Assessment of fertilizing ability of goat spermatozoa by in vitro fertilization of cattle and sheep intact oocytes

Abstract

Intacy oocytes of cattle and sheep were used to study factors that affect the in vitro fertilizing (IVF) ability of goat spermatozoa in vitro. Oocytes were matured in Medium 199 plus estrous sheep serum. Fresh semen was incubated for 4 h at room temperature and spermatozoa were then resuspended in medium Talp plus serum, and were incubated further for 1 h at 39°C in 5% CO 2 in air. Later, spermatozoa were resuspended in Talp plus serum and heparin and were then incubated in microdrops until oocytes were matured. In Experiment 1, the pattern of sperm penetration in matured cattle, sheep and goat oocytes was studied using either residual or standard experimental levels of calcium in the IVF medium. In Experiment 2, the same pattern was studied now by evaluating the sperm penetration rate in cattle oocytes under increasing concentrations of heparin in the IVF medium and then comparing them with those obtained using sheep and goat oocytes. As in Experiment 2, in Experiment 3 the pattern of sperm penetration was studied using increasing concentrations of caffein in the IVF medium. Gametes were incubated for 18 h, and penetration rates were assessed by the presence of pronuclei and sperm tail in the oocyte cytoplasm. The results indicate that 1) the sperm penetration rate in intact cattle, sheep and goat oocytes follows a pathway that depends on calcium; 2) heparin improves the sperm penetration rate in cattle, sheep and goat oocytes following a comparable pattern; and 3) caffeine depresses the sperm penetration rate in cattle, sheep and goat oocytes, but the pattern of inhibition depends on the genetic origin of the oocytes. The results also suggest that cattle and sheep intact oocytes can be used to assess the fertilizing ability of goat spermatozoa.