Abstract
The macroscopic appearance of the reproductive tract of second-litter lactating sows was observed at 1, 3, 7, 14, 21, 28, 35, 45, 52, and 62 days after farrowing. In addition, observations were made on the reproductive organs of sows 1, 2, 3 and 4 days after being weaned subsequent to an 8-week lactation period. A total of 67 sows were slaughtered for examination. The uterus decreased in weight and length until day 28 after parturition, then changed little for the remainder of the lactation period. During the 4 days immediately after the pigs were weaned the uterus increased in both weight and length. The data suggest that the uterus of the sow completes involution at between 21 and 28 days after farrowing. Corpora lutea of pregnancy, which averaged 8.1 mm. in diameter at day 1 after parturition, rapidly decreased in size and appeared only as dark brown spots or streaks in the ovarian stroma by the end of the lactation period. The follicles, which averaged 4.6 mm. in diameter 1 day after parturition, decreased significantly (P<.01) in size during the first week after parturition. At 3 and 4 days postweaning a marked increase in follicular size occurred. The same trend in ovarian follicular development was indicated by the number of follicles 5.0 mm. or greater in diameter present at various intervals after parturition and weaning. Copyright © 1965. American Society of Animal Science . Copyright 1965 by American Society of Animal Science