The occurrence of the
Leu127/Val127
variants of the bovine growth hormone (bGH) gene and their effect on milk
production traits was investigated in Australian Holstein-Friesian cattle.
Animals were genotyped for the
Leu127/Val127
variants, with RFLP methodology, using PCR and AluI
digestion of PCR products (AluI-RFLP). Alleles
Leu127 and
Val127 occurred with frequencies
of 82% and 18%, respectively. The quantitative effect of this
polymorphic site on milk-production traits was estimated from lactation data
and test-day data. Results from the 2 data sets consistently showed that the
Leu127 allele is associated with
higher production of milk, fat, and protein and is dominant to
Val127. The average effects of
the gene substitution are 95 L for milk yield, 7 kg for fat yield, and 3 kg
for protein yield per lactation. This locus may be directly responsible for
quantitative variation or it may be a marker for a closely linked quantitative
trait locus (QTL) for milk-production traits in Australian dairy cattle. In
either case, it will be useful as an aid to selection for improvement of milk
production traits. As the Leu127
allele is dominant, selection of AI sires homozygous for the
Leu127 allele
(Leu127/Leu127) will result in maximum benefit without the need for genotyping cows.
Sequence Variations in the Bovine Growth Hormone Gene Characterized by Single-Strand Conformation Polymorphism (SSCP) Analysis and Their Association with Milk Production Traits in Holsteins
