The effect of dietary molybdenum and sulphate on the oestrus cycle and ovulation in ewes after manipulation with exogenous progesterone alone or in combination with FSH and LH
Sixteen adult South African Mutton Merino ewes (Ovis aries) were divided in two groups. The diet of the experimental animals was supplemented with molybdenum (Mo: 38 mg/kg feed) and sulphur (S: 0.34%) to induce a secondary copper deficiency. Two trials were conducted with four control and four experimental animals in each trial. After synchronisation with progesterone sponges during Trial 1, all the control ewes showed behavioural oestrus with subsequent corresponding ovarian and hormonal reactions. Only one of the experimental ewes showed signs of oestrus. During Trial 2, the ewes were superovulated using progesterone sponges and e-FSH. All control ewes showed signs of behavioural oestrus as opposed to 50% of the experimental animals. The ovarian weight (g) (3.52 ± 0.89 versus 1.50 ± 0.57) and number of follicles (7.52 ± 7.35 versus 14.5 ± 4.93) were reduced (p < 0.05) compared to the control animals. According to the hormonal profiles the progesterone, FSH and LH concentrations were lower (p < 0.05) in ewes suffering from a Cu deficiency compared to control animals. It is suggested that a Mo and S induced Cu deficiency inhibits GnRH release or the production of FSH and/or LH to such an extent that cyclicity in the ewe is suppressed.