tailieunhanh - Báo cáo sinh học: "Heterogeneity of variance components for preweaning growth in Romane sheep due to the number of lambs reared"

Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học quốc tế đề tài: Heterogeneity of variance components for preweaning growth in Romane sheep due to the number of lambs reared | David et al. Genetics Selection Evolution 2011 43 32 http content 43 1 32 Ge n et i cs Selection Evolution RESEARCH Open Access Heterogeneity of variance components for preweaning growth in Romane sheep due to the number of lambs reared 1 2 I- 1 13 4 Ingrid David Frédéric Bouvier Dominique Franqois Jean-Paul Poivey 1 and Laurence Tiphine Abstract Background The pre-weaning growth rate of lambs an important component of meat market production is affected by maternal and direct genetic effects. The French genetic evaluation model takes into account the number of lambs suckled by applying a multiplicative factor 1 for a lamb reared as a single for twin-reared lambs to the maternal genetic effect in addition to including the birth rearing type combination as a fixed effect which acts on the mean. However little evidence has been provided to justify the use of this multiplicative model. The two main objectives of the present study were to determine by comparing models of analysis 1 whether pre-weaning growth is the same trait in single- and twin-reared lambs and 2 whether the multiplicative coefficient represents a good approach for taking this possible difference into account. Methods Data on the pre-weaning growth rate defined as the average daily gain from birth to 45 days of age on 29 612 Romane lambs born between 1987 and 2009 at the experimental farm of La Sapinière INRA-France were used to compare eight models that account for the number of lambs per dam reared in various ways. Models were compared using the Akaike information criteria. Results The model that best fitted the data assumed that 1 direct maternal effects correspond to the same trait regardless of the number of lambs reared 2 the permanent environmental effects and variances associated with the dam depend on the number of lambs reared and 3 the residual variance depends on the number of lambs reared. Even though this model fitted the data better than a model that included a .