Abstract

Cow milk might be associated to gastrointestinal disorders and abdominal pain in some people, which are, in part, due to the digestion of A1 beta-casein. Within this context, A2 milk has emerged as an alternative since it only contains A2 beta-casein that does not cause these complications. This milk is produced by cows with the A2A2 genotype. The aim of this study was to investigate the allele and genotype frequencies for the beta-casein gene in Guzerat cattle and to evaluate the feasibility of selection and production of A2 milk. The genotypes of 283 Guzerat cows from 10 herds were analyzed. The frequency of the A2A2 genotype was 0.80 and the frequency of the A2 allele was 0.90. These frequencies are slightly lower than those reported in previous studies involving populations of the same breed, but the number of animals, herein, genotyped was higher. Thus, the estimates are believed to be better and are also equally high. The Guzerat cattle has the potential for A2 milk production since most animals of the herd carry the favorable genotype for A2 milk production. Furthermore, the frequency of the A2A2 genotype can be rapidly increased by marker-assisted selection without compromising genetic variability.

摘要

牛奶可能与某些人的胃肠道疾病和腹痛有关，这在一定程度上是由于 A1 β-酪蛋白的消化。在这种情况下，A2 牛奶作为替代品应运而生，因为它只含有不会引起这些并发症的 A2 β-酪蛋白。这种牛奶由具有 A2A2 基因型的奶牛生产。本研究的目的是调查 Guzerat 牛 β-酪蛋白基因的等位基因和基因型频率，并评估选择和生产 A2 牛奶的可行性。分析了来自 10 个牛群的 283 头 Guzerat 奶牛的基因型。A2A2 基因型的频率为 0.80，A2 等位基因的频率为 0.90。这些频率略低于先前涉及同一品种种群的研究中报告的频率，但这里的动物数量，基因分型更高。因此，估计值被认为更好并且同样高。Guzerat 牛具有生产 A2 牛奶的潜力，因为牛群中的大多数动物都携带有利于 A2 牛奶生产的基因型。此外，A2A2 基因型的频率可以通过标记辅助选择快速增加，而不会影响遗传变异性。