Estimation of genetic parameters for litter size after natural and hormone-induced oestrus in sheep

• Published in: Livestock production science Vol. 97; no. 2; pp. 275 - 281
• Main Authors: Baelden, M., Tiphine, L., Poivey, J.P., Bouix, J., Bibé, B., Robert-Granié, C., Bodin, L.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-11-2005; Elsevier
• Subjects: Agricultural sciences; Genetic parameters; Hormone-induced oestrus; Life Sciences; Litter size; Natural oestrus; Sheep; Sheep; Natural oestrus; Litter size; Hormone-induced oestrus; Genetic parameters
• ISSN: 0301-6226; 1872-6070
• DOI: 10.1016/j.livprodsci.2005.05.003

Genetic parameters for litter size after natural and hormone-induced oestrus were estimated for Ovin Ile de France, Blanc du Massif Central and Mouton Vendéen sheep, using REML methods in animal and sire model BLUP for observed litter size and normal scores of litter size. Litters born after hormone-induced oestrus and after natural oestrus were treated as different traits in order to estimate the genetic correlation between the traits and the genetic parameters of each trait. Explanatory variables were the year
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flock
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season of lambing effect, the physiological condition factor combining the type of rearing, age at the first lambing, interval between lambings and number of lambs suckled at the previous lambing, the month of birth nested within gestation number, a permanent environmental effect associated with the ewe and the additive genetic effect (sire or animal effect). For the three breeds, the heritability estimates for natural litter size, equal to 0.10, was higher than the heritability estimates for induced litter size, equal to 0.06. The estimate of genetic correlation between the two fertilization types was closed to 0.75. This result suggests that natural and induced litter size can be considered as two different traits, although controlled by a great number of common genes. This genetic correlation was higher than the previous estimate (0.40) reported by
Bodin (1979) [Bodin, L., 1979. Estimation des paramètres génétiques de la taille de portée des agnelles Lacaune après fécondation sur oestrus naturel et induit. Ann. Génét. Sél. Anim. 11 (4), 413–424].