Abstract
The DRB1 intron 2 (GT)(n)(GA)(m) microsatellite was genotyped in experimental flocks of seven Merinoland rams and 249 ewes as well as their offspring (381 lambs) from consecutive lambings. A total of 16 DRB1 alleles were detected, ranging between 353 and 857 bp. In comparison with carriers of other alleles, the ewes carrying the predominant 411 bp allele had higher values of all the recorded fertility traits. For ewes carrying the 394 and 857 bp alleles, the birth weight of lambs was about 400 g higher as compared to the residual group of ewes. The observed associations could be due to differences in disease resistance, cell recognition or tissue differentiation between carriers of various MHC haplotypes which can in turn affect individual fertility and growth performance.