EFFECT OF INDOLE-3-ACETIC-ACID (PLANT AUXIN) ON BOAR SPERM MOTILITY AND PREGNANCY AND PROLIFICACY RATES AFTER FREEZING AND THAWING

The effects of the plant auxin, indole-3-acetic acid (IAA), introduced either immediately before freezing and/or at thawing of boar semen we re studied in vitro and in vivo. In vitro, IAA significantly slowed do wn the decreases in motility and in the percentage of motile spermatoz oa over a 2 h incubation at 39 degrees C. This effect was observed wit h 100 ng/ml IAA(5.7 x 10(-7) M) but not with 10 ng/ml IAA (5.7 x 10(-8 ) M). Moreover, a positive effect of 100 ng/ml IAA on acrosome integri ty was evidenced whatever the moment of introduction of IAA. In vivo, no effect could be demonstrated on the pregnancy rate of sows in the p resence of IAA but a significant increase (p < 0.05) in prolificacy (e mbryo survival) was observed when IAA (100 ng/ml) was added either bef ore freezing (10.1 +/- 2.8) or at thawing (9.3 +/- 2.7) when compared to controls (7.4 +/- 3.5) (n = 27 per group). It is speculated that au xin increases the scavenging of reactive oxygen species (O-2(-.), H2O2 ) produced upon freezing and thawing of sperm by stimulating protein d isulfide isomerase (PDI) that would in turn protect the sperm membrane proteins from denaturation.