Abstract
The objectives of the study were (a) to study the characteristics of uterine involution in ewes that had developed subclinical uterine infection in the immediately post-partum period and (b) to evaluate effects of the infection in the subsequent reproductive performance of ewes. Uterine infection was induced in ewes (I, n = 10) by intrauterine inoculation of Escherichia coli; uninoculated controls were included (C, n = 12). Animals were examined at regular intervals before and post-inoculation. Clinical and ultrasonographic examinations were performed. Vaginal swab samples and biopsy uterine tissue samples were collected for bacteriological, cytological and histological examination. Finally, ewes were put to rams and reproductive performance was monitored. After challenge, it was ultrasonographically found that caruncular dimensions, myometrial thickness and diameter of uterine lumen were greater in I ewes. In these ewes, particular reduction of dimensions occurred during the second week post-partum, whilst in C ewes during the first week. The uterine artery diameter and the blood flow into the uterus were also greater in I than in C ewes. E. coli infection was more frequent and of longer duration in I than in C ewes: in 68.1% and 50.0% of ewes and 19.5 and 14 days, respectively. There was lower proportion of neutrophils and higher of lymphocytes in group I than in C. In inoculated ewes, there was histological evidence of uterine epithelial destruction, increased cellular infiltration, hyperaemia and extracasation, which persisted up to 42 days post-partum. During the subsequent reproductive season, all ewes in group I lambed normally and produced healthy and viable lambs. No significant difference in reproductive performance parameters were seen in I comparison to C ewes. It is concluded that the innate immunity of the uterus sufficed to counteract the bacterial infection, although the process of involution took longer than in healthy animals; moreover, the ultrasonographic examination is a useful means for assessment of the genital tract of ewes post-partum; finally, no adverse effects were noted in the subsequent reproductive performance of ewes.
Highlights
The puerperium is the period after completion of parturition
Total lambs per ewe During the puerperium, the genital system is returning to its non-pregnant state
We used an established model for inducing uterine infection and its potential effects in uterine regression
Summary
The puerperium is the period after completion of parturition. The period includes many progressive changes in the genital tract for returning to normal pre-gravid state. Noakes [1], in ewes the reduction of the size of the genital tract occurs at logarithmic scale, especially during the first week after lambing. During the 3rd to 10th day post-partum, a rapid reduction in the size of the uterus occurs, which coincides with a decrease in frequency and duration of uterine contractions [1]; other researchers [2,3] have indicated that 50% of uterine reduction was achieved within two weeks after lambing. According to Fernandes et al [4], the reduction in uterine size continued until the 21st day post-partum, but at a slower rate; on the 28th day post-partum, the uterine body diameter was found to be approximately 2 cm. Most relevant studies conclude that uterine involution is complete by the 35th day post-partum (reviewed by Ioannidi et al [5])
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