43 Correlates of reproductive tract anatomy and uterine histomorphometrics with fertility in swine

Abstract

Economic potential of the swine industry hinges upon the reproductive performance of sows, which may be enhanced by improving uterine capacity, a component trait of litter size and piglet productivity. Previous attempts at characterising morphological traits indicative of high uterine volume have not been completely successful, resulting in the continued need for a reliable method of predicting reproductive value to improve production efficiency of the sow. Hence, the main objective of this study was to scrutinize macro- and micro-morphology of the sow’s reproductive tract for quantitative correlations with fertility indices. Reproductive records from Polish Landrace×Polish Large White sows (mean±s.e.m. parity: 4.3±0.6, range: 2–8) were used to examine the associations between fertility and ovarian/uterine morphology (n=34) or uterine histomorphometry (n=10) posthumously. Simple linear regression was performed to determine the relationship between anatomical or histological parameters and various measures of reproductive performance. Several measures related to the ovary, including right and left ovarian weight (r=0.50, P=0.005, and r=0.49, P=0.006, respectively), were positively correlated with the litter size, whereas left ovarian number of corpora lutea (r=−0.38, P=0.04) was negatively correlated with the mean litter size. Analysis of histomorphological characteristics of the uterine wall collected during the luteal phase of the oestrous cycle revealed correlations between mean litter size and myometrial vascular content (r=0.75, P=0.03), the proportion of myometrial stroma (r=−0.68, P=0.03), and the variability of endometrial thickness (r=−0.72, P=0.02) in sows. Eight ovarian, vaginal, and uterine characteristics were significantly correlated with mean lifetime numbers of live born and stillborn piglets/litter or the last litter size before slaughter. In conclusion, several anatomical and histomorphological metrics that relate to reproductive performance of swine may be used to inform production protocols and as a tool for selection of elite breeding sows, warranting future research into noninvasive or minimally invasive techniques for obtaining such measures.