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首页> 外文期刊>Tropical Animal Health and Production >Estimation of genetic and phenotypic relationships between age at first calving and productive performance in Iranian Holsteins
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Estimation of genetic and phenotypic relationships between age at first calving and productive performance in Iranian Holsteins

机译：伊朗产犊牛的初产犊年龄与生产性能之间的遗传和表型关系估计

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摘要

Calving records from the Animal Breeding Center of Iran collected from January 1990 to December 2007 and comprising 207,106 first calving events of Holsteins from 2,506 herds were analysed using univariate and bivariate linear sire models to estimate heritabilities and genetic correlations between age at first calving (AFC) and productive performance. Average AFC was 26.48 months in this study. The peak in the frequency distribution of AFC clearly exists coinciding with cows calving for the first time at approximately 25 months of age. Heritability estimate for AFC was 0.34 which was greater than the corresponding values for productive traits. The heritability estimates were low to medium for productive traits which ranged from 0.17 to 0.26 for cows in their first calvings. Except for fat and protein percentages of milk, phenotypic and genetic correlations between AFC and productive performance traits were low to moderately negative. Range of genetic correlations between productive traits was -0.53 to 0.99. Reduction of age at first calving appeared to have a negative effect on first lactation protein and fat percentages; however, it had positive effects on milk yield, fat yield, protein yield and their mature equivalents. It seems that reducing age at first calving to 24-25 months is probably more profitable than reducing age at first calving to an earlier time in Iranian conditions.
机译：使用单变量和双变量线性父亲模型分析了1990年1月至2007年12月从伊朗动物育种中心收集的犊牛记录，包括来自2,506个牛群的207,106头荷斯坦牛的第一次犊牛事件，以评估首次犊牛（AFC）的遗传力和遗传相关和生产性能。在这项研究中，平均AFC为26.48个月。显然，AFC频率分布的峰值与大约25个月大的母牛第一次产犊相吻合。 AFC的遗传力估计值为0.34，大于生产性状的相应值。对生产性状的遗传力估计值从低到中，在初产犊牛的遗传特性范围从0.17到0.26。除了牛奶中的脂肪和蛋白质百分比外，AFC与生产性能特征之间的表型和遗传相关性均低至中度为负。生产性状间遗传相关性的范围是-0.53至0.99。第一次产犊时年龄的减少似乎对第一次泌乳蛋白和脂肪百分比有负面影响;然而，它对牛奶产量，脂肪产量，蛋白质产量及其成熟等价物具有积极影响。在伊朗的情况下，将初产犊年龄降低到24-25个月似乎比在初产犊阶段降低年龄更有利。

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