Frattini S, Nicoloso L, Coizet B, Chessa S, Rapetti L, Pagnacco G, Crepaldi P
Dipartimento di Scienze Veterinarie e Sanità Pubblica, Università degli Studi di Milano, 20122 Milan, Italy.
Istituto di Biologia e Biotecnologia Agraria, Consiglio Nazionale delle Ricerche UOS di Lodi, 26900 Lodi, Italy.
J Dairy Sci. 2014 Dec;97(12):7975-9. doi: 10.3168/jds.2014-7780. Epub 2014 Oct 11.
Genetic variation at the αS1-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, especially in France. In fact, the importance of αS1-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 frequencies at the αS1-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 importance of considering the genetic trend of αS1-casein genotype frequencies. We found a significant increase in frequency of the allele with the strongest favorable effect, A (+12 and +13%), and of the intermediate allele E (+17 and +7%) in Saanen and Alpine goats, respectively. 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 €85 and €215 per goat per lactation, respectively, for AE and BE, compare with AA and BB genotypes. The marketing of buck semen should clearly differentiate these 2 alleles to ensure the best economic genetic progress at this locus.
αS1-酪蛋白基因座（CSN1S1）的遗传变异被认为在奶山羊奶酪产量的选育中至关重要。在这个基因座上，存在对奶酪产量和凝乳硬度有强、中、弱和无有利影响的等位基因，这是众所周知的。特别是在法国，人们特意选择具有强有利影响的等位基因。事实上，αS1-酪蛋白在选育中的重要性最近在精液销售政策中得到了证实，在精液销售中，公羊是根据其基因型进行销售的。我们评估了491只意大利萨能山羊和阿尔卑斯山羊αS1-酪蛋白基因座的基因型和等位基因频率，并将它们与之前的数据进行比较，以研究它们在过去十年中的演变。我们还估计了最具代表性的基因型子集中软奶酪的产量，以量化考虑αS1-酪蛋白基因型频率的遗传趋势的经济重要性。我们发现，在萨能山羊和阿尔卑斯山羊中，具有最强有利影响的等位基因A（分别增加了12%和13%）和中等等位基因E（分别增加了17%和7%）的频率显著增加。令人惊讶的是，强等位基因B的频率随时间显著下降（从2004年到2012年，萨能山羊中下降了12%，阿尔卑斯山羊中下降了6%）。这与当前的精液销售情况一致，因为纯合强等位基因（AA和BB）和中等等位基因（EE）甚至这些等位基因的杂合子（BE和AE）的公羊被视为相同。值得注意的是，这种做法严重惩罚了那些几乎完全由纯合强等位基因山羊组成羊群的最佳育种者。对于杂合山羊，与AA和BB基因型相比，我们估计AE和BE基因型的山羊每产奶期每只山羊分别损失85欧元和215欧元。公羊精液的销售应明确区分这两个等位基因，以确保在该基因座上实现最佳的经济遗传进展。
