tailieunhanh - báo cáo khoa học: "On the estimation of genetic parameters components via variance"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: On the estimation of genetic parameters components via variance | c Génét. Sél. Evol. 1983 15 3 425-444 On the estimation of genetic parameters via variance components L. DEMPFLE c. HAGGER and M. SCHNEEBERGER Lehrstuhl fur Tierzucht der TU Munchen D-8050 Freising-Weihenstephan Germany Institut of Animal Production Swiss Federal Institut of Technology CH-8092 Zurich Switzerland Herd Book Office for Swiss Braunvieh CH-6300 Zug Switzerland Summary Variance components have been estimated by three methods using two different but overlapping data sets from a dairy cattle breeding scheme. The methods were Henderson s method III MINQƯE and a new method proposed by Henderson in 1980. Two different statistical models of grouping sires were considered. For all methods the exact variances of the estimators were calculated for given true variance components and assuming normality of the data. As a byproduct the large sample variances of REML were obtained. A short discussion of the interpretation of the two estimated variance components is given for the two statistical models taking selection into account. A concise description is given of the three estimation methods employed. For a relatively simple model it is shown that they use different weighting factors for combining means and squares. The new method proposed by Henderson 1980 has two possible disadvantages namely fewer degrees of freedom for estimating the error variance and one deriving from the relationship with the method of contemporary comparison. From this limited investigation it is concluded that in situations where the method might be employed these disadvantages may not be of great importance. The numerical results of the estimation with the two statistical models lie reasonably well within the expected range. A noteworthy difference in efficiency was found between MINQUE and Henderson s method HI in favour of MINQUE given that a reasonable prior estimate of the ratio of the error component to the sire variance component was used in the estimation. As expected the new method

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