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Effects of genetic polymorphisms at the growth hormone gene on milk yield in Serra da Estrela sheep

Published online by Cambridge University Press:  07 July 2006

Maria do Rosário Marques
Affiliation:
Departamento de Genética e Melhoramento Animal, Estação Zootécnica Nacional, Fonte Boa, 2005-048 Vale de Santarém, Portugal Faculdade de Engenharia de Recursos Naturais, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
Ingrid C Santos
Affiliation:
Departamento de Genética e Melhoramento Animal, Estação Zootécnica Nacional, Fonte Boa, 2005-048 Vale de Santarém, Portugal Faculdade de Engenharia de Recursos Naturais, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
Nuno Carolino
Affiliation:
Departamento de Genética e Melhoramento Animal, Estação Zootécnica Nacional, Fonte Boa, 2005-048 Vale de Santarém, Portugal
Carlos C Belo
Affiliation:
Departamento de Sistemas e Técnicas de Produção Animal, Estação Zootécnica Nacional, Fonte Boa, 2005-048 Vale de Santarém, Portugal
Robert Renaville
Affiliation:
Animal and Microbial Unit, Gembloux Agricultural University, 13 Avenue Maréchal Juin, 5030 Gembloux, Belgium
Alfredo Cravador
Affiliation:
Faculdade de Engenharia de Recursos Naturais, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal

Abstract

The five exons and the 5′ and 3′-untranslated regions (5′-UTR and 3′-UTR) of the oGH gene were screened for mutations using PCR-single strand conformation polymorphism (PCR-SSCP) procedures in 523 Serra da Estrela ewes and were found to be highly polymorphic. The region extending across and between the GH2-N and GH2-Z copies was sequenced allowing the design of primers for the specific PCR amplification of each copy. These were cloned and sequenced in 20 animals representative of all SSCP patterns. The corresponding genotypes were established for each copy following nucleotide sequencing of SSCP alleles. Twenty-four polymorphic sites were found at the GH2-N (or GH1) and fourteen at the GH2-Z copies. Eight amino acid substitutions were predicted at the GH2-N and six at the GH2-Z copies. Milk yield adjusted to 150 lactation days was analysed for the genotype of each oGH gene copy taken separately or together (associated genotypes) by restricted maximum likelihood (REML) through a univariate best linear unbiased prediction (BLUP) animal model with repeated measures. Significant associations between genotypes and milk yield were observed. Within GH2-N genotypes there was a milk yield differential of 21·4±0·2 l/150 d between the most (N7) and the least (N5) productive ones. Within GH2-Z genotypes there was a differential of 21·6±0·2 l/150 d between the most (Z8) and the least (Z1) productive ones. The effect of associated GH2-N and GH2-Z genotypes revealed a differential of 39·6±0·3 l/150 d between the most (N1+Z7) and the least (N3+Z2) productive associated genotypes. The results show that GH2-N and GH2-Z genotypes significantly affect milk yield in Serra da Estrela ewes. Moreover, the apparent joint effect of GH2-N and GH2-Z genotype could improve milk yield in 25% as compared with the mean milk production of the analysed population.

Type
Research Article
Copyright
Proprietors of Journal of Dairy Research 2006

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