Institute of Animal Breeding and Genetics, University of Giessen, Giessen, Germany.
J Anim Sci. 2020 Oct 1;98(10). doi: 10.1093/jas/skaa280.
The objectives of this study were to investigate milk casein polymorphisms in dams and to determine the impacts of maternal casein genotypes on growth traits of their sucking calves. Milk samples from 433 dams of the breeds German Angus (GA) and German Simmental (GS) were typed at the milk protein loci α s1-casein (αs1-CN), β-casein (β-CN), α s2-casein (αs2-CN), and κ-casein (κ-CN) via isoelectric focusing. Associations between casein genotypes in maternal milk with growth traits of their 1,872 calves were analyzed until the age of weaning using linear mixed models, considering either genotypes of individual casein loci (model 1) or composite α s1-β-α s2-κ-CN genotypes within the casein cluster (model 2). Besides environmental effects such as sex, age of the dam, and calving year-season, genetic effects (breed group and maternal and paternal effects) were considered in statistical models. The composite casein genotype BBǀA2A2ǀAAǀAB (order of genes on bovine chromosome 6: α s1-ǀβ-ǀα s2-ǀκ-CN) was associated with greater average daily weight gains (ADG) and heavier age-adjusted weaning weights (WW) of calves (P < 0.05). The effects of composite genotypes on birth weight of calves were similar (P > 0.05; model 2). With regard to individual casein loci, greater ADG and WW were observed for calves from dams with the genotypes κ-CN BB and α s1-CN BB, respectively (P < 0.05; model 1). Age-adjusted WW was largest for calves from dams carrying the κ-CN genotype BB (215 kg) compared with calves representing the maternal AB and AA genotypes (both 204 kg). Results from the present study suggested selectable casein genotypes due to their nutritional value of milk (value in terms of offspring performances), offering new perspectives for breeding strategies in beef cattle to improve preweaning calf performance.
本研究旨在研究母奶牛乳蛋白多态性，并确定母体酪蛋白基因型对其哺乳期小牛生长性状的影响。通过等电聚焦，对来自德国安格斯牛（GA）和德国西门塔尔牛（GS）的 433 头奶牛的乳样进行了乳蛋白座αs1-酪蛋白（αs1-CN）、β-酪蛋白（β-CN）、αs2-酪蛋白（αs2-CN）和κ-酪蛋白（κ-CN）的基因分型。采用线性混合模型分析了母奶中酪蛋白基因型与 1872 头小牛生长性状的关联，直到断奶年龄，同时考虑了单个酪蛋白座基因型（模型 1）或酪蛋白簇内的复合αs1-β-αs2-κ-CN 基因型（模型 2）。除了环境因素（如性别、母畜年龄和产犊季节）外，统计模型还考虑了遗传因素（品种组和母本和父本效应）。复合酪蛋白基因型 BBǀA2A2ǀAAǀAB（牛染色体 6 上基因的顺序：αs1-ǀβ-ǀαs2-ǀκ-CN）与小牛的平均日增重（ADG）和断奶体重（WW）的增加有关（P < 0.05）。复合基因型对小牛出生体重的影响相似（P > 0.05；模型 2）。对于单个酪蛋白座，母奶中κ-CN BB 和 αs1-CN BB 基因型的小牛具有更大的 ADG 和 WW（P < 0.05；模型 1）。与携带κ-CN 基因型 AB 和 AA 的小牛相比，携带κ-CN 基因型 BB 的母畜的断奶体重最大（215 kg）。本研究结果表明，由于牛奶的营养价值（就后代表现而言），可选择酪蛋白基因型，为提高育肥牛的哺乳期前小牛性能的育种策略提供了新的视角。
