Egg weight responses of laying hens fed different concentrations of vegetable oil and linoleic acid

Abstract

The relationships between dietary fat content and dietary fatty acid composition and egg weight were investigated in two strains of laying hens. Six diets were fed in which the levels of readily absorbable fatty acids, including linoleic acid, were increased by the addition of up to 32.6 g kg-1 safflower oil. Two additional diets containing olive oil provided intermediate or high levels of readily absorbable fatty acids and a low level of linoleic acid. The diets were fed from 30 to 46 weeks of age (phase 1) and again from 54 to 70 weeks of age (phase 2) after an intermediate buffer period in which a diet low in both fat and linoleic acid was fed. The diets had no significant effect on feed intake, liveweight or egg mass output, although small differences in egg number occurred. Egg weight responded to increasing levels of safflower oil in the diet but not to similar levels of olive oil. These differences cannot be attributed to dietary energy or to the intake of nutrients other than those associated with the inclusion of vegetable oil. It is concluded that the linoleic acid component of safflower oil is responsible for the observed effects on egg weight. As judged by regression analyses the egg weight response was significant in only one strain, being linear in phase 1 and curvilinear in phase 2.