Effect of restraining rams or change of the stimulus ewe on the libido and semen quality of rams

Abstract

The study utilized 18 Katahdin yearling rams where each ram participated in three experimental sessions spaced 8 days apart. In Treatment 1, the first and second ejaculations of each ram were collected with an AV (artificial vagina). In Treatment 2, rams were used to collect semen as in Treatment 1, but for the second ejaculation a different ewe replaced the original animal used for stimulation. In Treatment 3, rams were used to collect semen as in Treatment 1, but these rams were restrained for 5 min and their reaction time recorded immediately after the first ejaculation. Reaction time to first ejaculation and latency between ejaculations were recorded and both ejaculates evaluated for volume and sperm density. The treatment effects were similar in reaction times and latencies, 73 and 434 s, respectively, for both ejaculations. There was no significant difference among three treatments for semen volume (0.78, 0.69 and 0.89 ml), and sperm number (2.97, 2.86 and 3.73 spermatozoa x 10(9)/ml) for the first ejaculation. Corresponding estimates for the second ejaculation were 0.65, 0.69 and 0.63 ml for semen volume, and 2.97, 2.86 and 3.45 spermatozoa x 10(9)/ml for sperm number. The number of mounts prior to first ejaculation were 2.8, 3.5 and 3.1 for Treatment 1, 2 and 3, respectively (P > 0.05). However, significant differences were detected among treatments in the number of mounts between the first and the second ejaculation (2.5, 3.8 and 1.2). In conclusion, changing the stimulus female for a second ejaculation had no effect on the semen characteristics or the inter-ejaculation interval. However, this increased the number of mounts needed to achieve a second ejaculation, while preventing physical contact with the stimulus animal after the first ejaculation reduced the number of mounts. (C) 2003 Elsevier Science B.V. All rights reserved.