Physiology and endocrinology symposium: sperm-oviduct interactions in livestock and poultry.

The Physiology and Endocrinology Symposium titled “Sperm-Oviduct Interactions in Livestock and Poultry” was held at the joint annual meeting of the American Society of Animal Science, American Dairy Science Association, Poultry Science Association, Asociación Mexicana de Producción Animal, and Canadian Society of Animal Science, with partial sponsorship by the EAAP (European Federation of Animal Science), on July 11 to 15, 2010, in Denver, CO. The objective of this symposium was to provide new information on the complicated processes by which the oviduct and sperm interact to lengthen the life span of sperm, regulate sperm maturation, and affect the fertilizing ability of sperm in diverse species, such as livestock and poultry. A comparison between birds and mammals was included to highlight the similar and divergent approaches that female reproductive tracts from different species use to regulate sperm function. The oviduct fulfills several important roles in reproduction. In mammals, it is the place where sperm complete their final maturation (termed capacitation) before fertilizing oocytes. It is also the place where fertilization and early development occur. Fertilization in birds also occurs in the oviduct. After fertilization, the avian oviduct deposits ovalbumen and shell membranes on the ovum. Hence, the oviduct-genital tract has the potential to regulate sperm function and gamete transport by changes in the molecules it secretes and by serving as an adhesive substrate for sperm. The first presentation, provided by Gary Killian, focused on how proteins secreted from the mammalian oviduct affect sperm function (Killian, 2011). Much of the research he discussed used oviduct secretions collected from cows with indwelling catheters placed in the oviduct. The composition and volume of these secretions varies during the estrous cycle because of their hormonal dependence, and differs between the ampulla and isthmus. Killian discussed studies from his laboratory and by others supporting the modulatory effect on sperm function of oviduct glycoproteins, glycosaminoglycans, norepinephrine, catecholamines, heat shock proteins, and osteopontin. For example, oviduct high-density lipoprotein and albumin promote cholesterol efflux from sperm during capacitation. Several oviduct proteins affect sperm by binding to their plasma membrane. The overall effect of oviduct secretions appears to be an increase in sperm viability, motility, and ability to bind the zona pellucida. In most cases, the potential functions of oviduct secretory proteins are unclear. The functions of oviduct-specific glycoprotein and osteopontin were reviewed in more detail. Both bind to sperm and oocytes and promote sperm viability, capacitation, and fertilization when added during in vitro fertilization. Redundant roles for these 2 proteins are supported by the observation that mice deficient in each of these proteins are fertile. Reproduction in birds is vastly different from that in mammals. Birds lack estrous cycles to synchronize copulation with ovulation, so longer term sperm storage is critical. The second presentation, by Murray Bakst, focused on sperm storage in domestic fowl (Bakst, 2011). The domestic and nondomestic birds studied have a specialized region at the upper 2 cm of the vagina, nearest the uterus, called the uterovaginal junction. The surface epithelium of this region forms tubular blind-ended pockets termed sperm storage tubules (SST). The SST store sperm for several days to several weeks, until they are released to ascend the oviduct and fertilize ovulated ova. The SST are formed before the first ovulation and their number varies between species. Sperm ascend the oviduct using their own “mobility,” described by Froman et al. (2011), in addition to being transported by the oviduct. Serotonin-producing endocrine-like cells in the uterovaginal junction may promote localized peristaltic contraction of the vagina and also affect sperm