Yearling and ewe fleece weights in Romney and Perendale flocks selected for divergence in faecal nematode egg count.

Abstract

Three selection experiments in New Zealand, two involving Romneys (at Wallaceville and Ruakura) and the third involving Perendales (at Ruakura), have resulted in breeding lines showing significant divergence in faecal nematode egg count (FEC), following natural challenge. The pair of High and Low FEC lines in each experiment has experienced 18, 8 and 11 years of selective breeding respectively. In the present study, the High and Low lines are compared for greasy fleece weights in both yearlings and mixed-age ewes (YFW and EFW). Relative to the Low lines, the corresponding High lines had greater YFWs by 14.6+3 .O, 7.922.4 and 5323.1% respectively (mean of three, 9.1+1.6%), and they had greater EFWs by 11.722.1, -3.2i3.8 and 8.0+2.7% (mean of three, 8.2+1.50/o). The conclusion is that selection for reduced FEC in Romneys and Perendales is associated with reduced greasy fleece weight, when animals graze together.