A NOTE ON THE INFLUENCE OF ADDED RELAXIN ON THE FERTILITY OF AGED BOARD SEMEN

Two experiments were performed to evaluate the influence of relaxin on the fertility of gilts inseminated with aged boar semen. For experime nt 1, oestrus was induced in 43 Yorkshire X Landrace gilts by injectio n of 400 i.u. PMSG plus 200 i.u. hCG. At 24 h after oestrus detection, gilts were inseminated with fresh semen (1 to 2 day old; no. = 15), a ged semen (5 to 6 days old; no. = 15) or aged semen containing 400 mug /l of relaxin added at the time of semen extension (no. = 13). Pregnan cy rates 24 days after insemination were lower in gilts receiving aged semen (P < 0.05), an effect not prevented by added relaxin. There was no effect of either semen age or relaxin on numbers of embryos. In ex periment 2, the ejaculates of eight boars were extended with or withou t the addition of 400 mug/l relaxin and motility monitored for 7 days. Fresh sperm motility decreased from 87-5 (s.e. 2.5)% at collection to 71.2 (s.e. 3.3)% after 7 days. The attenuation of sperm motility was not affected by relaxin.