An investigation of some methods of assessing ovarian activity in swine
Dried smears of cervical mucus collected from sows and gilts during twenty oestrous cycles were examined for arborization. Peak arborization was shown to occur 2 days before the first day of oestrus but individual variations precluded the use of the test for predicting the onset of heat or ovulation. The flow of cervical mucus was found to be greater during pro-oestrus and early oestrus than at other stages of the cycle. Reducing substances in cervical mucus were measured by means of two proprietary indicators. Levels tended to be higher near the beginning of oestrus In most cycles but the degree of the rise and the stage of the cycle at which time i t began were variable. Stained smears of cervical mucus showed epithelial cells and neutrophils in fluctuating proportions throughout the cycle. Large vacuolated epithelial cells were predominant during metoestrus. Biopsies of cervical epithelium were taken at intervals throughout the oestrous cycle of each of two sows and studied histologically. The thickness and mucin content of the stratified columnar epithelium were greatest during oestrus. The possibility of using observations on the arborization of cervical mucus as an aid to pregnancy diagnosis was investigated. The absence of arborization during the third or sixth week after service could be used to diagnose pregnancy. An attempt was made to find a dose of oestradiol benzoate which would induce arborization in the non-pregnant sow but not in the pregnant animal. The oestrogen caused disturbances of the normal cycle and failed to induce arborization during the luteal phase. This approach to pregnancy diagnosis was therefore concluded to be impracticable in swine. The use of observations on cervical mucus as an indicator of oestrogenic activity vas investigated in prepubertal g i l t s and in ovariectomized sows injected vith oestradiol. Neither arborization nor measurement of the amount of reducing substances In cervical mucus could be used to predict the onset of puberty. In ovariectomized animals, the cervix was found to be more sensitive to oestrogens substances in the cervical mucus provided a satisfactory index of the activity of oestrogen alone. A surgical technique of peritoneal cannulation vas developed for repeatedly observing the ovary of the conscious animal.