Author
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Proudman, John |
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Submitted to: Turkey Technical Symposium Proceedings
Publication Type: Proceedings Publication Acceptance Date: 10/20/1997 Publication Date: N/A Citation: N/A Interpretive Summary: Broodiness, or incubation behavior, is a major cause of poor egg production in turkey breeder hens. Retained from its non-domesticated ancestors, broodiness is the hen's natural tendency to cease laying and incubate a clutch of eggs. While genetic selection for egg production has largely eliminated broodiness from egg-type chickens, and greatly reduced this trait in broiler-breeder hens, broodiness remains a substantial problem in commercial turkey breeder flocks. Industry estimates suggest that elimination of broodiness would save the industry between $60 and $100 million per year. Basic research has identified many of the key physiological events that lead to broodiness. This review discusses the environmental factors that initiate incubation behavior, the neural and endocrine stimuli that are required for broodiness to occur, and the physiological changes that must occur in the hen to result in persistent nesting, regression of the ovary, and lost egg production. The effectiveness of management practices used to prevent or disrupt broodiness is discussed, and the development of new biological strategies for preventing broodiness is described in the context of the physiology and genetics of the turkey hen. Technical Abstract: Broodiness or incubation behavior is a major cause of poor egg production in turkey breeder hens. Retained from its non-domesticated ancestors, broodiness is the hen's natural tendency to cease laying and incubate a clutch of eggs. While genetic selection for egg production has largely eliminated broodiness from egg-type chickens, and greatly reduced this trait in broiler-breeder hens, broodiness remains a substantial problem in commercial turkey breeder flocks. A study conducted under commercial conditions indicated that more than 1% of hens were identified daily as broody, and that more than 50% of farm labor costs were spent on prevention or disruption of broodiness. Environment and behavior are known to markedly affect the incidence and duration of broodiness. This review describes how environmental factors are thought to initiate physiological changes in some hens that lead to broodiness. The role of prolactin in broodiness is described, and the cellular changes that occur in lactotroph and somatotroph populations as the hen changes from laying to incubating is shown to support increased prolactin secretion. A discussion of the regulation of prolactin secretion by vasoactive intestinal peptide provides an understanding of the physiological basis for new vaccination strategies designed to prevent the initiation of broodiness. Possible new genetic- based strategies for reducing incubation behavior in turkey breeder flocks are also discussed. |
