SummaryAn histological examination of the female reproductive tract showed that all parts of the tract undergo cyclical changes. In general the height of the lumenal epithelium reaches a maximum during oestrus and secretory activity also appears to be maximal at this time.Secretory cells were not seen in the vagina. The cervix, however, had an epithelium continually containing mucus-secreting cells. This mucus was released into the cervical lumen during pro-oestrus and oestrus. The glands of the uterus exhibited secretory activity during pro-oestrus, but it is not clear whether the lumenal epithelium has any secretory function. The fallopian tubes showed evidence of continual secretion, concentrated mainly in the ampulla region. As well, the degree of mucosal folding increased greatly from the isthmic region to the ampulla region. INTRODUOTIONThe histological changes occurring in the female reproductive tract have been studied in many species (Snyder 1923;Novak and Everett 1928;Grant 1934;Roark and Herman 1950;Hadek 1955). In the sheep, reports of cyclical changes in the intact female reproductive tract are scant and some disagreement exists as to the nature of the changes and their time relationship to the oestrous cycle (Casida and McKenzie 1932;Grant 1934;Cole and Miller 1935;Hadek 1955Hadek , 1958.Before undertaking further studies of the female reproductive tract it was deemed necessary to investigate the cyclical changes occurring in the breed of sheep to be studied, namely the Merino. At the same time it was thought desirable to express these changes in a quantitative manner, a task not undertaken before in this species. II. MATERIALS AND METHODS (a) AnimalsThirty-seven mature Merino ewes of similar origin were used. (b) TreatmentA large flock of ewes were run with raddled, vasectomized rams overnight, and the raddled ewes were discarded. The flock was reteased for the next 22 hr and 37 raddled ewes were obtained for study. These 37 ewes were run with raddled, teaser rams continuously for the remainder of the trial period. Two ewes were slaughtered at each of the following time intervals after first being marked (day of marking is day 1): 1,2, 3,4,5,6,8,10,12,14,15,16,17,18,19,20,21 days. It was noted if the ewes were remarked before slaughter. (c) Collection of Reproductive TractsThe ewes were slaughtered and placed on an abattoir chain. The entire reproductive tract was removed within 20 min of death, examined, and placed in a buffered formalin fixative (pH 7 ·4). HISTOLOGY OF THE REPRODUCTIVE TRACT OF THE EWE (d) Classification of Reproductive TractsAfter consideration of the time of slaughter and the ovarian morphology (Restall 1964), each tract was classified as being in oestrus, metoestrus, dioestrus, or pro-oestrus. Metoestrus was arbitrarily considered to extend for 5 days and ovulation was considered to occur toward the end of oestrus. The classifications are given in Table 1.( e) I'reatment of Reproductive TractsSome butchers removing the tracts from the ewes often damaged them such that they ...
In two experiments, Merino ewes that had lambed in either the autumn or spring were treated with various combinations of a progestagen (methylacetoxyprogesterone, MAP) and pregnant mare's serum gonadotrophin (PMSG), from 3 days post partum. Irrespective of the season of lambing, the treatments resulted in ovulation in nearly all ewes before day 15 post partum; oestrus was observed in all ewes that had lambed in the autumn but in only half the spring ewes. Regular oestrus activity was not resumed after the induced oestrus and/or ovulation. After further treatments with MAP and PMSG (days 15–26 post partum), 29% of the ewes showed oestrus (autumn and spring), with 47.1% and 58.3% of ewes ovulating in the autumn and spring respectively. Cystic and/or persistent corpora lutea (CP) were noted in 24% of the treated ewes. In spring-lambing ewes, 42% of ovulations before day 15 were judged to be abnormal. Fertilization rates were low in ewes that mated. The best results, 56% of ova fertilized, were from matings between 26 and 30 days post partum in spring-lambing ewes. In two further experiments, the fertility of ewes was examined at matings induced at various times post partum in crossbred ewes that had lambed in the spring. The fertility was low (=17%) up to 30 days post partum, but it improved in later matings (=30%). The incidence of a second oestrus succeeding the induced cycle was low (29%), but fertility was higher (50%). Approximately 50% of the untreated ewes lambed to matings between 30 and 60 days after lambing.
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