Sperm output by rams and distribution amongst ewes under conditions of continual mating

Variables associated with mating in rams were compared before and after continuous mating for 6 days. The effect of behaviour and sperm output of individual rams on the number of spermatozoa received by each ewe was measured. Spermatozoa were collected by an intravaginal device which is described and validated. Fourteen rams, isolated from ewes for at least 2 months previously, were each allowed to mate continually with 4 fresh oestrous ewes on each day for 6 days. The number of spermatozoa per ejaculate fell from 3900 +/- 908 x 10(6) to 77 +/- 39 x 10(6). In 8 rams the number of ejaculates per 24 h fell from 17.25 +/- 2.5 to 11.5 +/- 1.5. Five of these 8 rams were then mated with 1, 4 or 8 ewes during each of the next 3 days. At all times rams preferred certain ewes and no more than 5 ewes were mated per day by each ram regardless of the number available. The mean number of ejaculates per ewe varied from 0 to 12.1 for continuously worked rams and from 0.3 to 10.5 for fresh rams. There were 7.0 +/- 1.8, 11.5 +/- 1.5 and 12.1 +/- 1.1 ejaculates/day in the presence of 1, 4 and 8 oestrous ewes, respectively.