A series of five experiments have been conducted at Massey University to determine whether mid- to late-pregnancy shearing of ewes might provide an opportunity to increase lamb birthweights and enhance survival, particularly of multiple-born lambs, under New Zealand`s pastoral conditions. Although birthweight responses were seen in most studies, they were not consistent with respect to the magnitude of the response or its occurrence in singles vs twins. However, when comparison was made across studies there was a strongly negative relationship between the size of the response and the birthweights of control lambs (those from unshorn ewes). We conclude that responses to mid- to late-pregnancy shearing are likely to be greatest when fetal growth in unshorn ewes is limited by maternal constraint.

PR, Kenyon, ST Morris, DK Revell, and SN McCutcheon

Proceedings of the New Zealand Society of Animal Production, Volume 59, , 70-72, 1999
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