Genetic analysis of wool shedding scores of ewes from a composite flock using a threshold model and Bayesian methodologies

Abstract Text: Data were collected on 1608 ewes from a composite flock (Dorper, Katahdin and Romanov) over a 4 year period, including a total of 3346 records and a pedigree file containing 9895 individuals. Wool shedding scores (WSS) were considered a categorical (ordinal) trait with 0, 1 less than 25% of wool coverage (WC), 2 to 6 between to 25 and 75% of WC, and 7, 8 more than 75% of WC. A Bayesian analysis using the RJMC module from the DMU software package was used to fit a probit threshold model. Heritability and repeatability of liability of WSS were moderate at 0.33 ± 0.02 and 0.48 ± 0.02, respectively. The heritability estimated was similar to those reported in the literature. Based on chi-squared tests, age and birth-rearing type influenced WSS (P < 0.001).

Keywords: wool shedding, MCMC, heritability