows. From such studies it has been concluded that close confinement can cause distress in sows. Secondly, the development of new housing systems is exemplified by studies on how pen design can control aggression.

The prolific ewe can be regarded as a valuable asset only if she produces viable lambs and, at the same time, sufficient colostrum to meet their needs for energy (MJ) and immunoglobulin (Ig) in the first days of life.

The energy requirements of the lamb will depend on its weight and the climatic conditions of its surroundings. Mellor and Murray (1986) recommend 180 ml colostrum per kg body weight during the first 18 h of life for lambs born indoors and 210 ml/kg body weight for lambs born in field conditions. The Ig requirement of the lamb will depend on its size and the disease challenge of the environment into which it is born.

Although lower immunoglobulin G (IgG) levels have been recorded in dead lambs compared with live lambs (Halliday, 1968 and 1978; Khalaf, Doxey, Baxter, Black, FitzSimons and Ferguson, 1979), it has been shown that many lambs having low serum IgG levels do survive (Halliday, 1974) and some with high levels die (Halliday, 1978).

The minimum intake of colostrum required for passive immunity is not known, but it is probably considerably less than that needed to meet the energy requirements (Mellor and Murray, 1986). Spedding, Treacher and Penning (1970) showed that as little as 8 g colostrum per kg lamb birth weight can provide protection from disease. Under poor conditions of hygiene this would probably not be sufficient. It thus seems likely that provided that the energy requirement of the lamb is met by feeding it colostrum, the Ig requirement will also be met.

The first study was conducted to investigate the possible relationship between milk urea concentrations and pregnancy rate in dairy cows. A total of 173 dairy cows were used in the study. They had not experienced reproductive problems post partum, however they were treated for suboestrus between 60 to 90 d post partum with either PGF2α or GnRH, PGF2α and GnRH. Suboestrus cows were studied in this experiment in order to see whether, when ovulation is initiated, high milk urea concentrations were associated with a poorer response to treatment. Milk samples were collected on the day of AI, for the measurement of urea concentrations, and pregnancy diagnosis was performed by the assay of Pregnancy Specific Protein Binding (PSPB) 50 d post-AI. Peak milk production (P=0.06), the type of diet (P=0.05), the main forage type (P=0.07) and the concentrate distribution system (P=0.03) influenced milk urea concentrations. There was no difference in the concentrations of urea in the milk of pregnant and non-pregnant cows (P = 0.33, 0.25 g L-1 vs. 0.27 g L-1, respectively). Pregnancy rate was not influenced by the type of suboestrus treatment used. A second experiment showed that there was a linear relationship between milk urea concentrations measured by a dipstick method (Azotest) and a laboratory method (r=0.51, P<0.001, n=89)

The resumption of reproductive activity in the early post partum period and the subsequent fertility of dairy cows are of considerable practical and economic importance to the producer. Regular milk progesterone analysis was used in this study to monitor the re-establishment of reproductive cyclicity in animals of average (AGM, n=20) and high genetic merit (HGM, n=28) kept under standard management conditions. The profiles obtained were then characterised into normal and four different types of abnormal activity. Resumption of cycles occurred significantly later in the higher yielding cows than in those of average genetic merit (23 ±2.3 days in HGM cows and 15 ± 1.6 days in AGM cows; P=0.0089). There was a significant increase in the amount of abnormal cycles encountered in the high genetic merit animals compared with average yielding animals (61% and 30% respectively; χ2 test, P=0.045); in particular, the delayed occurrence of ovulation post partum (11% vs 0%) and an increased incidence of persistent corpora lutea (32% vs 20%). For high genetic merit animals, the incidence of abnormal cycles was associated with increased peak milkyields (abnormal cycles: peak milk yield 54.7 ± 1.11 kg/day; normal cycles: peak milk yield 46.4 ± 1.35 kg/day, P=0.002). This relationship was not apparent in average genetic merit animals. First service conception rates were 50% (9/18) for AGM cows and 38% (10/26) for HGM cows (χ2 test, n.s.). The calving to conception interval was 98 ± 9.7 days for AGM animals (n=l7) and 105 ± 9.1 days for HGMs (n=24) (t-test, n.s.). In conclusion, this study confirms that high genetic merit dairy cows have compromised reproductive function in terms of a delayed resumption of cyclicity and an increased incidence of abnormal progesterone cycles, which was associated with higher peak milk yields. There was also a reduced first service conception rate in high yielders although the difference was not significant with this group size.

Gas production from the in vitro digestion of forage with buffered rumen fluid can be measured and used to determine forage digestibility and fermentation kinetics. Rumen micro-organisms ferment carbohydrate to gases (CO2 and CH4) and volatile fatty acids (VFA). The VFA produced also cause CO2 to be released from the C02-bicarbonate buffer. Theodorou et al. (1994) introduced the principle of measuring gas production by pressure increase using an electronic pressure transducer and sealed gas-tight culture bottles. Gases accumulate in the head space of the culture bottles as fermentation proceeds. The gas is measured and then released at regular intervals throughout the fermentation. This procedure was automated (Davies et al., 1995). The automated pressure evaluation system (APES) has advantages over the manual pressure transducer technique (Theodorou et al., 1994) in that it is less labour intensive and has been shown to be more sensitive to food characteristics (Davies et al., 1995). The APES, used in this work, has been improved to include new switches and a filtering system. It has been used here to determine the fermentation characteristics of various ruminant foods: ryegrass, wheat grain and ryegrass silage.