Genetic variation at the ?S1-casein locus (CSN1S1) is recognized as being crucial in the selection of dairy goats for cheese yield. At this locus, the existence of alleles that have strong, intermediate, weak, and null favorable effects on cheese yield and curd firmness is well known. Selection for alleles that have a strong favorable effect has been deliberately carried out, espe- cially in France. In fact, the importance of ?S1-casein in selection was recently confirmed in the selling policies of semen, where bucks are marketed according to their genotypes. We evaluated genotypes and alleles frequen- cies at the ?S1-casein locus in 491 Italian Saanen and Alpine goats and compared them with previous data to investigate their evolution over the past decade. We also estimated soft cheese yield in a subset of the most represented genotypes to quantify the economic im- portance of considering the genetic trend of ?S1-casein genotype frequencies. We found a significant increase in frequency of the allele with the strongest favorable ef- fect, A (+12 and +13%), and of the intermediate allele E (+17 and +7%) in Saanen and Alpine goats, respec- tively. Surprisingly, the frequency of the strong allele B decreased strikingly over time (-12% in Saanen, -6% in Alpine from 2004 to 2012). This is consistent with the current marketing of semen, in that bucks that are homozygous for strong (AA and BB) and intermediate alleles (EE) and even heterozygous for these alleles (BE and AE) are considered equal. It is worth noting that this practice strongly penalizes the best breeders that have flocks composed almost entirely of goats that are homozygous for strong alleles. For heterozygous goats, we estimated an economic loss of EUR85 and EUR215 per goat per lactation, respectively, for AE and BE, compare with AA and BB genotypes. The marketing of buck se- men should clearly differentiate these 2 alleles to ensure the best economic genetic progress at this locus.
Short communication: The unusual genetic trend of ?S1-casein in Alpine and Saanen breeds
S Chessa;
2014
Abstract
Genetic variation at the ?S1-casein locus (CSN1S1) is recognized as being crucial in the selection of dairy goats for cheese yield. At this locus, the existence of alleles that have strong, intermediate, weak, and null favorable effects on cheese yield and curd firmness is well known. Selection for alleles that have a strong favorable effect has been deliberately carried out, espe- cially in France. In fact, the importance of ?S1-casein in selection was recently confirmed in the selling policies of semen, where bucks are marketed according to their genotypes. We evaluated genotypes and alleles frequen- cies at the ?S1-casein locus in 491 Italian Saanen and Alpine goats and compared them with previous data to investigate their evolution over the past decade. We also estimated soft cheese yield in a subset of the most represented genotypes to quantify the economic im- portance of considering the genetic trend of ?S1-casein genotype frequencies. We found a significant increase in frequency of the allele with the strongest favorable ef- fect, A (+12 and +13%), and of the intermediate allele E (+17 and +7%) in Saanen and Alpine goats, respec- tively. Surprisingly, the frequency of the strong allele B decreased strikingly over time (-12% in Saanen, -6% in Alpine from 2004 to 2012). This is consistent with the current marketing of semen, in that bucks that are homozygous for strong (AA and BB) and intermediate alleles (EE) and even heterozygous for these alleles (BE and AE) are considered equal. It is worth noting that this practice strongly penalizes the best breeders that have flocks composed almost entirely of goats that are homozygous for strong alleles. For heterozygous goats, we estimated an economic loss of EUR85 and EUR215 per goat per lactation, respectively, for AE and BE, compare with AA and BB genotypes. The marketing of buck se- men should clearly differentiate these 2 alleles to ensure the best economic genetic progress at this locus.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
