Milk protein polymorphisms have a significant influence on milk quantity and composition. Kappa-casein is of special interest due to its known relationship with milk quality. In goats, a number of allelic variants have been identified, primarily classified into two groups. Group BIEF alleles (D, E, K, and M) have been shown to have a positive effect on milk yield and technological properties, while group AIEF, the remaining alleles, have a less positive influence on milk composition. The aim of this study was to investigate genetic variation in the kappa-casein genotype of South African goats. PCR-RFLP and DNA sequencing were performed on 68 and 77 samples, respectively. In addition, 84 milk samples were analyzed for milk composition. RFLP analysis revealed that the A and/or B alleles were the most frequent in the populations studied. A frequency of 0.00 was observed for the BIEF variants using DNA sequencing. In all goat types included, the B allele was the most common, with frequencies ranging from 60% in SA Boer goats to 100% in Saanens. The B’ allele had lower frequencies of 0.357 and 0.207 in SA Boer goats and local goat types, respectively. The H allele was present at low frequencies in local goat types (10.3%) and in SA Boer goats (3.6%), but was absent in Saanens. AMOVA results indicated that most of the total variation occurred within populations (80.66%) with the remainder of the variation (FST = 0.1934; p < 0.01) occurring due to genetic differences between populations.
Dissertation (MSc(Agric))--University of Pretoria, 2011.