Short-term dietary effects on reproductive wastage after induced ovulation and 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 insemination and total reproductive wastage after ovulation (TRW), were investigated in primiparous lactating Sarda ewes after oestrous synchronisation and trans-cervical artificial insemination (AI). Eighty ewes grazing a green high-quality pasture were offered one of three iso-energetic supplements from day 14 before to day 2 after AI: whole maize grain (M); soyabean meal (S); maize gluten meal (G); or served as controls (C). Supplements G and S were iso-nitrogenous but provided different amounts of rumen undegradable digestible protein. The intake of herbage and digestible dry matter, measured by the n-alkane method, did not differ among groups, whereas crude protein intake 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 counterparts (45%), the other groups bring intermediate (61% and 50% for M and G, respectively). 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. Ranking by ovulation groups of CR was single < double = triple; and of TRW was double < triple < single. In conclusion, OR in primiparous lactating Sarda ewes grazing on a good quality pasture is high, and CR after AI is reduced by ova as well as embryo loss, especially following single ovulations. Short-term supplementation with a soyabean-based concentrate may help alleviate these losses. (C) 2000 Elsevier Science B.V. All rights reserved.