PARAMETER ESTIMATES FOR DIRECT AND MATERNAL GENETIC EFFECTS FOR MILK .YIELD TRAITS IN A FRIESIAN CATTLE HERD IN EGYPT | ||||
| Journal of Animal and Poultry Production | ||||
| Article 1, Volume 31, Issue 5, May 2006, Page 2663-2669 PDF (510.5 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jappmu.2006.235474 | ||||
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| Author | ||||
| M. N. EI-Arian | ||||
| Animal Production Department, Faculty of Agriculture, Mansoura University. | ||||
| Abstract | ||||
| Data on 2161 normal lactation records of Friesian cattle raised at an experimental station during the period from 1996 to 2002 were used. Number of sires and dams were 92 and 878. respectively .Data were analyzed using MTDFREML program. Two animal models were fitted .Model 1 considered the animal (additive direct genetic effects) and the permanent environmental effects as a random effect. Model 2. the maternal genetic effects was added to Model 1. which allowed for the estimation of the genetic covariance between the direct and maternal genetic effects. In the two models fitted. the fixed effects were month and year of calving and parity. Age of cow at calving was included as a covariate. Direct and maternal genetic effects and genetic parameters for 305 day milk yield (MY). 305day fat yield (FY) and 305 day protein yield (PY) were estimated. Estimate of direct heritability of the mentioned traits was 0.26. 0.24, and 0.26. respectively using Model 1. and 0.31. 0.34. and 0.40. respectively using Model 2. Maternal heritability estimate was 0.01. 0-06 and 0.13. respectively. Permanent environmental variance as a proportion of phenotypic variance was 0.03. 0.11 and 0.11. respectively (Model 1) and 0.12. 0.12 and 0.10. respectively. (Model 2) .Estimates of genetic correlations between direct and maternal genetic effects for all milk yield traits studied were negative and ranging from - 0.36 to — 0.18. Direct genetic correlation between these traits was positive and high. ranging from 0.95 to 1.00 for Model 1 and from 0.85 to 0.96 for Model 2. Results of the present study. indicated that the inclusion of maternal genetic effects in the model of analyses for milk yield traits. is recommended. as. it leads to higher estimates for genetic parameters. | ||||
| Keywords | ||||
| Genetic parameters. direct and maternal genetic effects; direct heritability. maternal heritability. genetic correlation. milk yield traits. Friesian cattle | ||||
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