Estimation of Genetic Trends of Reproductive Traits of Iranian Holstein Cattle by Animal Model with Genetic Groups

Shatteri, A. R. (2014) Estimation of Genetic Trends of Reproductive Traits of Iranian Holstein Cattle by Animal Model with Genetic Groups. Masters thesis, University of Zabol.

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Genetic improvement of livestock through breeding (select superior animals as next generation parents), is a sustainable approach to increase animal production. The success rate of breeding depends on the role of genetics in making differences between animals, identify animals with desired genotypes, and the selection for the next generation parents. Each progress on animal's economic traits takes place in according to the availability of genetic information, the usage of appropriate selection methods and genetic trends estimation. It should be noted that animal genetic structures is influenced by genetic process and it will be different by years that will cause doubts in genetic basis variance homogeneity assumptions; hence, using an animal model with the effects of genetic groups may be able to consider the effects of animals with unknown pedigree. The registered records of National Livestock Breeding Center (1346 to 1392) were used. Data preparation and analysis were down by R-3-2. Reproductive traits were the interval between calving to first service (CTFS), the interval between first service to conception (FSTC), calving interval (CI). The analysis of genetic parameters showed the effect of genetic groups in variance analysis decrease genetic variances and standard errors of all traits in three lactating periods; as the residual variance do too. The heritability of CI and CTFS were decreased by affecting genetic groups in the model, but had no effects on FSTC and obtained constants numerical results (0.003). According to the obtained results, the estimation of spearman correlation changes in this traits between model 1 (animal model without genetic groups) and model 2 (animal model with genetic groups) had a significant effect (p<0.0001). Therefore, it was determined the slight changes in the variance components between model 1 and 2 had a significant effect on the animals ranking, and also it had a reduction trend from first to third calving period. The mean of standard error and the accuracy of breeding values was significant (p<0.001) in both models evaluations of all traits. Most of results obtained in model 1 were less than model 2, but there were no systematic trends in different calving periods of desired traits. The results of genetic trends show that all traits except of FSTC, had a reduction in their trends of both models, otherwise, estimated values (both negative and positive) of model 2 for all three traits were higher than estimated values in model1.

Item Type: Thesis (Masters)
Subjects: S Agriculture > SF Animal culture
Depositing User: admin admin1 admin2
Date Deposited: 19 Jun 2016 04:44
Last Modified: 19 Jun 2016 04:44

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