The effect of condensed tannins in Lotus corniculatus upon reproductive efficiency and wool production in sheep during late summer and autumn

Abstract

(23 g condensed tannins (CT) /kg DM) and perennial ryegrass-white clover pasture (1 g CT/ kg DM) during the late summer/autumn of 1997 (Experiment 1) and 1998 (Experiment 2). Ewes were in thin condition and weighed 54 kg in Experiment 1 and were fat and weighed 60 kg in Experiment 2. Oestrus was synchronised for two cycles in Experiment 1 and four cycles in Experiment 2. Ewes were grazed at maintenance for the first 10 days of each oestrus cycle and then ad libitum for the last 6 days, including ovulation. Half the ewes grazing L. corniculatus were drenched twice daily with polyethylene glycol (PEG), to inactivate the condensed tannins. Relative to ewes grazing pasture, grazing ewes on L. corniculatus increased both ovulation rate (OR) and wool production, with the response in OR being greater in Experiment 1 (34%) than in Experiment 2 (13%). Maximum increase in OR occurred after grazing lotus for two cycles (5 weeks). Increases in fecundity were caused by a reduction in the proportion of ewes exhibiting single ovulation and increases in the proportions having doubled and triple or quadruple ovulations. As judged by responses to PEG supplementation, part of the L. corniculatus response in OR could be explained by action of CT in Experiment 1 but not in Experiment 2. As voluntary feed intake was similar between the treatments, feeding L. corniculatus improved the efficiency with which ingested nutrients were used for reproduction and wool growth. It was concluded that grazing L. corniculatus during autumn has most potential for increasing OR in lighter ewes. Keywords: condensed tannin, forage, Lotus corniculatus, nutritive value, ovulation rate, wool growth Abbreviations