| Abstract: | Eight Merino rams were joined for 8 weeks to 400 Merino ewes in a 31 ha paddock during April–June. Six of the rams were monitored for body weight, body condition, testicular volume and semen characteristics before, during and after the joining period. The day before joining, at 2-weekly intervals through joining, and 2 weeks after the end of the joining period 6 collections were made from each ram using an artificial vagina. The semen was evaluated for volume, density, wave motion and morphology. Body weight and condition and testicular volume of the rams increased prior to joining. Body weight and condition decreased markedly until the sixth week of the mating period, after which there was some recovery. Testicular volume, on the other hand, declined steadily through the mating period and showed no recovery during the post-mating period. Amongst the semen characteristics, ejaculate volume, wave motion score, sperm density and percentage of live sperm all fell significantly during the first 2 weeks of mating but there was a steady recovery through the remainder of the mating period and in the 2 weeks after ram removal. The percentage of abnormal sperm increased significantly throughout the joining period but showed a slight decline in the post-mating period. The results emphasise the extent of the decline in ejaculate characters, and to a lesser extent, in physical characters which can occur during the first cycle of joining in paddock-mated rams. |
