Subclinical selenium insufficiency [in sheep], 2. The response in reproductive performance of grazing ewes supplemented with selenium
1991
Langlands, J.P. | Donald, G.E. | Bowles, J.E. | Smith, A.J. (Commonwealth Scientific and Industrial Research Organisation, Armidale (Australia). Div. of Animal Production)
Merino and Border Leicester cross ewes were grazed for 4 years on improved pastures at 2 stocking rates, and some were supplemented with intraruminal Se pellets. The incidence of oestrus was not affected by differences in stocking rate, genotype or Se level. On mating to Merino and Dorset Horn rams, respectively, fertility was unaffected by treatment, but fecundity was higher in crossbreds, though not affected by stocking rate or Se. Survival of lambs was increased by Se at the high stocking rate only. A complex interaction between genotype, litter size and Se indicated that Merino singletons responded more to Se than twins, while the reverse was the case with crossbreds. Number of lambs weaned per ewe increased with Se at the high stocking rate, and decreased at the low. It is suggested that response to Se supplements is sensitive to factors other than the level of Se.
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