Distribution of ovine alphas1-casein D variant in Sarda breed
1997
Papoff, C.M. | Battacone, G. | Pinna, R.I. (Universita degli Studi di Sassari (Italy)) | Fraghi, A. | Piredda, G. | Pirisi, A. | Mauriello, R. | Chianese, L.
Sarda sheep is the most important dairy breed of the Mediterranean area and its milk is entirely processed into cheese. Five alphas1-casein electrophoretic variants - A, B, C, D and E - were recently shown and the primary structure was determined for A, C and D. The D allele is related to a lower total casein content; moreover the milk produced by ewes with this allele has poor rennet-clotting properties and a lower cheese yield than the milk with the C allele. Individual milk samples from 2700 yearlings were collected from 150 flocks of the Sarda recorded population. A further 652 individual milk samples were collected from 78 flocks of the unrecorded population and chosen from yearlings, 3-year-old and 5-year-old ewes (33 per cent of the samples from each age group). Whole milk, diluted with 9 M urea and 4 per cent 2-mercaptoethanol with the addition of 75 per cent glycerol, was placed in the electrophoresis gel. Alkaline Disc-PAGE was performed on a Mini Gel System. The frequency of the D allele in the recorded flocks was 0.027, very close to that of the unrecorded population (0.028), where the D allele frequency in yearlings, 3-year-old and 5-year-old ewes was, respectively, 0.028, 0.028 and 0.023. These comparisons showed that the frequency of allele D was: (i) the same for the two populations of ewes; (ii) uniform in time. The detected frequency of the D allele of alphas1-casein in Sarda sheep is actually close to the value 0.02, already detected for other breeds. Our work reveals the strong importance of flock-factor in the distribution of the genetic variants of caseins in traditional sheep breeding. The Disc-PAGE method was found to be suitable for the determination of the frequency of alphas1-casein D allele. This method is simple to realize, has low analysis costs, and a fast determination time.
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