Effects of Embryo-Transfer, Recipient-Donor Mother and Environment on Lamb Weaning Weight and Variance Components


Abstract: Factors affecting lamb weaning weight (WW) and the (co)variance components due to direct and maternal effects on weight were investigated using a small data set based on ewes involved in an embryo transfer trial. Records of 253 Welsh Mountain lambs for adjusted 50 day weaning weight were obtained from the nucleus flock of the CAMDA co-operative breeding scheme. DFREML was used for variance component analyses. Significant fixed effects included in the model were rearing dam age, sex, rearing type and year. Six different models were used to analyse variance components. Obtained h^2 walues from the models were 0.104, 0.034, 0.057, 0.044, 0.035 and 0.485 respectively. The main value of these data sets based on embryo transfer data is their emphasis on a large number of progeny from genetic dams. However, there are potential disadvantages associated with the small size of the data set and limited information on rearing dams. The results highlight the importance of rearing dams and suggest that the use of high quality dams as donors and low quality dams as recipients may not yield a practical system if good growth into weaning is desired.

Keywords: Lamb, embryo transfer, maternal effect, variance components, weaning weight

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