Comin A, Cassandro M, Chessa S, Ojala M, Dal Zotto R, De Marchi M, Carnier P, Gallo L, Pagnacco G, Bittante G
Department of Animal Science, University of Padova, Legnaro, Padova, Italy.
J Dairy Sci. 2008 Oct;91(10):4022-7. doi: 10.3168/jds.2007-0546.
The aim of the study was to estimate the effect of the composite CSN2 and CSN3 genotypes on milk coagulation, quality, and yield traits in Italian Holstein cows. A total of 1,042 multiparous Holstein cows reared on 34 commercial dairy herds were sampled once, concurrently with monthly herd milk recording. The data included the following traits: milk coagulation time; curd firmness; pH and titratable acidity; fat, protein, and casein contents; somatic cell score; and daily milk, fat, and protein yields. A single-trait animal model was assumed with fixed effects of herd, days in milk, parity, composite casein genotype of CSN2 and CSN3 (CSN2-CSN3), and random additive genetic effect of an animal. The composite genotype of CSN2-CSN3 showed a strong effect on both milk coagulation traits and milk and protein yields, but not on fat and protein contents and other milk quality traits. For coagulation time, the best CSN2-CSN3 genotypes were those with at least one B allele in both the CSN2 and CSN3 loci. The CSN3 locus was associated more strongly with milk coagulation traits, whereas the CSN2 locus was associated more with milk and protein yields. However, because of the tight linkage between the 2 loci, the composite genotypes, or haplotypes, are more appropriate than the single-locus genotypes if they were considered for use in selection.
本研究的目的是评估复合CSN2和CSN3基因型对意大利荷斯坦奶牛的凝乳、品质和产量性状的影响。在34个商业奶牛场饲养的1042头经产荷斯坦奶牛，与每月的牛群牛奶记录同时进行了一次采样。数据包括以下性状：凝乳时间；凝乳硬度；pH值和可滴定酸度；脂肪、蛋白质和酪蛋白含量；体细胞评分；以及每日牛奶、脂肪和蛋白质产量。采用单性状动物模型，假定有牛群、泌乳天数、胎次、CSN2和CSN3的复合酪蛋白基因型（CSN2-CSN3）的固定效应，以及动物的随机加性遗传效应。CSN2-CSN3的复合基因型对凝乳性状以及牛奶和蛋白质产量均有强烈影响，但对脂肪和蛋白质含量以及其他牛奶品质性状没有影响。对于凝乳时间，最佳的CSN2-CSN3基因型是在CSN2和CSN3位点均至少有一个B等位基因的那些基因型。CSN3位点与凝乳性状的关联更强，而CSN2位点与牛奶和蛋白质产量的关联更强。然而，由于这两个位点之间紧密连锁，如果考虑将其用于选择，复合基因型或单倍型比单一位点基因型更合适。
