Effect of nutrition in the rearing and laying phases on mortality and egg composition of crossbred layers.

Crossbred pullets reared on a low plane of nutrition had a lower mortality rate due to Marek's disease and lymphoid leucosis in the laying phase and had smaller livers with less fat than those reared on a high plane of nutrition. On the other hand, the addition of 0.06% methionine to the laying diet increased the incidence of deaths due to Marek's disease and lymphoid leucosis. The spleen weight of birds fed the diet supplemented with methionine was greater than that of those fed the unsupplemented diet. The source of cereals in the laying diet had no effect on mortality, but birds fed diets with barley had larger livers and spleens. The gizzards and intestinal tracts of the birds fed the diet with oats were larger than that of birds fed diets based on barley. The inclusion of 2.5% rapeseed oil in the laying diet resulted in haemorrhage of ovarian follicles and reduced the proportion of yolk in the egg.