Milk proteins, milk protein variants and the importance for the sheep breeding - a review

Milk proteins, milk protein variants and the importance for the sheep breeding - a review Current international knowledge about milk protein polymorphisms in sheep is presented with this report. Importance of sheep milk and known variability of the four caseins alpha(s1)-(CSN1S1), alpha(s2)- (CSN1S2), beta- (CSN2) and kappa- (CSN3) casein and the whey proteins alpha-lact-albumin (LAA) and beta-lactoglobulin (LGB) are described. In the last years a high degree of variability was identified and analysed also using molecular genetic methods for several milk proteins like alpha(s1)- and alpha(s2)-casein, whereas within beta- and kappa-casein as well as alpha-lactalbumin only some polymorphisms are described. Furthermore, first known associations between milk protein polymorphisms, respectively casein haplotypes and milk performance traits and cheese making aptitude, are figured out and discussed for their potential usage in sheep breeding. A future inclusion in sheep breeding programmes requires an increase of milk performance testing, especially in Germany, as a basis for association studies.