The alpha s1-casein is a protein polymorphism of goat milk first described in Europe, in the French Alpine and Saanen breeds, in the early nineteen eighties, and is one found in all dairy goat breeds.

These polymorphisms have been found to affect cheese-making due to differences in protein content, renneting properties (faster coagulation and firmer curd) and a possible connection in relation to cheese flavor. In one study, the results of researches conducted on homozygous individuals for the various alleles confirmed the effects of genotype on the casein content in milk by showing the cheese-making yield observed in milk produced by those animals with strong alleles was 7 per cent higher in comparison with those with medium alleles and 15 per cent  higher than those with weak alleles.

Knowing the specific genetic polymorphism at goat casein loci on breeding stock would allow the breeder to set up breeding and selection programs targeted towards the improvement of cheese-making yield by selecting for high expression alleles, or selecting for animals with low levels which may be of benefit to those with milk or casein  sensitivities.

Fortunately, Veterinary Genetics Laboratory at University of California, Davis, is making such testing possible in the United States. The test is designed to detect animal with high level variants and low level variants for casein. Accordingly, any combination of animal with high content of alpha s1-casein will produce high amounts of alpha s1-casein in milk. A combination of animal with a high content of alpha s1-casein in milk and low content of alpha s1-casein will produce intermediate amounts of alpha s1-casein. Any combination of animal with low content of alpha s1-casein will produce low amounts of alpha s1-casein in milk.

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