The relationship between the blood progesterone concentration at early metoestrus and uterine infection in the sow

In a previous study it was shown that gilts inoculated in the uterus during standing oestrus had a better resistance to Escherichia coli infections than gilts that were similarly inoculated within 12 h after the end of the standing reflex (De Winter et al., 1992). In the present study, the changes of blood progesterone concentrations during early metoestrus were investigated. It was also investigated to what extent the onset of endometritis after intrauterine inoculation is correlated to the blood progesterone concentration. In a preliminary study, the plasma progesterone concentration was measured in a group of 11 gilts during early metoestrus, in order to evaluate the average progesterone levels at that stage of the oestrous cycle. A wide variation of blood progesterone concentrations was observed. A second group of 13 gilts was inoculated in the uterus with an E. coli suspension in order to investigate the presence of a correlation between blood progesterone level and susceptibility of the porcine uterus to bacterial endometritis. A third group of six gilts was similarly inoculated with Staphylococcus hyicus. A clear correlation between blood progesterone concentration and susceptibility to endometritis and the development of a vaginal discharge in gilts experimentally inoculated was observed. The gilts with a low blood progesterone concentration at the time of inoculation had less vaginal discharge and a better resistance to endometritis than gilts with a higher blood progesterone concentration. In gilts inoculated with E. coli, as well as those inoculated with S. hyicus, a significant correlation (P < 0.001) existed between the blood progesterone concentration and the development of endometritis. It was concluded that the development of endometritis depends largely on the hormonal environment of the porcine uterus.