Abstract

Weaned lambs are often shorn but the limited research on the practice does not demonstrate a clear advantage. As the level of feeding used in some trails may have led to the variable results, experiments investigated the possibility of an interaction between feeding level and lamb shearing. Pasture allowances of 1 kg and 2 kg DM/lamb/d were offered to shorn and unshorn Romney or Coopworth wether and ewe lambs (19 to 28 kg initial live weight) in 2 autumn trials on rotationally grazed irrigated pasture. In the 105-day 1982 trial the shorn and unshorn lambs were grazed together but in the 55 day 1983 trail they were grazed separately. There was an interaction (P<0.01) in 1983 between feeding level and shearing for carcass weight where shorn lambs offered 1 kg DM pasture allowance produced carcasses which were 0.8 kg lighter than the 10.4 kg carcasses for unshorn lambs fed at the same level. Both shorn and unshorn lambs on 2 kg DM allowance produced 11.7 kg carcases. In 1982 shorn lambs had a 10 g/lamb/d faster live-weight gain and 0.5 kg heavier carcasses than unshorn lambs. Carcass weights were 10.6 kg and 12.8 kg at the 1 kg and 2 kg DM feed allowances. The lack of an interaction in 1982, when shorn and unshorn lambs grazed together, may have been caused by shearing inducing an increased appetite in shorn lambs which resulted in competition for feed with the unshorn lambs. In 1982 rates of live- weight gain were 66 and 102 g/lamb/d and in 1983 40 and 110 g/lamb/d from 1 kg and 2 kg DM allowances respectively. These experiments suggest that while lamb shearing may have some management advantages, carcass weights of shorn lambs may suffer if their growth rates are restricted by limited pasture supplies.

KH, Elliott

Proceedings of the New Zealand Society of Animal Production, Volume 44, , 41-44, 1984