Short-term dietary effects on reproductive wastage after induced ovulationand artificial insemination in primiparous lactating Sarda ewes

Short-term effects of nutrition on conception rate (CR), ovulation rate (OR ), ova and embryo losses (OEL) during the first 50 days following inseminat ion and total reproductive wastage after ovulation (TRW), were investigated in primiparous lactating Sarda ewes after oestrous synchronisation and tra ns-cervical artificial insemination (AI). Eighty ewes grazing a green high- quality pasture were offered one of three iso-energetic supplements from da y 14 before to day 2 after AI: whole maize grain (M); soyabean meal (S); ma ize gluten meal (G); or served as controls (C). Supplements G and S were is o-nitrogenous but provided different amounts of rumen undegradable digestib le protein. The intake of herbage and digestible dry matter, measured by th e n-alkane method, did not differ among groups, whereas crude protein intak e before Al was greater in S and G than in M and C. Average OR was 2.0 per ewe. The frequency of double ovulations was greater in S than in the other groups. Only G-feeding was associated with some cases of OR > 4. Ewes from the S group tended to show a higher CR (73%) than unsupplemented counterpar ts (45%), the other groups bring intermediate (61% and 50% for M and G, res pectively). Lower OEL during the first 50 days after Al was found in S ewes than in G, M and C being intermediate (0.52, 1.39, 1.11 and 1.10 per ewe, respectively). Milk urea content > 560 mg/l was associated with lower CR. R anking by ovulation groups of CR was single < double = triple; and of TRW w as double < triple < single. In conclusion, OR in primiparous lactating Sar da ewes grazing on a good quality pasture is high, and CR after AI is reduc ed by ova as well as embryo loss, especially following single ovulations. S hort-term supplementation with a soyabean-based concentrate may help allevi ate these losses. (C) 2000 Elsevier Science B.V. All rights reserved.