Document Type : Original Article
Authors
1
Animal Production Department, Faculty of Agriculture, Kafrelsheikh University
2
department of animal production, fac. of agric., kafrelsheikh univ.
3
Animal Production Research Institute (ARRI), Agricultural Research Center (ARC), Dokki, Egypt
4
Department Animal production / Faculty of Agriculture / kafr El-Sheikh University
5
Department of Animal, Poultry and Fish Production, Faculty of Agriculture, Damietta University, Egypt
Abstract
This study aims to maximize genetic gain by inclusion some productive and reproductive traits in the selection indices. The study utilized data from 1245 first lactation Friesian cow records. The data were related to 305-day milk yield (305dMY, kg), total milk yield in each lactation (TMY, kg), lactation period (LP, d), calving interval (CI, d), days open (DO, d), and number of services per conception (NSC, service) at Sakha and El-Karada farms in Kafr El Sheikh governorate, through 1998 to 2015. Statistical analysis used animal model that included month and year of calving, farm, and age at first calving as fixed factors and animal and residuals as random effects. The month of calving and age at first calving showed non-significant effects on studied traits. The means of 305dMY kg, TMY kg, LP d, CI d, DO d, and NSC count were 3092, 3283, 287, 371, 83, and 1.8, respectively. The heritability estimates (h2) for 305dMY kg, TMY kg, LP d, CI d, DO d, and NSC count were 0.36, 0.41, 0.20, 0.19, 0.18, and 0.21. Estimates of h2 indicated that improvement of genetic merit could be achieved through a selective breeding program with better management practices. Genetic correlations (rg) among the studied traits were positive and high ranging from 0.74 to 0.92. Similar trend was observed in phenotypic correlations which varied between 0.18 and 0.86. The present results suggested that it is important to include productive and fertility traits in selection indices for Friesian cows under Egyptian conditions in order to achieve higher genetic merit.
Heritability estimates (h2) for the previous traits were 0.36, 0.41, 0.20, 0.19, 0.18, and 0.21, successively. Estimates of h2 declared that improvement of genetic merit could be achieved through a selective breeding program with better management practices. The genetic correlations (rg) between above studied traits were positive and high and varied between 0.74 - 0.92. The same direction was obtained in phenotypic correlations, but it was lower than and varied between 0.18 - 0.86. The current results suggested that the importance of including productive and fertility traits when selection is exercised in Friesian cows under Egyptian conditions to achieved maximum genetic merit.
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