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Verification of the Occurrence of the _s1-Casein A Allele in Red Danish Cattle¹

Eastern Utilization Research and Development Division, ARS, USDA, Philadelphia, Pennsylvania 19118

B. Larsen

and Department of Physiology, Endocrinology and Bloodgrouping, The Royal Veterinary and Agricultural College, Copenhagen V., Denmark

ABSTRACT

_s1-Casein A, a rare genetic polymorph of the _s1-casein fraction of cow's milk, probably arose through the sequential deletion of eight amino acid residues. The _s1-A allele was thought to occur only in American Holstein cattle; however, it has been reported to occur in low frequency in Red Danish cattle. No ancestral relationship can be found between Red Danish cattle and the Holstein breed, hence further confirmation of the identity of these two polymorphs was sought. The proteins were isolated by DEAE-cellulose chromatography and the fingerprints of their chynotryptic digests compared. The _s1-A variant from the Red Danish breed proved to be identical with that of the Holstein breed where _s1-A was first observed. Therefore, it is proposed that this mutant form of _s1-casein is of more ancient ancestry, since no relationship between the Red Danish and the American Holstein breeds can be documented.

¹ Rødt Dansk Malkevaeg.