The effect of dietary molybdenum and sulphate on sexual activity and plasma progesterone concentrations of ewes

Abstract

The effect of an induced copper (Cu) deficiency on the fertility of South Africa Mutton Merino ewes ( Ovis aries) was investigated. The incidence of oestrus of adult ewes suffering from an induced Cu deficiency by supplementing molybdenum (Mo – 38 mg Mo/kg feed) and sulphur (S – 0.34%) to their diet was compared to that of a control group (Mo – 1.3 mg/kg; S – 0.22%). Although no significant differences in plasma progesterone concentrations were recorded during the oestrus cycles, 75% of the four-to-six-tooth experimental ewes (Cu deficient) stopped showing signs of behavioral oestrus (silent heats) after 6 weeks on the diets (middle May). In Trial 2, 5-month-old ewes ( n = 13) reaching puberty were used. The effects of an induced Cu deficiency on plasma progesterone concentrations, shortly after reaching puberty, were investigated. According to the plasma progesterone concentrations during the oestrus cycle, Cu deficiency resulted in ewes going into a state of anoestrus approximately 2–4 weeks earlier (May–June) at the end of the active breeding season. Although the older ewes (four-to-six-tooth) still ovulated they did not show any signs of oestrus compared to the younger ewes which stopped ovulating.