Author
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Snowder, Gary |
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Submitted to: Archivos Latinoamericanos De Produccion Animal
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/8/2007 Publication Date: 9/10/2008 Citation: Snowder, G.D. 2008. Genetic improvement of overall reproductive success in sheep: A review. Archivos Latinoamericanos De Produccion Animal. 16(1):32-40. Interpretive Summary: Reproduction is a complex composite trait influenced by many components including puberty, ovulation, estrus, fertilization, embryo implantation, pregnancy, parturition, lactation, and mothering ability. The genetic effect on each component of reproduction varies. Genetic improvement of composite traits can occur by selection for individual components traits, some combination of individual component traits, or by direct selection for the composite trait. This review discusses the responses of selecting directly for litter weight weaned compared to selection responses for one of its component traits. Litter weight weaned is defined as the composite trait of reproductive efficiency in sheep. Litter weight weaned is a biological selection index determined by environmental factors under which it is selected for. Selection for litter weight weaned results in a balanced biological composite trait with favorable responses in its component traits as reported in the literature. Selection to improve reproductive efficiency under most production and environmental systems would benefit from selection for a composite trait such as litter weight weaned rather than for a single component trait. Technical Abstract: Reproduction is an economically important complex composite trait in sheep. Genetic improvement of composite traits can occur by selection for individual components traits, some combination of individual component traits, or by direct selection for the composite trait. This review discusses the responses of selecting directly for litter weight weaned compared to selection responses for one of its component traits. Litter weight weaned is concluded to be a biological selection index determined by environmental factors under which it is selected for. Selection for litter weight weaned can result in a balanced biological composite trait with favorable responses in component traits such as fertility, number of lambs born, lamb survival, lactation, and lamb growth. It is concluded that selection to improve reproductive efficiency under most production and environmental systems would benefit from selection for a composite trait such as litter weight weaned rather than for a single component trait. |
