BRIEF COMMUNICATION: High crude protein in autumn pasture does not impair reproductive performance in sheep

Abstract

Embryos exposed to ammonia may degenerate or their growth enhanced (McEvoy et al., 1997). Kelly (1982) reported reproductive wastage of 24.9% in South Island sheep. New Zealand pastures contain high concentrations of crude protein (Chaves et al., 2002) but whether reproductive wastage can partly be explained by ammonia and/or urea toxicity from high protein pasture is unknown. The aims of the present study were to determine the effect of plasma urea concentration on ovulation rate, embryo survival, conception rate and lamb birth weight in ewes joined with the ram on high protein pasture.