Genetic variants of alphas1-CN in goat milk:: breed distribution and associations with milk composition and coagulation properties

One dairy goat herd of mixed breeds was investigated for frequency of genetic variants of alpha(s1)-casein (alpha(s1)-CN) and relationships between the genetic variants, milk composition, coagulation properties, and breed. Milk composition (percent total solids, solids-non-fats (SNF), fat, protein, casein, and alpha(s1)-CN), genetic variants of alpha(s1)-CN, and coagulation properties (coagulation time, coagulation rate, and curd firmness) were determined for the milk of 93 individual goats. The elution order of the alpha(s1)-CN genetic variants by reverse-phase high pressure liquid chromatography was D, F, (E and B3), C, A, B2 or B1. The frequencies of individual variants, in descending order, were F (52.7%), E (18.38), A (9.7%), B1 or B2 (4.8%), O and D (4.8% each), C (2.7%), and B3 (2.2%). The most common allele combinations were F/F (37.6%), FIE (10.8%), and E/E (10.8%). Milks containing at least one 'high type' genetic variant Ic(,l-CN A, B1, B2, B3, or C) contained higher percent total solids, SNF, protein, and alpha(s1)-CN than milks that contained only 'low type' variants (alpha(s1)-CN F or D) or were homozygous for the null variant (alpha(s1)-CN O/O). Alpha(s1)-CN genetic variants were not highly correlated with coagulation properties. Milk from Nubians was more likely to contain a high type genetic variant than Alpine milk. (C) 2000 Elsevier Science B.V. All rights reserved.