Histological Changes in the Reproductive Tract of the Sow during Lactation and Early Postweaning2

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Abstract
Tissues were obtained from the ovary, uterus, oviduct, cervix and vagina from a total of 67 second-litter sows during lactation and early postweaning. Corpora lutea of pregnancy in the sow promptly degenerated after parturition and by the 7 th day were composed mainly of connective tissue. Atretic follicles appeared more numerous in the ovaries of sows during the immediate postpartum intervals. Ovulation did not occur in any of the sows observed throughout the 62-day lactation period, but occurred in some animals by the third postweaning day. Uterine epithelium appeared to be degenerate during the immediate postpartum period, then underwent regeneration which began at 7 days postpartum and appeared to be complete by the 21st day. The epithelium was low columnar or pseudostratified in appearance from 21 days after farrowing throughout the remainder of lactation. Increased epithelial height and glandular development occurred at 3 and 4 days postweaning. The epithelium of the oviduct was tall and pseudostratified immediately postpartum and at 3 and 4 days postweaning. It was low columnar in outline and was studded with finger-shaped cytoplasmic protrusions from 7 days postfarrowing throughout the remainder of lactation. Cervical epithelial cells were tall columnar in type and contained aldehyde-fuchsin positive material at 1 and 3 days postpartum and at 3 and 4 days postweaning. During the remainder of the period under study they were low columnar or pseudostratified with no aldehyde-fuchsin reaction. The stratified squamous vaginal epithelium was five to eight cell layers thick 1 day postpartum, decreased to two or three layers at 14 days postpartum, then increased from the 45 th day postpartum to 12 to 15 cell layers at 4 days postweaning. Copyright © 1965. American Society of Animal Science . Copyright 1965 by American Society of Animal Science

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