Composite trait selection to improve reproduction and ewe productivity: a review

Abstract

Abstract. Reproduction and ewe productivity are complex composite traits that are influenced by several component traits. Genetic improvement by selection for an individual component trait may not always be advantageous because adverse or neutral genetic relationships can exist among the component traits. Selection for an overall composite trait of ewe productivity, defined as litter weight weaned per ewe joined, can result in a balanced biological composite trait with favourable responses in component traits including fertility, number of lambs born, lamb survival, lactation and lamb growth. Selection for litter weight weaned may also overcome adverse genetic relationships among reproductive component traits. This review examines the genetic responses of selecting directly for litter weight weaned, compared with selection responses for one or more of its component traits. It is concluded that selection to improve reproductive efficiency and ewe productivity, 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.

Characterization of the productive performance of Highlander sheep in Southern Chile. I. Female reproductive traits

“…Sustainable sheep production systems are based on valuable lamb sold per ewe exposed to rams under balanced cost of production (Lupton, 2008;Snowder and Foggarty, 2009;Fogarty, 2009). Under this context prolificacy and survival of twin lambs have the most critical impact in sheep productivity (Young et al, 2014).…”

Genetic parameters for ewe reproduction with objectively measured wool traits in Elsenburg Merino flock

“…Earlier investigations (Dickerson, 1970) have stressed the importance of reproduction and mothering ability of ewes, and growth and survival of lambs for efficient lamb production to satisfy the demand for quality wool and meat by consumers. Research has suggested the possibility of improving ewe reproduction genetically through direct and indirect selection because of its composite nature (Olivier et al, 2001;Cloete, 2002;Snowder & Fogarty, 2009). However, it was contended that selection for a component of a composite trait does not always result in an overall improvement of a complex trait such as ewe reproduction (Snowder & Fogarty, 2009).…”

“…Research has suggested the possibility of improving ewe reproduction genetically through direct and indirect selection because of its composite nature (Olivier et al, 2001;Cloete, 2002;Snowder & Fogarty, 2009). However, it was contended that selection for a component of a composite trait does not always result in an overall improvement of a complex trait such as ewe reproduction (Snowder & Fogarty, 2009).…”

Genetic analysis of longevity and lamb survival from birth to yearling in Moghani sheep

“…But genetic progress is not exclusively depending on the estimate of heritability for a specific, and also reliant on generation interval, intensity of selection, and the genetic variance for a trait (Brien et al 2010). Genetic progress for survival trait in sheep would be improved by possible methods, including the implementation of indirect selection through direct selection for more heritable trait which have high genetic correlation with survival traits, progeny testing of sires, selection on the basis of the total weaning weight of lambs and application of other relatives information in genetic evaluations (Snowder and Fogarty 2009;Brien et al 2010). In addition, Hatcher et al (2010) suggested that genetic gains would be possible for lamb survival through using repeated measurements.…”