Reproductive failure in overweight male and female broiler breeders

Abstract

The strong negative relationship between body weight and reproductive efficiency in broiler parent stocks has necessitated the management practice of feed restriction. There is relatively little known about how feed restriction impacts on reproduction in terms of gonadal form and function. This paper is a review of four experiments conducted with female and male commercial broiler breeders to further define the consequences of excessive feed allocation. In one study, hens were full-fed or feed restricted to typical industry target weights during the period from 22 to 62 weeks of age. It was observed that ad libitum feeding resulted in an increase in body weight of approximately 700 g and a reduction in egg production of 40 eggs. A further study was carried out as a 2 × 2 factorial design of full feeding vs. feed restriction during rearing and lay. The greater the duration of ad libitum feeding, the lower was the rate of egg production and the higher the incidence of multiple-yolked eggs, erratic lay and shell quality problems. Fertility and hatchability were significantly reduced with full feeding. Full-fed hens had an increased number of large ovarian follicles, and it is thought that the existence of partial or complete double or in some cases triple hierarchies resulted in an impairment of the normal control of the ovulatory cycle. In a third study, it was observed that the number of large follicles increased from 5.3 to 7.0 follicles in response to 14 days of ad libitum feeding. It is obvious that the loss of regulation of the ovarian hierarchy associated with over feeding can occur in a short period of time. The consequences of the ad libitum feeding of caged male broiler breeders during the period from 22 to 30 weeks of age was studied. The full-fed males gained almost 1 kg of body weight during the first week of full feeding. Dissection of some carcasses at 30 weeks of age revealed that breast muscle weight and fat pad weight were significantly greater in full-fed birds than in feed-restricted birds. The number of males in semen production early in the adult period (26 to 30 weeks of age) was numerically higher for the full-fed birds. The converse was true at the later stages of semen production. The benefits of controlling body weight in males early in the breeding period are evident much later at the end of the breeding period.