Energy is a major currency and resource in ecological systems. It is essential that the energy flows in such systems are understood for effective control of the production of livestock. With growing, lactating or pregnant cattle the farmer is faced with the problem of feeding to give optimum results. He needs to be able to predict the effects of feed quality, quantity and its distribution in time. Central to this problem is the prediction of how energy is used by the cow, for the competing processes of growth, lactation and pregnancy. The purpose of this paper is to introduce a deterministic model, NOSCOW, of the bioenergetic system for lactating, and pregnant, cattle. The model uses the recommendations of ARC (1980) as a base but includes the key ideas of potentials for lactation and growth. Twelve input factors are required by the model. The output is a time series with a weekly time step.

Two data sets have been used to evaluate NOSCOW, a model of the energy system of cows which allows milk production and live-weight change to be predicted simultaneously from dietary energy intake (Bruce, Broadbent and Topps, 1984).

Black and White Danish Dairy Cows (SDM) were used by Østergaard (1979) to study concentrate feeding strategies. There were nine treatments which differed in the level and pattern of concentrates fed over the first 36 weeks of lactation. These treatments caused substantial differences in the levels and patterns of energy intake.

The Intestinal Immune System is obliged to recognise not only antigens associated with pathogenic organisms but also harmless dietary protein. Since chronic immune responses to these ubiquitous antigens present in food are likely to be harmful to normal intestinal function, regulatory mechanisms have evolved which reduce immune responses to such antigens to levels acceptable to the individual. It is essential to the effective working of these mechanisms that the introduction to new antigens should be gradual and not be associated with the sudden presentation of large amounts of a new dietary material. Modern intensive weaning methods pay scant attention to the needs of these immunoregulatory systems, and the resultant immune response may be the cause of the villous atrophy and crypt hyperplasia seen immediately after weaning and which are thought to precipitate post weaning E. coli diarrhoea.

In recent years there has been a general trend in the pig industry towards early weaning. A number of factors were responsible for this but perhaps the major reason was that of economic pressure dictating increasing sow productivity. Early weaning was putatively the means for the production of more piglets per sow per year. In Table 1 are presented data derived from the Meat and Livestock Commissions Pig Improvement Services over the years 1970-1983. This data illustrates the changing pattern of production. The indications are that this trend will continue.

Early weaning represents a critical period in the life of a piglet since it is an abrupt process which removes the piglet from the comfort of the mother and the ad libitum supply of feed which she provides. Although the age at which piglets are weaned is variable, economic pressures encourage weaning at an early age as a means of shortening the reproductive cycle of the sow and thus improving her output. If a system of early weaning is to be successful it must supply the correct nutrition, enhance the natural disease resistance and provide an environment which creates least thermoregulatory demand on the animal. In addition, it should minimise disease challenge and avoid stressors such as those caused by overcrowding and inappropriate structural surfaces.

Previous research suggests that the feeding stratagem employed during a particular stage of the reproductive cycle may evoke an immediate response and/or a more long-term response in reproductive performance. This trial was designed to investigate the effect of feed restriction during lactation on reproductive performance when lactation periods of 10 and 35 days were employed.

Eighty, second to fifth parity Large White x Landrace sows were used in the experiment. The sows were allocated on a parity and liveweight basis to one of the following four lactation treatments:-

1. 1) 35 day lactation; fed 7 kg/day of a standard proprietary diet during lactation

2. 2) 35 day lactation; fed 3 kg/day during lactation

3. 3) 10 day lactation; fed 7 kg/day during lactation

4. 4) or 10 day lactation; fed 3 kg/day during lactation.

All sows were then fed 3 kg/day during the weaning to remating interval and 2.2 kg/day throughout gestation. Creep feed was offered ad libitum to the litters of sows on treatments 1 and 2 from 10 days post partum. Liveweight and backfat (maximum shoulder, P2 and minimum loin) measurements were taken at regular intervals throughout the experimental period. Piglet weaning weights and subsequent birth weights were recorded.

The most effective basis for derivation of simple feeding rules to ensure sow productivity is still in question. Liveweight change has emerged from a long series of feeding experiments as being potentially adequate for the purpose, however this has not net with success in pig units in the face of unwillingness by commercial sow herd managers to regularly weigh their sows. The most likely contender as an alternative to sow weight change as a measure of effective sow feeding is body condition; especially the amount of fat carried on the back. Indeed, it may be that body condition is a better indicator than live weight of the propensity of a sow to breed. It is possible to envisage recommended guidelines for feed allowances based upon condition score, or, more objectively, from a simple ultrasonic measurement of backfat depth at P2. The immediate objective of the current experimentation was to arrive at simple statements of targets for condition score and backfat depths which might be indicative of adequate and cost-effective sow feeding.

Low level feeding during lactations of greater than thirty five days duration has been shown to result in an extended weaning to remating interval and a reduction in subsequent litter size. The aim of this experiment was to examine whether this effect was a consequence of a reduction in ovulation rate and/or increased embryo mortality following such treatment.

The Agricultural Research Council (1981) states the energy requiremnets for pregnant sows in terms of amounts needed per day to ensure specific net pregnancy weight gains for differing weights at service (Table 1.). An experiment was set up primarily to test the validity of these recommendations which were derived by factorial calculations and secondly to examine the relationship between condition (P2 measurement) and weight changes over the reproductive cycle.

Catabolism of the sows’ maternal body tissues which commonly occurs during lactation starts not at parturition but during the latter part of the preceding pregnancy. An experiment was conducted to study the response of sows to the same amount of feed distributed differently between pregnancy and lactation.

Two patterns of feed distribution taking account of the anabolic/catabolic change in late pregnancy were compared with a conventional system which makes the major change in feed level at parturition.

The paper sets out to stress that although marketing is often put forward as one of agriculture's weaknesses (or even failures) it is wrong to assume that good marketing is a panacea. It can in fact be argued that the emphasis on the importance and relevance of marketing in agriculture today is in the circumstances merely a natural development. The way ahead in milk marketing as much as agricultural marketing is for this development to continue gradually. Dramatic results should not be expected in the short terra but in time may be expected to contribute significantly to the survival of the dairy and agricultural industry in the UK.

The performance of crossbred progeny of Oxford, Texel, Texel-Oxford, Charollais, Charmoise and Meatlinc terminal sires, mated with crossbred ewes, were compared.

The comparisons took place at ABRO's lowland farm in Staffordshire from 1979–1981. The crossbred ewes were by various crossing sire breeds out of a Scottish Blackface stock. Three or four six month old rams of each breed were used in each year, but 9 Texel-Oxford rams were used in 1979 and 1980. Oxford rams were used only in 1981.

The generally accepted view is that, in sheep and cattle, plane of nutrition (as indicated by growth rate) can influence body composition; the higher the rate of gain the greater the fatness at a particular live or carcass weight. However, exceptions to this view can be found which demonstrate that the effective protein: energy ratio of the diet can exert a considerable influence on the composition of live weight gain. Unfortunately most studies which have considered the effects of growth rate on composition (either directly or as a consequence of some treatment which resulted in different growth rates) have described their animals in terms of chemically determined protein, fat, ash and water. To assess the potential economic impact of different growth rates on body composition and the distribution of fat throughout the body requires dissection data, describing the animal in terms of lean, bone and individual fat depots. In this experiment the dissected composition of 44 Hampshire Down x Mule ewe lambs was determined in animals which had followed planned growth paths involving periods of high (H) and low (L) growth.

The ARC Nutrient Requirement of Pigs (1981) has highlighted a shortage of information which would allow factorial estimates of chemical body composition to be related to physical carcase composition and commercial grading characteristics. The present study aimed to provide estimates of these relationships.

Data related to weights of total carcass lean (Le), total carcass fat (TF), subcutaneous fat (SF), intermuscular fat (IF), total carcass bone (B), whole body crude protein (P), Lipid (Li), Ash (A) and Water (W) and backfat depths (P2, L2, shouTder(sh)) of 231 Newcastle selected (S) and control (C) boars.

A knowledge of the chemical composition of the dairy cow is Important in interpreting the interacting influences of body reserves, diet and feed intake on milk production. An investigation has designed to obtain information from a representative sample of Friesian/Holstein cows at different stages of lactation, different ages, and of different yield potential. This information is expensive to collect due to the costs Involved in slaughtering and analysing dairy cows, especially if they are high yielding cows at peak production. The animals used in the investigation have therefore all been Planned culls with sixteen in the later stages of lactation with only three killed in early lactation. It is intended to continue this investigation for several years to obtain a comprehensive data set on the chemical composition of the dairy cow.

The halothane gene (HALn) has beneficial effects on lean yield, and adverse effects on stress susceptibility, meat quality and litter size. The gene appears additive for lean content, but largely recessive for halothane sensitivity and other traits. Manipulating the frequency of the gene can lead to a worthwhile improvement in performance. At present, complete elimination of the gene requires expensive test matings, and a cheap and accurate method is needed for detecting heterozygotes. Reaction to the muscle relaxant succinylcholine was therefore investigated as a possible method of distinguishing the heterozygote (Nn) from the normal homozygote (NN).

Pigs can be bred at 6 months of age. By this time it is possible for their dams to have two litter records (at 12 months and 18 months of age) on which selection for litter size can be based. Hence, a generation interval of one year for both males and females can be achieved. Ollivier (1974), has shown that this system maximizes the rates of response. The accuracy with which replacements are chosen can be increased further by including information from other relatives (dam and sire family) in a selection index.

Rising living standards and an increasing awareness of the health risks of a diet high in saturated fats have led to strong consumer discrimination against animal fats. Additionally the surplusses of animal products in Europe suggest that more attention should be paid to the inputs in animal production, rather than solely increasing output. Improving the efficiency of lean meat production is therefore an important consideration in all meat animal systems. In 1976 Fowler, Bichard and Pease proposed the ‘biological indices’ lean growth rate and lean food conversion as selection criteria in pigs. These traits may be estimated as the product of growth rate (GR) or food conversion efficiency (FCE), and in vivo estimates of killing out and carcass lean proportions. However, in cattle and sheep the relatively low coefficient of variation of estimated killing out and of lean proportions, means that the biological indices are frequently dominated by GR and FCE. In such cases there may be little difference in response from selection solely on GR and FCE (Simm, 1983). The objective of the present study was to derive economic selection indices for terminal sire beef breeds, which might give appropriate economic weighting to the components of efficient lean meat production.

There are few published studies on the genetics of body growth to maturity in sheep. Such information is required for choosing an optimal time of selection for body weight and to predict correlated responses to selection at all stages of an animal's lifetime. The data were derived from a randomly selected control flock of Scottish Blackface sheep on a hard heather hill research farm in Peeblesshire, Scotland. The objectives of the analysis were to estimate the heritability of body weight at various ages between birth and maturity, and the genetic correlations between these weights.

The growth and carcase development of Angus -, Charolais -, Hereford - and Limousin cross yearling steers out of Hereford x Friesian cows, each fed to grow at three levels of daily gain during winter finishing and slaughtered at tree levels of estimated subcutaneous fat percentage (SFe) was investigated in a two year trial involving 240 animals (Table 1). Within each breed and year the two steers which had the extreme weights, and one of average weight were slaughtered at the start of the trial (ISG). The remaining 27 animals were allocated randomly amongst equal weight groups to the nine treatments.