EFFECT OF INDOLE-3-ACETIC-ACID (PLANT AUXIN) ON THE PRESERVATION AT 15-DEGREES-C OF BOAR SEMEN FOR ARTIFICIAL-INSEMINATION

In order to extend the duration of boar sperm survival at 15 degrees C for artificial insemination, we tested the effect of indole-3-acetic acid (IAA), which appeared to be the main sperm protective substance p resent in the Coco nucifera endosperm (coconut water). Two IAA concent rations (10 and 100 ng/mL) in Beltsville extender (BTS) were studied f or their in vitro effects. The motility, the percentage of motile sper matozoa and the acrosome morphology of sperm were recorded each day ov er 13 days of storage at 15 degrees C, after 5 min and 3 h of incubati on at 39 degrees C. The IAA effect on sperm preservation was also stud ied in vivo at a concentration of 10 ng/mL in BTS by inseminating grou ps of females twice at 24 h intervals either at DO (day of sperm colle ction) and D1 (D0/1) or at D5 and D6 (D5/6). At D0/1, the two groups o f females (control and IAA) were inseminated with a total of 6.3 x 10( 9) spermatozoa (3.15 x 10(9) at DO and the same dose at Dl)whereas at D5/6, one IAA group was inseminated with a total of 6.3 x 10(9) sperma tozoa and another one with 12.6 x 10(9) spermatozoa. The animals in th e D5/6 control group were inseminated each with a total of 12.6 x 10(9 ) spermatozoa. For each group of females (n = 106-140), fertility rate (% farrowing) and prolificacy rate (litter size) were recorded. No ef fect of IAA in vitro on the motility rate and on the percentage of mot ile spermatozoa was observed over a 13 day storage. However, IAA (10 n g/mL) had a significant positive effect on the percentage of living sp ermatozoa with intact acrosomes after 13 days (66 vs 54%, P < 0.05). T he fertility and prolificacy rates after 5-6 days of sperm preservatio n in BTS extender alone did not differ significantly between D5/6 and D0/1 but the total number of inseminated spermatozoa was 12.6 x 10(9) at D5/6 instead of 6.3 x 10(9) at D0/1. When the spermatozoa were stor ed in the presence of 10 ng/mL IAA for 5-6 days at 15 degrees C, the f ertility and prolificacy of the females inseminated with only 6.3 x 10 (9) spermatozoa were identical to those of the females inseminated wit h an equal number of spermatozoa at D0/1 in the presence or absence of IAA.