Neutrophil recruitment and phagocytosis of boar spermatozoa after artificial insemination of sows, and the effects of inseminate volume, sperm dose and specific additives in the extender

In this study the recruitment of leucocytes and phagocytosis of spermatozoa after artificial insemination of multiparous sows was investigated. In Expt 1, groups of sows received either no inseminate (n = 6) or inseminates with various concentrations of spermatozoa and seminal plasma or different inseminate volumes (n = 9 per group). In Expt 2, groups of sows received inseminates containing no addition, caffeine + CaCl(2), or excess EDTA (n = 6 per group). Leucocytes and spermatozoa were counted in the collected backflow from the vulva, and in the PBS flushings of the genital tract of sows killed at 4 h after insemination. Tissue homogenates were checked for remaining spermatozoa. Leucocyte recruitment did not depend on the presence of seminal plasma or spermatozoa. In the control groups about 43% of the inseminated spermatozoa were found in the backflow and 5% in the genital tract. Many spermatozoa could be recognized inside polymorphonuclear leucocytes. With an inseminate volume of 20 ml instead of 80 ml, fewer spermatozoa were found in the backflow and more (non-phagocytosed) spermatozoa were recovered in the uterus (P < or = 0.05). With a sperm dose of 0.24 x 10(9) instead of 2.4 x 10(9), a higher percentage of the inseminated spermatozoa was recovered in the oviducts (P < or = 0.05). The use of caffeine + CaCl(2) resulted in lower recruitment of leucocytes (P < or = 0.05) and a higher number of non-phagocytosed spermatozoa in the uterus (P < or = 0.01) compared with controls. The numbers of spermatozoa in the oviducts were not different. Insemination with excess EDTA had no positive effects on the number of spermatozoa in the genital tract.