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Description: This file contains eleven images from Dr. T. Y. Tanabe's research on postpartum cows between 1950 and 1955 at Pennsylvania State University, digitized without changes except for the size indicators superimposed. Additionally, the infundibulum (Inf) of the oviduct, ovary (O), endometrial caruncles (C), and a metestrus corpus luteum (CL) on the right ovary (image 3a) have been labeled on images 1 and 3 to create 1a and 3a. In each image, the uterus, cervix and vagina had been opened dorsally to reveal their lumenal surfaces. Each of these images was captured within a few days following the first or second (images 6, 10 and 11) estrus after parturition, the postpartum day of the estrus recorded below each image. Ovarian activity (follicles and/or corpus luteum) is evident in each image. During parturition, chorionic cotyledons pull away from the endometrial caruncles, and the extra-embryonic membranes normally are expelled within about 6 hours after the calf is born. The extent of the remodeling occurring during uterine involution is evident from a comparison of these images with those in NAL 3487 and 3488 that illustrate cotyledons during pregnancy. Images 2, 5, 7 and 8 demonstrate that parturition also can damage the cervix and vagina. Although estrous cycles had commenced in all of these cows, the endometrial caruncles were not completely regressed in any of them, even at 52 days. Nevertheless, pregnancy can be initiated during this period, albeit at reduced rates. Breeding dairy cattle is usually avoided during this period, in part because of the negative energy balance accompanying increasing demands of lactation. In contrast, in beef cattle breeding often is initiated within 30 to 60 days in an effort to maintain annual calving.

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