ASSOCIATIONS BETWEEN CASEIN HAPLOTYPES AND MILK-YIELD TRAITS

The genotyping of 13 sires and 250 of their sons for casein polymorphi sms revealed 10 different haplotypes for Norwegian Cattle. Association s between haplotypes and yields of protein, milk, and fat were studied using a granddaughter design. Three subsets of data containing famili es with haplotypes 1, 5, and 10 were analyzed independently and denote d by analyses 1, 5, and 10, respectively. In addition, all sire famili es of all haplotypes were pooled and analyzed in analysis T. No associ ations were found between haplotypes and traits for milk yield in anal yses 1, 10, and T. However, the null hypothesis of an equal effect wit hin sire of bulls was rejected in analysis 5 for yields of protein and milk. The increase in protein yield associated with haplotype 5 range d from 2.52 to 14.58 kg (from .09 to .51 phenotypic standard deviation s). These results may indicate the presence of at least one quantitati ve trait locus in the region of the casein genes that affects protein yield of Norwegian Cattle. The findings were confirmed with a new anal ysis of two large sire families segregating haplotype 5 (analysis 5N).