CORRELATION OF THE ALPHA-LACTALBUMIN (-PRODUCTION AND MILK-COMPOSITION OF HOLSTEINS(15) POLYMORPHISM TO MILK)

The alpha-lactalbumin (+15) polymorphism (a single base variation 15 b asepairs 3' of the alpha-lactalbumin transcription start point) was ex amined for its usefulness as a genetic marker for Holsteins. The +15 p olymorphism is located in a region of the gene that is potentially inv olved in the regulation of alpha-lactalbumin gene expression. Animals from two dairy herds and young sires from progeny-testing programs of four Al organizations were used in the analysis. A group of sons from a heterozygous sire were also evaluated. Each individual animal was ge notyped at the alpha-lactalbumin (+15) locus, and differences of genot ypes were investigated. Estimated differences among alleles were calcu lated for PTA for milk, kilograms of protein, protein percentage, prot ein dollars, kilograms of fat, fat percentage, and fat dollars. Animal s having the alpha-lactalbumin (+15) AA (an adenine on both alleles at position +15) genotype had statistically higher PTA for milk, kilogra ms of protein, protein dollars, kilograms of fat, and fat dollars than did the alpha-lactalbumin (+15) BB (a cytosine, guanine, or thymine o n both alleles at position +15) animals. The alpha-lactalbumin (+ 15) BB animals had higher protein and fat percentages than the alpha-lacta lbumin (+ 15) AA animals. Animals that were heterozygous at this locus , alpha-lactalbumin (+15) AB, had intermediate values for all traits a nalyzed. These results indicate a potential marker or actual locus eff ect of the alpha-lactalbumin (+15) polymorphism in Holstein cattle.