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- Nilforooshan, Mohammad A., et al.
(author)
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Application of a multiple-trait, multiple-country genetic evaluation model for female fertility traits
- 2010
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In: Journal of Dairy Science. - : American Dairy Science Association. - 0022-0302 .- 1525-3198. ; 93, s. 5977-5986
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Journal article (peer-reviewed)abstract
- The need to implement a method that can handle multiple traits per country in international genetic evaluations is evident. Today, many countries have implemented multiple-trait national genetic evaluations and they may expect to have their traits simultaneously analyzed in international genetic evaluations. Traits from the same country are residually correlated and the method currently in use, single-trait multiple across-country evaluation (ST-MACE), cannot handle nonzero residual correlations. Therefore, multiple-trait, multiple across-country evaluation (MT-MACE) was proposed to handle several traits from the same country simultaneously. To test the robustness of MT-MACE on real data, female fertility was chosen as a complex trait with low heritability. Data from 7 Holstein populations, 3 with 2 traits and 4 with 1 trait, were used. The differences in the estimated genetic correlations by MT-MACE and the single ST-MACE analysis (average absolute deviation of 0.064) were due to the bias of considering several traits from the same country in the ST-MACE analysis. However, the differences between the estimated genetic correlations by MT-MACE and multiple ST-MACE analyses avoiding more than one trait per country in each analysis (average absolute deviation of 0.066) were due to the lack of analysis of the correlated traits from the same country together and using the reported within-country genetic correlations. Applying MT-MACE resulted in reliability gain in international genetic evaluations, which was different from trait to trait and from bull to bull. The average reliability gain by MT-MACE over ST-MACE was 3.0 points for domestic bulls and 6.3 points for foreign bulls. Even countries with 1 trait benefited from the joint analysis of traits from the 2-trait countries. Another superiority of MT-MACE over ST-MACE is that the bulls that do not have national genetic evaluation for some traits from multiple trait countries will receive international genetic evaluations for those traits. Rank correlations were high between ST-MACE and MT-MACE when considering all bulls. However, the situation was different for the top 100 bulls. Simultaneous analysis of traits from the same country affected bull ranks, especially for top 100 bulls. Multi-trait MACE is a recommendable and robust method for international genetic evaluations and is appropriate for handling multiple traits per country, which can increase the reliability of international genetic evaluations.
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| 3. |
- Nilforooshan, Mohammad A.
(author)
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Contemporary grouping in mixed-size dairy herds experiencing four seasons
- 2010
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In: Tu¿¿¿¿rk Veterinerlik Ve Hayvanc¿¿¿¿l¿¿¿¿k Dergisi =. - : The Scientific and Technological Research Council of Turkey (TUBITAK-ULAKBIM) - DIGITAL COMMONS JOURNALS. - 1300-0128 .- 1303-6181. ; 34, s. 129-135
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Journal article (peer-reviewed)abstract
- Countries with different herd structures and climates use different combinations of herd, year, and season to define the effect of their climatic conditions and management. Estimates of variance components and Akaike information criterion values resulting from 8 analytical models differentiated by different combinations of herd, year and season effects were compared for milk and fat yields. Data consisted of pedigree and records of 11,850 Holsteins freshening in 38 dairy herds of Isfahan, Iran, between January 1994 and October 2001. Heritability estimates were lowest for the models that used herd-year combination as a random effect. Moreover, the use of these models is not recommended due to their low goodness of fit, at least for countries that have too much variety in herd size. The models that considered herd-year or herd-year-season as a fixed effect to define contemporary groups fit the data best. It is worthwhile rechecking the frequency of animals in herd-year-season groups in order to control the minimum number of animals in contemporary groups. Countries with 4 seasons and small herds may consider herd-year and 4-month season as 2 separate fixed effects to observe contemporary groups sufficiently and to make a better correction for seasonal changes or considering herd-year-season as a random effect.
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| 4. |
- Nilforooshan, Mohammad A.
(author)
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Developing the method of estimating genetic similarity between populations
- 2009
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In: Annual meeting of the European Association for Animal Production. - 1382-6077. ; , s. 610-610
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Conference paper (other academic/artistic)abstract
- An existing method for measuring genetic similarity between populations was further developed to include information from ancestors. Genetic similarity is the extent of genetic exchange or the amount of the genetic material that is shared between the gene pools of two populations. Genetic correlations and the number of exchanged individuals have been used traditionally as indicators of genetic similarity. However, genetic correlations are trait-dependent and under the influence of genotype by environment interaction and the number of exchanged individuals do not show the extent of spreading genes from exchanged individuals into two populations. The present method uses the number of progenies from the shared individuals in the two populations without using the parental information of the shared individuals. With the new method, most of the pedigree information is capture without the need to use a relationship matrix. Therefore, it is easy to implement and has a low computational demand. This new method can be used in studies of biodiversity or screening of populations for which genetic correlations are going to be estimated.
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| 6. |
- Nilforooshan, Mohammad A., et al.
(author)
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MT-MACE for female fertility and milk yield
- 2009
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In: Bulletin / International Bull Evaluation Service. - 1011-6079. ; 40, s. 68-71
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Conference paper (other academic/artistic)
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| 7. |
- Nilforooshan, Mohammad A.
(author)
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Multiple-trait multiple country genetic evaluation of fertility traits in dairy cattle
- 2011
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Doctoral thesis (other academic/artistic)abstract
- Female fertility is one of the most economically important traits for the dairy cattle industry. Because of a few decades of selection mainly for higher milk production, many dairy farms around the world suffer from the consequences of female fertility loss. The aims of this thesis were to study the international genetic evaluation of female fertility traits, to quantify the bias of analyzing multiple female fertility traits per country with the current method in use for international genetic evaluations (MACE), to study the implementation of a new method (MT-MACE) for the analysis of multiple traits per country, and also to study the effect of across country selection for milk yield on the international genetic evaluation of female fertility traits, when MT-MACE is applied. Female fertility traits are low heritable, each describing a part of the female fertility complex. International genetic evaluation is useful for improving the accuracy of female fertility evaluations and making the across country comparisons of bulls possible. Despite the low heritability values of female fertility traits, the estimated across country genetic correlations were moderate to high, making the international genetic evaluations feasible for female fertility traits. Results for female fertility traits showed that including multiple traits per country in a MACE analysis would lead to considerable bias. This bias is due to ignoring covariances from multiple-trait national models. Avoiding bias by performing several unbiased MACE analyses, each including one trait per country is not advantageous, because it is computationally prohibitive and it does not make an optimal use of the available data. MT-MACE was applied to female fertility data, which led to higher reliabilities compared to the (unbiased) MACE evaluations. The reliability gains were larger for foreign bulls and the Top 100 bulls in each country-trait. The results showed that when the within country selection for milk yield is already taken care of by the multiple-trait national models, the across country selection for milk yield did not make significant bias in the international evaluation of female fertility traits.
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| 8. |
- Nilforooshan, Mohammad A., et al.
(author)
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Multiple-trait multiple-country genetic evaluation of Holstein bulls for female fertility and milk production traits
- 2014
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In: Animal. - 1751-7311 .- 1751-732X. ; 8, s. 887-894
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Journal article (peer-reviewed)abstract
- The aim of this study was to investigate the effect of including milk yield data in the international genetic evaluation of female fertility traits to reduce or eliminate a possible bias because of across-country selection for milk yield. Data included two female fertility traits from Great Britain, Italy and the Netherlands, together with milk yield data from the same countries and from the United States, because the genetic trends in other countries may be influenced by selection decisions on bulls in the United States. Potentially, female fertility data had been corrected nationally for within-country selection and management biases for milk yield. Using a multiple-trait multiple across-country evaluation (MT-MACE) for the analysis of female fertility traits with milk yield, acrosscountry selection patterns both for female fertility and milk yield can be considered simultaneously. Four analyses were performed; one single-trait multiple across-country evaluation analysis including only milk yield data, one MT-MACE analysis including only female fertility traits, and one MT-MACE analysis including both female fertility and milk yield traits. An additional MT-MACE analysis was performed including both female fertility and milk yield traits, but excluding the United States. By including milk yield traits to the analysis, female fertility reliabilities increased, but not for all bulls in all the countries by trait combinations. The presence of milk yield traits in the analysis did not considerably change the genetic correlations, genetic trends or bull rankings of female fertility traits. Even though the predicted genetic merits of female fertility traits hardly changed by including milk yield traits to the analysis, the change was not equally distributed to the whole data. The number of bulls in common between the two sets of Top 100 bulls for each trait in the two analyses of female fertility traits, with and without the four milk yield traits and their rank correlations were low, not necessarily because of the absence of the US milk yield data. The joint international genetic evaluation of female fertility traits with milk yield is recommended to make use of information on several female fertility traits from different countries simultaneously, to consider selection decisions for milk yield in the genetic evaluation of female fertility traits for obtaining more accurate estimating breeding values (EBV) and to acquire female fertility EBV for bulls evaluated for milk yield, but not for female fertility.
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