کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
2440304 1108115 2007 5 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Short Communication: Changes in the Association Between Milk Yield and Age at First Calving in Holstein Cows with Herd Environment Level for Milk Yield
موضوعات مرتبط
علوم زیستی و بیوفناوری علوم کشاورزی و بیولوژیک علوم دامی و جانورشناسی
پیش نمایش صفحه اول مقاله
Short Communication: Changes in the Association Between Milk Yield and Age at First Calving in Holstein Cows with Herd Environment Level for Milk Yield
چکیده انگلیسی

The aim of this study was to evaluate the effect of herd environment class on the genetic and phenotypic relationships of mature equivalent milk yield (MY) on age at first calving (AFC). Data analyzed were 248,230 first parity records of Holstein cows, daughters of 588 sires in 3,042 herds in the United States. Heritability for AFC was 0.33 ± 0.01 and 0.20 ± 0.01 in high and low environment herds, respectively, and 0.47 ± 0.01 in the complete data set. The correlation between AFC sires’ predicted breeding values of low and high classes was 0.69. Genetic correlations between MY and AFC were −0.52 ± 0.02 and −0.31 ± 0.03 in high and low environment herds, respectively, and −0.44 ± 0.02 in the complete data set representing intermediate environments. If selection is based on the whole data set, expected correlated responses for AFC estimated as a result of 1,000 kg of genetic gain in MY, for high and low herd environment herds were −26.1 and −15.3 d, respectively, and −32.6 for the complete data set; hence the highest reduction in AFC occurs in intermediate environment herds. Different estimates of the heritability of AFC, the correlation between AFC breeding values of low and high classes as well as changes in the genetic correlation between MY and AFC across environments indicate genotype × environment interaction. Caution in interpretation is warranted because genetic relationships are dynamic, especially in populations undergoing selection. Current relationships may differ from those during the time period of the present study (1987–1994). Notwithstanding this possibility, methods and findings from the present study provide insight about the complexity of genetic association and genotype × environment interactions between AFC and MY.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Dairy Science - Volume 90, Issue 10, October 2007, Pages 4830–4834
نویسندگان
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