A total of 74 pigs representing three commercially available crossbred types, Landrace (50%), Pietrain (50%) and Meishan (25%), were given food ad libitum over a 25- to 115-kg growth period and serially slaughtered for physical and chemical analysis in five groups at 32, 42, 63, 82 and 114 kg live weight (W). Results are presented in the order of pig type as above. Pig types grew at similar overall rates of live body gain, but the Meishan type ate more food and had greater back fat depth. The Pietrain type was least fat. Dissected fatty tissue grew substantially faster than the carcass as a whole; allometric exponents being 1·64, 1·34 and 1·52 (P < 0·05) for the Landrace, Pietrain and Meishan types respectively. Dissected lean tissue gains were 0·419, 0·427 and 0·308 kg daily (P < 0·01), and dissected fatty tissue gains were 0·251, 0·158 and 0·218 kg daily (P < 0·05); the Meishan type being slowest for lean gain and the Pietrain type slowest for fatty tissue gain. The Pietrain type had the largest cross-sectional area of the longissimus dorsi muscle, and the Meishan type the smallest. The pelvic limb of the Meishan type lost density (as measured by specific gravity) fastest, and that of the Pietrain slowest as the pigs grew. The Meishan type had a lower proportion of its carcass lean and a higher proportion of its carcass fat in the pelvic limb than did the other two types. For each kg of live-weight gain, 0·037, 0·041 and 0·032 kg (P < 0·05) of chemical protein was deposited in the pelvic limb of the three types respectively. Equivalent values for chemical lipid were 0·041, 0·035 and 0·041 (P < 0·05). The Meishan type retained protein at a relatively slower rate in the pelvic limb than in the body as a whole. The Pietrain type had the greatest ultimate protein mass in the pelvic limb. Estimation of whole body protein content as a linear function of pig live weight gives coefficients of 0·154, 0·178 and 0·168 kg (P < 0·05) for the three types respectively. Equivalent values for whole body lipid content were 0·269, 0·214 and 0·274 (P < 0·05). Best estimates of the daily rates of protein retention in the body of the whole live pig were 0·152, 0·197 and 0·142 kg/day for the Landrace, Pietrain and Meishan types respectively.

A review of work reported in the literature was used to present quantitative descriptions of protein use in the growing pig. These are detailed in the text, which also points to preferred values, and to anomalies and lacunae. The review was prepared with the objective of allowing from its content the inclusive and quantitative modelling of amino acid requirement. Requirement was approached as the sum of the component factors: maintenance and protein retention. Ileal true digestible protein and amino acid requirements are presented in a form consistent with that forwarded for energy. Thus both energy and protein elements can be conceptualized within a single coherent framework. Priority uses for absorbed amino acids were assumed to be (a) to support endogenous protein losses resultant from the passage of food and incomplete re-absorption prior to the terminal ileum, (b) to replace lost hair and skin, and (c) to cover the basic maintenance losses which will occur as a result of minimal protein turn-over even when protein retention is zero. The bulk of the protein requirement was directly linked to the daily rate of protein retention, for which the linear-plateau response was accepted. For determination of the maximum rate of protein retention the Gompertz function was proposed, although the use of a single value throughout the growth period was not dismissed. The balance of amino acids for protein retention is specified as different from that for maintenance. Central to the approach was the proposal that the inefficiency of use of ileal digested ideal protein, even when not supplied in excess, was an expression of protein losses occurring as a result of protein turn-over. The requirement for the satisfaction of the losses from protein turn-over occurring as a consequence of protein retention, and therefore additional to the requirements for maintenance, was identified. Quantification was attempted with sufficient success to warrant its inclusion into requirement estimation. It was concluded that this element addressed previously inadequately explained protein utilization inefficiencies. Algorithms are presented based upon protein turn-over which appear to be consistent with empirical findings.

Various types of computerised feed intake recording systems are used by research centres and breeding companies to monitor the individual food intake of pigs kept in groups. Most are single-spaced, allowing only one animal to feed at any one time, and they differ mainly in the design of the entrance and the level of protection offered to the feeding pig. The aim of the present experiment was to investigate the effect of single-space feeder entrance design on the performance and feeding behaviour of growing pigs by using designs offering three levels of protection.

A test of the theory that animals seek to eat what they need, is to offer them a choice of two feeds with different protein contents but similar energy yields. The animals, treated in this way, are expected to eat that combination of the two feeds which Just meets their protein and energy requirements. However, in a previous experiment (Kyriazakis, Emmans and Whittemore, 1987), when pigs were offered a choice between two feeds, a high variation in the choices of individuals was observed. This was attributed to the need for an initial learning period, where animals obtain information about the feeds before making “correct choices”. The purpose of this experiment was to compare different ways of giving the opportunity to the animals to learn about the feeds on offer, and to measure their effects on the diets selected by young pigs given choices between the same pair of feeds.

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).

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).

On a single feed an animal can increase its intake of a nutrient (eg. protein), as its ratio to energy is reduced, only by increasing its rate of energy intake. When given, as a choice, two feeds of a different protein but equal energy contents, it can vary its protein intake independently of Its energy intake by varying the proportion of each feed in its diet.

The experiment described here was designed to investigate the effect of feed protein content on the feed intake of young pigs and to test the proposition that young pigs, when given a choice between two feeds of different protein contents, a combination of which is non-limting, will select a diet which meets their protein requirements. In addition an investigation of the rules which govern the diet selection was carried out.

Four feeds (L, A, B and H) with similar energy contents (16.5 MJ DE per kg fresh feed) but different levels of crude protein (CP) were formulated and made into pellets. All feeds were intended to be non-limiting in vitamins and minerals.

Weight gains can occur with substantial fat losses and therefore liveweight change is unlikely to form the basis of feeding strategies, whereas the fatness of the animal may be a more appropriate criterion. Eighty Large White x Landrace gilts were first mated at 123.5 kg ± 1.54 with a P2 of 14.5 mm ± 0.24 [Meritronics] and 12.7 mm ± 0.19 (Vetscan]. Half these gilts were fed to be fat [F] at parturition [target 20-24 mm P2) and half were fed to be thin [T] [target 10-14 mm P2). F gilts consumed more feed during pregnancy and gained more weight and backfat than T gilts [all differences between the 2 treatments were significant P˂0.001). The number of piglets born and the number of live births were not affected by feeding gilts to be fat or thin, but fat gilts produced significantly heavier piglets. After parturition, half of both F and T gilts were offered either 7 kg of food per day [H] or 3 kg per day [L] and half were sucked by litters of 5 piglets and half by litters of 10 piglets during a 28 day lactation. Piglets were not given creep feed. Fatness of the gilts at parturition, feed level during lactation and sucking litter size all significantly influenced both the absolute and the change in liveweight and backfat from farrowing to weaning. Weight and P2 changes are shown in Figures 1 and 2. The performance of the litter was also significantly affected by the fatness of the gilt at parturition and by the number of piglets sucking. Results for each treatment group are given in Table 1. Animals offered the high level of feed during lactation had a significantly shorter interval between weaning and conception. There were also positive relationships between readiness to rebreed and absolute liveweight and absolute fatness.

Without knowledge of potential protein growth, nutrient requirements of pigs cannot be accurately determined. Daily protein retention [Pr] was estimated with 45 crossbred pigs serially slaughtered between 20 and 200 kg body weight. An understanding of growth to maturity is vital for the adequate nutrition of pigs grown to slaughter at heavier weights and for breeding sows, but the determined function: Pr(kg) - 0.125 [±0.009] -0.0002 [±0.0001] mean live weight, having no significant slope, was an inadequate descriptor of instantaneous Pr for pigs of more than 110 kg. Allometry was therefore used to predict protein weight at any given body weight and the Gompertz function to express body weight changes with time and derive values for weight at maturity. Predicted values for Pr attained maxima at 75 kg body weight of 130 g for entire males. 120 g for females and 105 g for castrates. Between 45 and 110 kg body weight Pr was within 10 g of the maximum rate (Figure 1); mature body weights were estimated to be 240, 215 and 225 kg. Allometric expressions for dissected carcass and chemical components as a function of empty body weight are given in Table 1. Figure 2 compares currently predicted potential rates of protein retention with those of Carr et al. [1977] and Thorbek (19751. It is evident that weight and age at maturity are crucial to the quantification of protein growth; such measurements are prerequisite to the provision of a quantitative description of improved pig genotypes.

The experiment described here was designed to test the proposition that growing pigs can control their overall intake of protein: on a feed with a low level of crude protein (CP) by increasing their daily feed intake (up to a limit) and, given a choice of two feeds with different levels of CP, by selecting a diet with optimal protein content.

The fatness (lipid weight at a given liveweight) of a given kind of pig can be varied by feeding. An energy restriction will reduce fatness and a feed of low protein:energy ratio will increase it. Pigs made thin by an energy restriction show “compensatory fattening” when returned to ad libitum feeding. The experiment described here had two purposes: (i) to test if pigs made fat would subsequently show “compensatory thinning” when given a feed of high proteimenergy ratio; it was expected that they would, (ii) To test if pigs would show compensatory protein growth following a period of low protein intake; it was expected that they would not.

The nature of compensatory growth in pigs remains unclear. But should pigs have undergone a period of growth retardation after weaning be capable of enhanced utilisation of food fed at the same level as their unretarded contemporaries, then exploiting the phenomenon would appear attractive to producers. Compensatory growth defined in this way is illustrated in Fig. 1.

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.

Over 95% of laying fowls in the UK are now housed in conventional battery cages. In recent years the general public and more specifically an Agricultural Committee on Animal Welfare in Poultry (1981) have raised doubts concerning the welfare of hens maintained this way and have called for further studies on alternative systems.

Consequently investigations into three alternatives to battery cages have been initiated: a range and covered strawyard system at The West of Scotland Agricultural College and a modified deep litter system at The East of Scotland College of Agriculture. The main objective of these investigations is to determine the practical feasibility and welfare consequences of the respective systems as alternatives to cages for keeping laying fowls. As well as recording productivity, the behavioural activities and distribution of wing-tagged birds have been monitored within the flocks of both the strawyard and deep litter systems. In all three studies ISA Brown layers were used and compared with sister stock housed in cages.

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.