The Relation of Obesity to Egg Production in Broiler Breeders

ABSTRACT Two experiments were conducted to investigate the effect of carcass fat on egg production in broiler breeder hens. Two groups of birds were brought into production at the same time (after a similar period of delay) but with widely different levels of carcass fat. This was accomplished by subjecting one group to restricted dietary energy and increasing daylength and the other to full feed but declining daylength. After reaching peak production the birds were subjected to a 0, 10 or 20 % reduction in energy intake for the remainder of a 36 week production period. Carcass samples taken at sexual maturity, at peak production and after 24 and 36 weeks of lay indicated that the level of carcass fat did not affect egg production adversely. A 20 % reduction in energy intake reduced production of total and settable eggs significantly during the cold winter months but had no effect on production during the summer months. There was a slight but non-significant improvement in egg production and feed efficiency when energy was restricted by 10 % in the summer. Egg size was not affected significantly by energy restriction in either experiment. Under the conditions of these experiments carcass fat had no significant effect on egg production. Egg production and carcass fat were roughly related to energy intake depending upon the season of the year. POULTRY SCIENCE 54: 200-208, 1975 MOST attempts to restrict the feed or energy intake of laying strain hens while in production have resulted in lower egg production and egg weights (Burmester and Card, 1939; Heywang, 1940). It was tempting to explain the results of these early experi-ments by citing the use of high-fiber, low-en-ergy diets which made it difficult for the hens to overconsume energy. More recent studies in which modern laying diets were employed have yielded results similar to the earlier work. Walter and Aitken (1961) reported a reduction in egg production with White Leg-horns when feed was restricted to 80 % of ad libitum controls. McGinnis and Dronawat (1967) found that restricitng feed intake to 90 % of ad libitum controls reduced egg pro-duction and egg weights in most experiments. Similar results were reported by Polin an