Cloprostenol enhances sexual behaviour and semen quality in growing lambs more effectively than Dinoprost

Analogues of PGF2α have been used in boars with positive results on sexual behaviour, but limited impact on semen quality. The objective of this study was to determine whether the administration of Dinoprost tromethamine or D‐Cloprostenol enhances the sexual behaviour and semen quality of sexually inexperienced growing lambs during the onset of the breeding season. The study lasted 10 weeks, beginning during the non‐breeding season, with 24 sexually inexperienced Katahdin lambs (5.1 ± 0.5 months old). Three groups of eight lambs each received: (1) vehicle treatment (group CON); (2) 10 mg of Dinoprost tromethamine (group DIN); or (3) 0.15 mg of Cloprostenol dextrogy (group CLOP). The treatments were all applied im 5 min before the tests of sexual behaviour, or 20 min before the collection of semen. Sexual behaviour was evaluated twice weekly in a pen test with a non‐oestrous ewe, and semen was collected once weekly with an artificial vagina. The latency to begin courtship was significantly shorter in both groups that received analogues of PGF2α than in CON lambs. The number of ano‐genital sniffs, flehmens and lateral approaches was greater in both treated groups than in CON lambs (p