Estimating the binding ability of collared peccary (Pecari tajacu Linnaeus, 1758) sperm using heterologous substrates

In collared peccaries, the development of artificial insemination (AI) is scarce, requiring search for alternative methods for the evaluation of sperm fertilizing ability. Thus, the aims of this study were to estimate the binding capability of collared peccaries sperm, using swine oocytes and the egg perivitelline membrane, and to evaluate the prognostic value of sperm parameters on the in vitro interactions among sperm and heterologous substrates. Eleven ejaculates were collected by eletroejaculation and evaluated for viability and morphology by light microscopy, for functionality by hypo-osmotic swelling test, for plasma membrane integrity by epifluorescence microscopy, and for sperm motility by computerized analysis. Subsequently, for analysis of the in vitro interactions, sperm samples were cultured in an incubation medium with swine oocytes and egg perivitelline membrane for 18 h and 20 min, respectively, at 38.5 °C and humidified atmosphere. The sperm-oocyte interaction rate was 100% with sperm penetrating 19.8+ 5.5% of oocytes. The average values of bound sperm and penetrated sperm per oocyte were 39.4 + 4.6 and 2.5 + 0.7, respectively. Already for perivitelline membrane binding assay, all samples presented sperm bound (100%) with average of 140.6 ± 19.4 bound sperm (range 33.9-308.7). Moreover, positive correlations were observed for the number of sperm bound to swine oocytes and osmotic response (r = 68.5%; P = 0.02), membrane integrity (r = 65.1%; P = 0.03), and straightness (r = 66.5%; (P = 0.03), as weel as for the number of sperm bound to egg perivitelline membrane and sperm viability (r = 74.0%; P = 0.01), total motility (r = 63.6%; P = 0.04), and linearity (r = 70.5%; P = 0.02). Finally, a negative correlation among slow (r = -80.5%; P = 0.01) and static (r = -84.3%; P = 0.01) sperm with the egg perivitelline membrane was observed. In conclusion, swine oocytes and perivitelline membrane can be used as indicators for the functional evaluation of the binding capability of sperm derived from collared peccaries. These tests could be incorporated into the routine of semen technologies.