Effect of Cold Shock on Boar Sperm Treated with Butylated Hydroxytoluene

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Abstract
In 3 experiments boar sperm were treated with butylated hydroxytoluene (BHT) and subsequently cold shocked at 0°C for 10 min. The effects of cold shock on acrosome morphology, sperm motility and fertilizing capacity were assessed. In experiment 1 the concentrations of BHT tested were 0, 0.1, 0.5, 1 and 2 mM. The percentages of acrosomes with a normal apical ridge (NAR) and of motile sperm after cold shock were higher for sperm treated with 0.5, 1 or 2 mM BHT than for unrtreated sperm (P<0.01 for each comparison). In experiment 2 the cold shock protection provided by 2 mM BHT was compared with that of the Beltsville F5 (BF5) extender containing egg yolk lipoprotein and the Beltsville F3 (BF3) extender containing casein. The percentage of NAR acrosomes after cold shock was significantly higher for sperm treated with BHT than for sperm extended in BF5 or BF3. When sperm were treated with BHT and then extended with BF5 or BF3, the percentage of NAR acrosomes after cold shock was significantly lower than if sperm were treated only with BHT. In experiment 3 sperm that were treated with 2 mM BHT retained their fertilizing capacity during cold shock while unprotected control sperm lost their fertilizing capacity during cold shock. These experiments provided conclusive evidence that BHT protects the morphological and functional integrity of the sperm membranes against cold shock damage to the extent that boar sperm were capable of fertilizing ova.