SummaryUsing SDS-polyacrylamide gel electrophoresis and rocket immunoelectrophoresis, 3 new alleles, designated a,,-Cn'-, α s1 -Cn F and α s1 -Cn o , were identified at the goat a!-Cn locus, in addition to alleles <2,j-Cn!, as!-Cn° and <2,j-Cn! previously reported by B OULANGER et al. (1984). Alleles a,,-Cn', a,,-Cn' and <2,j-Cn! are associated with a high content of a,,-casein (approximate mean contribution of each allele being 3.6 g/I) compared to ( Y ,,-Cn' with a low content (0.6 g/I) and a,,-Cn° with an intermediate content (1.6 g/1) ; a,,-Cn° appears to be a true null allele. In a sample of 213 Alpine females from 49 flocks in West Central France, the frequencies of the 6 alleles were : <2,j-Cn! = 0.14 ; a,,-Cn° = 0.05 ; <2,j-Cn! = 0.01 ; ot,,-Cn' = 0.34 ; a,,-Cn F = 0.41 ; and a, i -Cn° = 0.05. In a sample of 159 Saanen females from 52 flocks of the same region, the frequencies were : <2,j-Cn! = 0.07 ; <2,j-Cn! = 0.06 ; < 2 ,j-Cn<' = 0 ; a 'I -CnB-= 0.41 ; a,,-Cn' ! 0.43 ; <2,j-Cn'" = 0.03. Additional data confirm that loci a, I -Cn and a,,-Cn are closely linked.Preliminary investigations indicated a significant superiority in casein content of milks from goats possessing the allele <2,j-Cn!, as compared to that of milks from goats of genotypes (xs,-Cn F / / <2,j-Cn! and <2,j-Cn! /a 'I -Cn F and, in a large herd (N = 251), a strong correlation was observed between the a,,-casein content and the rennet-casein content of milk (r = 0.68 ; b = 0.64).
