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Alpha s1-Casein Testing

Lisa Shepard

ADGA’s Genetic Advancement Committee is charged with developing and promoting policies and procedures that support genetic improvement in dairy goats. Part of our ongoing mission is to provide information regarding current and emerging technologies that will aid breeders and producers in making genetic progress. This is the first in a series of articles designed to provide information about ADGA’s genetic programs to our membership and the industry at large. We welcome your feedback and suggestions. — Elizabeth R. Henning, Chair, Genetic Advancement Committee, American Dairy Goat Association

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 1980s, and is one found in all dairy goat breeds.

These polymorphisms have been found to affect cheesemaking 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 cheesemaking yield observed in milk produced by those animals with strong alleles was 7% higher in comparison with those with medium alleles and 15% 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 cheesemaking yield by selecting for high expression alleles, or selecting for animals with low levels which may be of benefit to those with milk sensitivities. Veterinary Genetics Laboratory located at University of California, Davis, provides such testing in the United States. ADGA members receive a discounted rate of $20.

The test is designed to detect low level variants for casein—E, F, and N. High level variants are then reported as A or B, which represent several specific alleles. A report would appear as follows with animal information: Alpha s1 Casein A/E Interpretation of result code: This test is designed to detect three variants of alpha s1 casein (E, F and N) that are associated with reduced content of this milk protein. Variants, A and B, are associated with a high content of alpha s1 casein in milk. Variants, E, F and N, are associated with a lower content of alpha s1casein in milk.

Any combination of A and B variants will produce high amounts of alpha s1 casein. A combination of A or B variant with E, F or N variant will produce intermediate amounts of alpha s1 casein. Any combination of E, F and N variants will produce low amounts of alpha s1 casein. The animal above, if a doe, would be expected to produce intermediate levels of the casein and pass on either the A or E to their offspring. The animal above, if a buck, would have daughters that would inherit either the A (high level) or E (lower level). The variant inherited from their dam would determine whether they were an intermediate or high level producer of casein.

Link to the following 2009 article, Prevalence of αs1-casein genotypes in American dairy goats at: www.journalofanimalscience.org/content/87/11/3464.long for in-depth information.

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