Modulation of Postthaw Motility, Survival, Calcium Uptake, and Fertility of Bovine Sperm by Magnesium and Manganese

¹ Centre de Recherche en Biologie de la Reproduction, Département des Sciences Animales, Université Laval, Ste-Foy, QC, Canada G1K 7P4
² Department of Animal and Poultry Science, University of Guelph, Guelph, ON, Canada N1G 2W1

Because Mg²⁺ and Mn²⁺ are potent stimulators of motility through the stimulation of adenylate cyclase activity, the current study was undertaken to modulate the fertilizing ability of bovine semen by incorporation of various concentrations of those two salts in extenders before freezing. Motility analysis at 6 h in vitro showed a positive effect of MgCl₂ in a dose-dependent manner from 0.5 to 5 mM (31 to 50%). Manganese at the concentration of 0.1 mM also supported good sperm motility (53%) compared with that of the control (28%). Although survival was increased, no detrimental effects were seen on the number of sperm that penetrated mucus of cows in estrus. The intracellular Ca²⁺ concentration of sperm was very different across treatments after thawing; spermatozoa that were extended with 2 mM MgCl₂ and 0.5 mM MnCl₂ possessed the highest concentrations at thawing. Four hours later, in the presence of Ca, spermatozoa that were extended in 0.1 mM MnCl₂ showed the highest uptake. In the presence of Ca and heparin, spermatozoa that were extended in different amounts of Mg showed Ca²⁺ concentrations that increased in a dose-dependent manner. This effect was negated by glucose. Functional fertilizing capacity was also evaluated by in vitro fertilization, and the different treatments did not show any detrimental effects. In summary, 5 mM MgCl₂ and 0.1 mM MnCl₂ both have beneficial effects for the maintenance of sperm motility without detrimental effects on mucus penetration and fertilizing ability. Furthermore, these treatments do not prevent subsequent Ca²⁺ uptake in response to heparin. These in vitro studies are potentially a good sorting system to predict the benefits of extender modifications.

Key Words: magnesium • manganese • calcium • semen extender

Submitted on November 1, 1995
Accepted on April 29, 1996