Growth hormone influences milk yield, possibly through the control of mammogenesis and/or lactogenesis. Ovine GH gene (oGH) is duplicated, presenting GH2-N (or GH1) and GH2-Z copies expressed in the pituitary and in the placenta, respectively. Polymorphisms at the oGH gene were previously detected in ovine. The objectives of this study were to identified oGH2-N protein variants in "Serra da Estrela" sheep and to study their influence upon ewe's milk yield. oGH2-N gene haplotypes characterisation disclosed ten possible oGH2-N protein variants differing between them in up to four residues. Heterozygous ewes presenting oGH2-N phenotype AB produced more 22.60.5 L/150 d of milk than homozygous AA ewes, which represents +15% of milk yield in 150 lactation days. Though variant B is rare in the population, it contains a possible tool for improving milk yield in "Serra da Estrela" ewes.

M. R Marques, I. C Santos, N. Carolino, C. C Belo, A. Cravador

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume , , 02.09, 2006
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