P. R. English

The effect of sex on growth and carcass quality in the bacon pig

Castration of males is a long-established practice in animal husbandry, and although the use of boars rather than hogs was advocated by Fitzherbert in 1534 the use of castrates in pig production has continued to the present day.

Protein, lysine and feed intake level effects on pig growth

A total of 512 pigs were given from 50 lb live weight one of 16 diets (four lysine levels at each of 12, 14, 16 and 18% protein), at one of four levels of intake. They were killed at 100, 150, 200 or 250 lb live weight and the carcasses jointed in a standard manner and right sides dissected into lean meat, fat, skin and bone. Mean percentage proportion of shoulder, middle and ham joints in the dressed sides at the four weights was 36·3, 36·4 and 27·3; 35·4, 37·9 and 26·7; 34·5, 39·6 and 25·9; and 33·8, 40·7 and 25·5, respectively. Mean percentage lean meat at the four live weights was 61·5, 59·9, 56·7 and 54·2 and the mean percentage fat was 20·7, 24·4, 29·4 and 32·8. Carcass quality was influenced significantly by dietary treatment and sex. Increasing the level of protein in the diet up to 16, 16, 14–16 and 14%, respectively, for the four live weight groups gave a significant increase in carcass leanness. Increasing the level of lysine in the diet did not have a very marked effect on carcass composition, while increasing feed intake to the highest level produced fatter carcasses at all weights. Carcasses of males were fatter and with a lower proportion of ham than those of females. Interactions involving dietary treatments and sex were described. Chemical composition of the m. longissimus dorsi was not altered markedly by dietary treatment or sex but dry matter and intramuscular fat content rose with increasing weight. Protein content of the dry matter remained fairly constant at all weights, while colour and shear value rose with increasing weight but were not significantly influenced by dietary treatment or sex. The pH values of the m. multifidus dorsi just after slaughter or on the day following were not markedly affected by dietary treatment, sex or weight.

Interrelationships between growth, gonadotrophin secretion and sexual maturation in gilts reared in different litter sizes

One gilt from each of 24 littermate trios was assigned at birth to one of three treatments which were to adjust litter size to six, nine or 12 piglets. Plasma luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were measured before and after stimulation with 1 ng gonadotrophin-releasing hormone (GnRH) per kg body weight at 55 and 140 days of age. At 150 days, oestrogen was administered and ovarian and uterine responses were measured at slaughter on day 160. Litter size significantly modified pre-weaning growth rate ( P P P P P P P Variations in family birth and litter weaning weights were negatively correlated with ovarian and uterine development ( P P Basal FSH and the responses of both LH and FSH to GnRH at 55 days were correlated with growth rate at day 55 ( P P

A note on dried poultry manure in the diet of the growing pig

Dried poultry manure, produced locally by sterilization and drying, was evaluated as an addition to a conventional diet, at levels of 10, 20 and 30%, for growing pigs from 23 to 85 kg live weight. The 32 pigs remained healthy and the dried manure had no apparent adverse effect on the carcasses. There were significant linear relationships between the amount of manure added to the conventional diet and growth rate, feed conversion efficiency and certain carcass characteristics. For every 10% addition of manure, growth was reduced by 0·02 kg/day, feed conversion efficiency by 0·25 units and killing-out percentage by 0·96. The dried manure contained about 30% crude protein and was a rich source of minerals.