INBREEDING IN THE ELSENBURG DORMER SHEEP STUD

Data of the Elsenburg Dormer sheep stud which was kept closed since it s inception, were collected over a period of 50 years (1941-1990). The se data were analysed to monitor the increase in actual level of inbre eding and to investigate the effect of inbreeding on some early growth and reproduction traits. In total, 9551 pedigree, 8963 birth weight a nd 7 782 weaning weight records were available. The average level of i nbreeding of all animals over all years was 15%. At the end of the stu dy the average inbreeding coefficient in the population was 20.5% with a minimum of 18.2% and maximum of 26.3%. The regression coefficients of lamb inbreeding on birth weight (BW), weaning weight (WW), average daily gain (ADG) and Kleiber ratio (ADG/WW0.75) were -0.008, -0.099, - 0.0009 and -0.021, respectively. All these coefficients differed signi ficantly (P < 0.01) from zero. Inbreeding of the dam had no significan t effect on these traits. No significant effect of lamb or dam inbreed ing on average litter size (lambs born/ewe lambing), survival rate (la mbs weaned/lambs born) and stillbirths was observed.