Characterization of uterine leukocyte infiltration in gilts after artificial insemination

The objective of this study was to characterize the uterine leukocyte influ x after artificial insemination (AI). After detection of oestrus with a boa r at intervals of 1.5 h, seventy-two gilts were randomly assigned to a 2 x 3 x 4 factorial arrangement. AI was performed with 100 mi extended semen co ntaining 5 x 10(9) spermatozoa (semen; n = 36) or 100 mi VSP semen extender (extender; n = 36) at one of three times after detection of oestrus: 12, 2 4 or 36 h (n = 24 / time). The uterus was lavaged at 6, 12, 18 or 24 h (n = 18 / time) after AI to determine the total number of uterine leukocytes. I n addition, uterine lavage was performed on nine untreated gilts immediatel y after the detection of oestrus to establish a baseline number of leukocyt es. The leukocyte response in all samples consisted predominately (92-99%) of polymorphonuclear neutrophilic granulocytes (PMNs). The mean number of P MNs recovered from the uteri of gilts treated with semen was greater than i n gilts treated with extender and in untreated gilts (P < 0.01). The greate st number of PMNs in semen-treated gilts was found 12 h after Al (P < 0.01) , and this number was sustained for 24 h. In contrast, the number of uterin e PMNs recovered from extender-treated gilts reached a peak at 6 h and had declined by 12 h after AI (P < 0.05). It was concluded that an extensive in flux of PMNs into the uterus is a normal sequence to AI. The consequences a nd importance of semen-induced uterine leukocytosis needs further investiga tion.