No description available.

No description available.

This work aimed to (i) explore the consequences of some breed and feed choices on lamb growth and carcass composition, (ii) examine changes in carcass quality traits during growth in meat sheep, (iii) identify ways in which CT scanning information can be used to measure carcass quality traits in meat sheep, and (iv) optimise two stage selection strategies for incorporating CT scanning into breeding programmes for meat sheep. Consequences of some breed and feed choices on lamb growth and carcass composition were explored using experimental data where growth rate and carcass composition had been measured at various stages of maturity in lambs of different genotypes (Suffolk and Scottish Blackface and their cross) in different nutritional environments (different dried, pelleted forages indoors and different swards outdoors). Lambs fed indoors on dried Ryegrass or dried Lucerne showed no genotype of diet effects on carcass composition. However, lambs on Ryegrass had lower intakes (0.878 as great) and slower growth (0.851 as fast) than those on Lucerne. Genotype effects on geed intake and growth rate were related to mature size differences. When lambs were grazing different swards outdoors, sward type did not affect carcass composition at any stage of maturity. At 0.30 mature weight, genotype differences in carcass composition were small but by 0.45 mature weight, Scottish Blackface lambs had less fat (0.749 as much), more lean (1.065 as much) and more bone (1.055) as much) than did Suffolk lambs. Genotype by sward interactions existed for growth rate, Suffolk lambs having higher growth rates than Scottish Blackface lambs on Clover but not on Rye grass. Growth rate declined to a greater extent in Suffolk than Scottish Blackface lambs as nutritional environment became worse; that is, Suffolk lambs expressing greater environmental sensitivity than the Scottish Blackface. Carcass composition, tissue distribution and fat partitioning, and the way in which these attributes changed with growth in live weight, were studied in three breeds of terminal sire sheep. Data used were from 160 lambs from a serial slaughter and dissection trial. Texel lambs, at similar live weights, were leaner than Suffolk or Charollais lambs but any differences in tissue distribution and fat partitioning were small. Proportion of carcass weight and lean contained in the higher priced joints declined while intramuscular fat content increased with growth in live weight. Lambs became fatter overall, with partitioning of carcass fat tending more towards the subcutaneous depot, with growth in live weight.

No description available.

No description available.

Piglet-weaning mortality is an enduring problem for the pig industry but is likely to be strongly influenced by the maternal behaviour and overall rearing ability, of the sow. Farrowing crates are the most common method of housing lactating sows in this and many other countries. However, farrowing crates pose a welfare dilemma: they are aversive for sows prior to parturition but limit the number of piglet crushing mortalities. One solution to this dilemma would be to breed sows better adapted to the crate system. To this end, a longitudinal breed study was set up that observed the behaviour of individual sows over their first two parities, in farrowing crates both with and without straw. Consistent behavioural traits are identified, most notably sow-piglet interactions and posture changing, and genetic influences are inferred from breed differences. The mean number of still-births and crushing mortalities per litter are modelled for non-behavioural influences. Season and litter size feature strongly for both these models. The behavioural characteristics of crushing and savaging sows are described and discussed in relation to functional explanations and possible causal mechanisms. An argument is developed that identifies piglet-savaging behaviour with being hypersensitive to restriction during pre-farrowing nest-building, resulting in physiological changes influencing the progress of parturition. Sows possess behavioural mechanisms to reduce the risk of crushing, which are modified by the farrowing crate in both positive and negative ways.

No description available.

Experiments were conducted to determine the importance of progesterone in egg production. Plasma levels of progesterone were found to be higher in laying birds than in immature or non-laying females. In the laying hen, progesterone is produced chiefly by the mature ovarian follicle before it ovulates, and this triggers the pre-ovulatory discharge of luteinizing hormone (LH). Egg production was observed to decline in the first twelve months of lay in three strains of hen examined (2 egg-producing strains; 1 broiler breeder strain) and this decline is partly due to birds laying shorter sequences of eggs, but the range of times in which egg-laying normally occurs each day did not vary with the age of the hen. The onset of lay was concomitant with an increase in progesterone secretion, but the rates of lay of the 3 different strains in the first year of egg production was not correlated with progesterone secretion. However, a direct correlation with basal plasma LH levels was observed. Neither the sensitivity of the pituitary to LH-RH nor the sensitivity of the ovary to ovine LH was different in young, high producing hens or old, lower producing hens but a decline in the sensitivity of the CNS mechanism regulating the pre-ovulatory release of LH was noted in older hens. The follicular structure of the ovary was not different in high and low ovulating strains of hen, but age-related changes were observed. Older birds tended to have fewer follicles developing at a time, and this was thought to be one reason why egg production declines with age. Hens laying at very low rates had essentially normal ovaries and it was the failure of many follicles to reach the outside world in fully-formed eggs which was an important cause of low production in these hens.

This program of work was undertaken to obtain information on the effect of food deprivation on sheep in terms of changes in behaviour, blood biochemistry and feeding motivation. Chapter 2 investigates the behavioural responses of sheep to food deprivation of up to 24h. Changes in behaviour during deprivation suggest that sheep were actively seeking food. Chapter 3 investigated the effect of elevated temperature on the behaviour and physiology of sheep deprived of food for 24h at space allowances similar to those used for the commercial transportation of sheep. Evidence of fasting was found during treatment. Post-treatment there was an increase in feeding and evidence that the sheep became dehydrated as they fed. Chapters 4, 5 and 6 investigated three aspects of transport, the provision of a period of lairage during a journey, and the effects of familiarity of post-transport housing and an additional period of food deprivation following a journey on the behavioural responses of sheep. The provision of a period of lairage facilitated post-treatment recovery, reducing the changes in liveweight during the treatment period and shortening the length of time for behaviour to return to pre-treatment levels. Changes in diet and environment post-transport were found to affect the behaviour of the sheep. Withholding food after 15h transport was associated with an increase in food-seeking behaviour which decreased after food was provided. Chapter 7 investigated the feeding motivation of sheep after 6h-24h without food. There was an increase in feeding motivation after 6h without food which was reduced by providing food.

No description available.