The newborn lamb lacks circulating antibodies and relies on an early and adequate intake of colostrum for passive protection against disease and for energy (Black, Francis and Nicholls, 1985; Mellor, 1990). However, lambs may receive less colostrum than they require because of sibling competition, maternal undernutrition or udder disease. Colostrum insufficiency accounts for about 25% of perinatal lamb deaths world wide (Khalaf, Doxey and Baxter, 1979).

Powdered colostrum substitutes may be used to supplement ‘at risk’ lambs but, because the products are manufactured outside the United Kingdom (UK), mainly from bovine sources, their relevance to UK sheep enterprises is uncertain. Further, their available energy content is low because the main constituent, protein, is not catabolized by newborn lambs (Mellor and Cockburn, 1986). The present work measured the ability of one substitute derived from bovine whey (based on ProLAM, Fisons Animal Health Ltd), with or without supplementary glucose; to prevent disease and promote growth to 3 months in lambs reared in typical UK farm conditions.

Expressing the protein value of a food involves measurements of several of its characteristics. Many in vivo studies have shown, that the protein degradability in the rumen varies substantially both between and within foods and therefore estimation of protein degradability in the rumen is an important task in protein evaluation. The most common method used has been the in situ (in sacco, nylon bag) method but many in vitro methods have been introduced and are based on use of either buffer solubility, chemical methods, rumen fluid or enzymes. None of these in vitro methods has proven to be of general use. In further development of in vitro methods as well as the in situ method a major problem is lack of a set of samples with a ‘true’ in vivo degradability which can be used for calibration of alternative methods. Microbial protein synthesis in the rumen has to be related to food characteristics which can be analysed easily. In vitro methods which can predict organic matter digestibility in foods are available and can be used to predict microbial protein synthesis in the rumen. Intestinal digestibility of undegraded dietary protein varies substantially both between and within foods and easy methods to estimate intestinal digestibility are therefore essential. The mobile bag method is easy to use and seems to give reliable results on most foods but requires access to duodenal cannulated animals which prevents this method from being routine. Alternative in vitro methods have been developed but further research is required for validation of these methods on a wide range of foods before they can be accepted for general use.

Major increases in the rate of genetic improvement in the dairy herd have been obtained in the United Kingdom and the Republic of Ireland since the mid 1980s. The implications of increases in genetic merit and the possible consequences of genotype X nutrition interactions on the efficiency of milk production systems are reviewed. The majority of previous studies with dairy cattle of moderate genetic merit suggest little evidence of genotype X nutrition interactions across a range of nutritional and management regimes, with higher milk production of high merit cows largely accounted for by effects on nutrient partitioning. However, more recent results suggest a significant re-ranking of sires when evaluated under either intensive feeding systems or in systems with a high reliance on grazed pasture.

Under intensive feeding systems higher animal performance has been obtained with high merit cows across a range of concentrate inputs and feeding systems. However, recent results from the Langhill studies provide the first tentative evidence of a genotype X nutrition interaction, with significantly different regression coefficients between genetic merit (as assessed by pedigree index) and milk production, under either low or high forage diets. The implications of these results are that high merit cows may be unable to express their full genetic potential for milk production when offered a high forage (or low energy density) diet. Consequently, the influence of other factors which have a major effect on voluntary food intake, and hence nutrient intake, e.g. forage dry matter content and forage digestibility, may be relatively more important with high genetic merit dairy cows.

It is concluded that higher milk production in high merit cows is largely attributable to variation in partitioning of nutrients, rather than to changes in food intake or digestive efficiency. Consequently, it is important fully to assess the animal performance and welfare implications of maintaining high genetic merit dairy cows under systems which may limit nutrient intake, e.g. under high forage regimes involving a high reliance on grazed or conserved forage. The major challenge for research and dairy herd management is to increase food intake with grass- and/or grass silage-based diets, thereby reducing the need for high levels of concentrates input to prevent excessive body condition loss with high genetic merit dairy cows in early lactation.

In sacco studies are at present the most practical way of estimating the rumen degradability of feeds. The commonly adopted procedure (Standard Method = SM) has a number of disadvantages, including night work and the need to select bags at each sampling time. The Complete Exchange Method (CEM), described here, has been developed to meet the need for a convenient routine procedure.

When a food is ingested by a ruminant animal, the carbohydrate fraction of the food is fermented by the rumen micro-organisms to produce gas (predominantly carbon dioxide and methane) as well as volatile fatty acids (VFA). The gas production technique simulates this fermentation process and provides an estimate of both the rate and extent of fermentation. Comparing the gas production (GP) profiles of foods enables a comparison to be made of the fermentative characteristics of different foods. However, the technique uses a bicarbonate-based medium system with the rumen liquor. This complicates the GP profile because of the production of ‘indirect’ gas resulting from the reaction between the VFA and the bicarbonate ions.

Beuvink and Spoelstra (1992) measured the volume of gas produced from buffered rumen fluid when known amounts of VFA were added and observed that 20·8 ml gas were released per mmol VFA. However, there is variation between laboratories in terms of the composition of the medium that is used. Even when the same medium is used, significant differences have been observed in the GP profile when different types of apparatus were employed (Rymer and Givens, 1997). Media are gassed with carbon dioxide before they are added to the gas production system and it is possible that the concentration of carbon dioxide dissolved in the medium varies between experiments. The objective of this experiment, therefore, was to determine whether the volume of indirect gas produced was affected by the composition of the medium, the addition of carbon dioxide, and the technique employed to measure gas production.

The overall objective of a series of experiments to investigate ‘metabolic stress’ was to examine the relationships between ‘metabolic load’, disease and other parameters associated with the welfare of the dairy cow. In the main, these used several well controlled herd based studies complimented with more basic and strategic investigations. In this paper we compare and contrast practical aspects of health and welfare in two high genetic merit herds managed at the extremes of inputs and outputs for dairy farming in south-west Scotland. The hypothesis was that high output herds would have more health and welfare problems than low input herds. Two herds (70 Holstein-Friesian cows each) at SAC Acrehead Dumfries of a similar genetic background (overall in the top 5% of UK cows by PIN and ITEM), were housed in identical buildings and tended by the same herdsman. Both herds had autumn- and spring-calving cattle. The ‘low input’ herd (LI) was given a minimum of concentrate (approx. 0.5 t per cow per year) and milked twice a day and had a restricted quota of 385 000 l. The ‘high output’ herd (HO) was managed for high yields (unrestricted quota) and was given concentrates (2 t per cow per year) and forage ad libitum and milked three times daily. In 1995-96 the sole source of winter forage was grass/clover silage (LI) or grass silage (HO) but in 1996-1998 ensiled cereal and fodder beet were included in both diets. ‘Metabolic load’ could only be inferred from overall inputs, milk outputs, weight loss, body condition score and behaviour. There were significant differences in 305-day lactation yields between herds, and season of calving especially in 1995-96 (LI autumn; 5952 l at 30 g/kg protein (P); LI spring; 5741 l, 32.5 g/kg P; HO autumn; 9541 l at 32.8 g/kg P; HO spring; 8402 l, 32.6 g/kg P). LI weight and body condition-score losses were greatest in this year and behavioural studies showed substantial differences in feeding time (HO < LI, P < 0.05) and total lying time (LI < HO; P < 0.05). However these differences were much less marked in subsequent years. There was a significant difference in the prevalence and incidence of clinical lameness between herds (HO > LI; P < 0.05) and season (autumn > spring P < 0.05) but not for mastitis or metabolic disease. An in-depth study of subclinical claw horn lesion development in first calving heifers showed significant differences between herds in 1996-97 (LI > HO, P < 0.05) but none in 1995-96. There was a significant difference for season in both years (autumn > spring, P < 0.05). Analysis of blood biochemistry parameters of samples taken at approximately 1 month after calving showed some significant differences between LI and HO generally indicating a greater ‘metabolic load’ for LI. Although the full effects of ‘metabolic load’ on immune function and reproduction are dealt with elsewhere our preliminary data showed no significant differences between herds for the former but some significant differences for the latter, in particular there were differences in aspects of the progesterone profiles between herds and more importantly between seasons. However these latter differences were not clearly reflected in conception rates. It was concluded that the hypothesis was not fully sustained and that both systems had pitfalls in terms of welfare. The three major areas causing difficulties for both systems were the need first to ensure adequate intake of forage; secondly to limit the environmental challenge to the feet and udder and finally to marry these systems to the factors limiting reproduction, primarily calving season and ability of reproduction management.

In Ireland, surveys in the 1970's have shown calving rates to first service of 60-69%. Since then genetic merit and milk yield per cow have increased significantly. The objectives of this study were to determine calving rates in Irish dairy herds for the period 1991-1996 and if these had declined over time. Breeding records for 58 Spring calving commercial dairy herds maintained on the computerised DAIRYMIS System were analysed. Inseminations were categorised as either DIY AI (DIY), commercial AI (COM) or Natural Service (NAT). Between 1991 and 1996 there was a significant trend towards DIY (P<0.01) and away from NAT (P<0.01) with no consistent trend in COM usage. In 1991, roughly one third of services were to each of the three service methods but by 1996 DIY accounted for nearly 50% of all services. A subset of 34 herds, which had been present for at least five of the six years between 1991 and 1996, was used in the calving rate analysis. Calving rates to first service for DIY (48.4%) and NAT (46.0%) were not significantly different although both were significantly lower (P<0.001) than those for COM (54.5%). For small (<65), medium (65-128) and large herds (˃128) the respective proportion of services in each category were 22%, 44% and 34%. The respective calving rates of 55.2%, 51.6% and 45.7% declined significantly as herd size increased For all service types, there was a significant (P<0.001) decline in first service calving rate over time. The increased usage of DIY, combined with its lower fertility rates, would appear to be one factor responsible for the reduction in calving rate for 1991-1996 period.

From an animal production and welfare perspective, an important social choice made by farm animals is whether and how vigorously to fight others. The choice to fight (i.e. simultaneous escalated aggression by both contestants) may result in severe injury when unfamiliar animals first meet or compete for highly valued resources. Game theory models of aggressive interactions predict that animals have evolved to stop or avoid fighting when they assess their chances of winning a contest to be poor. Assessment may occur during or before a fight. If it occurs before a fight, reliable cues of fighting ability must exist. If farm animals can establish relative social status by assessment prior to fighting, it may be possible to construct social groups which contain individuals of differing abilities such that most disputes are resolved through assessment and levels of damaging aggression are kept low. Social status appears to be established by assessment rather than fighting in free-ranging deer and sheep when asymmetries exist in reliable cues of their fighting abilities such as roaring rate and horn size. However, there have been few detailed studies of other farmed species and findings are equivocal. Work on young pigs suggests that, in pair-wise encounters, individuals are unable to assess weight-related asymmetries in their abilities without fighting. However, recent studies of groups of pigs suggest that some form of assessment prior to fighting may occur. Individuals were classified as high (H) or low (L) aggressive on the basis of their behaviour in an attack latency test. When litters of H pigs were mixed with litters of L pigs, significantly fewer pairs of unfamiliar pigs fought than when newly mixed groups were made up of litters of H pigs only, or litters of L pigs only. Thus, fighting was least frequent when there was a marked asymmetry in the aggressiveness of unfamiliar individuals. Another study raised the possibility that H and L pigs may be following alternative strategies which, under certain circumstances, are similarly beneficial in welfare and production terms. Further work is required to substantiate these findings and to determine whether aggressiveness is a reliable cue of fighting ability and, if so, how it is manifest and assessed.

This paper reviews current knowledge on the feeding of fibrous foods to pigs. It attempts to explain why fibrous foods differ in their nutritional value by defining what constitutes ‘dietary fibre’ and by discussing aspects associated with digestion, absorption, fermentation and metabolism in the gastro-intestinal tract. Fibrous diets can contribute proportionately up to 0-3 of the energy requirements of the animal, but there are significant reductions in the digestibility of all nutrients. There is a reduction in energy intake with increase in fibre intake, and this reduces both growth and food utilization efficiency; carcasses may, however, be leaner. Sows are better able to utilize fibre than weaned or growing/ fattening pigs and there may be improvements in reproduction as well as health and welfare benefits. Nutritive values can be improved by processing and deficiencies overcome by the use of synthetic and other materials. There is considerable potential to incorporate fibrous and by-product materials into feeding strategies for pigs in developing countries, with both economic and productive advantages.

The dairy industry has continued to innovate to meet the needs of the consumers' specification of milk at a low price, of good hygienic quality and with rising expectations of animal welfare. The introduction of robotic milking offers the opportunity for the cost effective deployment of novel sensors for a variety of milk analytes. Traditional methods of monitoring health changes in animals are based entirely on the human senses. However, in modern milking systems humans rarely have enough time to see the cows to observe for signs of ill health, the extreme case is that of robotic milking. Novel sensors will allow closed loop control systems where the early detection of deviations from optimal performance will enable the farm manager to make management decisions before damage to potential milk yields is irreversible. Where a biological model already exists, for example, in the prediction of ovulation with milk progesterone analysis, rapid progress is being made towards an automated prediction system. Integrated management systems for dairy cows will not only have the traditional goals of efficient milk production but can also be tuned to reduce polluting outputs of ammonia, phosphorus and methane. The main metabolic markers in milk to be monitored are urea, fat, ketones and protein. The detection of mastitis can be achieved by the development of sensor systems to detect enzyme markers of inflammatory response such as Nagase. Multi-disciplinary research is needed to develop integrated management systems drawing all the different elements of dairy cow management into a single system. The major cause of death in dairy cows is dystocia and monitoring systems are needed to ensure that parturition is better managed.

The thermal components of the environment, through their effects on the animals' heat exchange, influence growth, metabolism and voluntary food intake. The environmental components considered include air temperature, either constant or fluctuating, air movement, relative humidity, group size, stocking density and atmospheric concentrations of various gases and dusts. For the growing pig, it has been calculated that each 1°C change in temperature is associated with a 0.65 MJ metabolizable energy (ME) per day change in energy intake; for the other environmental components the variation was between 0.36 and 0.65 MJ ME per day. From the relation between environmental temperatures, food intake and growth, it was shown that for young pigs the optimum temperature range was between 20 and 25°C; for older animals it was between 10 and 20°C. Knowledge of the extent to which food intake changes with the environmental circumstances, both cold and hot, allows feeding and managemental strategies to be developed to ensure optimum growth and efficiency of food utilization.

I am not sure what the organisers had in mind when they selected the title for this talk. To me it suggests that two components may contribute to the concentration of a metabolite - one determined by the flow of nutrients, derived either exogenously or endogenously, while a second is derived from what I propose to call ‘transitory phenomena’, that is, produced from some fleeting or transitory response - stress, human/animal interaction or a response to feeding as distinct from food. Presumably it is the first component which we would hope to relate in some way to animal production, and I propose to begin by seeing to what extent we find a close relation between flow and concentration for several blood constituents. I have used the term ‘flux’ to encompass conveniently what has variously been called ‘entry rate’, ‘turnover rate’ and ‘irreversible’ loss. These terms are not synonymous, but for the present discussion the distinctions are not important.

A large proportion of broiler chickens suffer from lameness euphemistically called ‘leg weakness’. In a survey of commercial, intensively reared broilers, 90% had a detectable gait abnormality and 26% suffered an abnormality of sufficient severity for their welfare to be compromised (Kestin et al., 1992). It is assumed that leg weakness is painful but there is little direct evidence of this. Chickens have been shown to be able to select an adequate protein diet from a choice of two or three foods which are individually inadequate (Forbes and Shariatmadari, 1994). Broiler chickens showed a significant preference for food of the colour which was paired with ascorbic acid supplementation when the requirement for ascorbic acid was increased by heat stress (Kutlu and Forbes, 1993).

This paper draws on a recent multi-donor study on livestock and the environment and highlights how its findings might impact on research agendas worldwide. The soaring demand for meat and milk puts great pressure on the global natural resource base. About one-quarter of the world's total land area is used for grazing livestock. In addition, about one-fifth of the world's arable land is used for growing cereals for livestock food. Livestock production is the world's largest land user and may soon he its most important agricultural activity in terms of economic output. Livestock produce 13 billion tons of waste each year. A large part of this is recycled but, where animal concentrations are high, waste poses an environmental hazard. Water, already scarce in many parts of the world, is required not only for animals' drinking but also to grow food crops and for waste disposal. Pollution of land and water is another concern as is the impact by livestock, directly or indirectly, on biodiversity. Greenhouse gases from livestock and livestock waste contribute to global warming.

The paper provides an overview of critical livestock environment interactions, so-called hotspots, notably the overgrazing/degradation issue, deforestation, the ‘involution’ of mixed farming systems and the waste problem in areas of high animal concentrations. Measures that tackle only the superficial effects of environmental damage will never be as effective as a policy which attacks the underlying causes. Those causes are often deeply entrenched in what has become an almost universal fact: those who gain benefits from over-exploitation and degradation of the environment have not paid the full cost. Incorporating the environmental cost into the price of livestock products is critical to achieving sustainable development. The technological opportunities, and, therefore, the scope, for increasing livestock production, while simultaneously reducing the use of natural resources per unit of product, are enormous. Research needs to be channelled to reflect real scarcities of natural resources while respecting the need to maintain and improve livelihoods.

The gas test is commonly described as a simple, rapid and cheap technique for predicting the energy value of forages but it requires animals fitted with a canula. In horses, this method can be implemented with caecal fluid as an inoculum to predict the organic matter digestibility (OMD) of forages (Macheboeuf et al., 1998). In the present work, as bacterial content of faeces was known to be very high (Meyer et al., 1993), the use of faeces as a source of inoculum for predicting OMD of forages in horses was studied.

Conjugated linoleic acids (CLA) are potent anticarcinogens secreted into the milk of ruminants. The present study was carried out to detect the post–ruminal effects of a duodenally infused commercial CLA product on milk–fat synthesis and fatty acid pattern in lactating cows. Four Holstein cows, fistulated with duodenal cannulae, were infused with 200 g of a CLA mixture daily into the duodenum over a period of 5 days (period II), while no application of CLA acted as controls in period I and III. In contrast to the marginal effect of the CLA application on milk yield, an obvious decrease of milk fat content of 40% was measured. The fat yield decreased during the infusion period to about half of the control period, whereas protein and lactose content in milk was not significantly influenced. The CLA percentage of milk fat increased sevenfold during infusion of the CLA supplement. The data demonstrate that duodenal infusion of CLA inhibits the milk fat synthesis, resulting in the decrease of milk fat content and fat yield. It can be concluded, that CLA supplements increase the CLA concentration in milk fat, which probably has to be rumen protected for oral administration.

Plant secondary metabolites (PSM) are widely known for their antinutritional properties; their excessive consumption can detrimentally affect herbivore health and, in some cases, survival. However, a growing body of evidence is suggesting that some classes of PSM may also have some positive effects on herbivores. Such positive effects include the antiparasitic properties of certain PSM and their beneficial consequences on the herbivore's fitness. One of the better-exploited classes of PSM that have been reported with anthelmintic properties is that of the condensed tannins. The consumption of moderate concentrations of condensed tannins has resulted in reduced level of parasitism in sheep and other ruminants. In this paper we discuss the conditions that should be met in order for the positive anthelmintic properties of PSM, and condensed tannins in particular, to be beneficial for parasitised sheep. We also examine whether PSM could have a role in controlling parasitism in ruminants and point out the future research needed to achieve an efficient use of PSM for parasite control.

Selection for meat production in poultry includes commercial development of meat-type chickens, turkeys and waterfowl and laboratory studies that involve these types of poultry. Heritabilities for growth traits are moderate to high, enabling response to selection for these traits. Changes in growth traits result in correlated responses in feed intake and have a negative relationship with reproductive traits. That is, deviations from intermediate growth rates are deleterious to reproduction. In this paper we discuss genetic aspects of poultry meat production and long-term laboratory selection experiments for growth. Emphasis is given to the species with the most extensive research base, the chicken.