Effect of high levels of dietary molybdenum and sulphate on SA Mutton Merino sheep. II. Certain aspects of the oestrous cycle and pregnancy

Forty-five SA Mutton Merino ewes, 2 to 5 years of age, were divided into three groups. Although all ewes received the same basic diet, the diet of one group (group M) was supplemented with molybdenum and that of another group (MS) with molybdenum and sulphate to induce a secondary copper deficiency. The third group (C) served as a control, and received the basic diet supplemented with copper. At the onset of the breeding season (October), oestrus was suppressed by the induced copper deficiency in groups M and MS. Progesterone concentrations in groups M and MS were lower (P ~ 0,05) than that in group C during the oestrous cycle and late pregnancy. Concentration of plasma cholesterol was not affected by the copper deficiency. Concentrations of total plasma copper in both groups M and MS declined during pregnancy whereas that of group C remained constant. Lambs born from ewes in groups M and MS were found to have low concentrations of copper in the plasma (12 f-LgCu/dl) and liver (2-20 f-LgCu/g DM), which resulted in poor growth and a high pre-weaning mortality rate.