Increase in chlorine content of cervical mucus as a simple test for impending ovulation and for oestrogenic stimulation in ewes

Abstract

The chloride concentration in the cervical mucus of ewes was estimated by applying a sample of the mucus to paper impregnated with silver chromate. The concentration was equivalent to 0.1-0.3 per cent sodium chloride during dioestrus, rose to 0.7-0.9 per cent about 24 hours before the onset of oestrus and fell to about 0.4 per cent shortly before ovulation occurred. More precise measurements of the ionic concentration of the cervical mucus by a photometric method indicated that the chloride concentration rose from a mean level of 98 m.equiv. per litre (equivalent to 0.6 per cent NaCl) approximately 24 hours before oestrus to 122 m.equiv. per litre (equivalent to 0.7 per cent NaCl) during oestrus; the concentration of sodium increased from 105 to 137 m.equiv. per litre, and potassium decreased from 27 to 14 m.equiv. per litre. The rise in chloride concentration in the mucus was associated with an increase in the amount of mucus present. In ovariectomized ewes an increase in the chloride content of the cervical mucus from 0.1 to 0.7 per cent occurred within 24 hours after either the intramuscular injection of stilboestrol (4 to 20 ¦g) or feeding oestrogenic red clover (0.75 to 3 kg wet weight), and indicates that the method may be useful for rapid oestrogen bioassay in sheep. Progesterone given at the same time, but not when given 48 hours before, depressed the response.