Comparison of four strategies of ram management in a semen collection centre.

Abstract

Thirty Merino rams were used to determine the effect of four management systems of rams on semen quality during the anoestrous season. Animals were divided into four groups: Artificial-Photoperiod group (AP; n=8), which were isolated from females and exposed to artificial long days (16hr/d) from 1 Feb to 15 Mar; Natural-Photoperiod (NP; n=8), isolated from females and exposed to the natural photoperiod throughout the experiment; Oestrous-Ewe group (EE; n=7), housed in a pen adjacent to another pen that housed three ewes in oestrus, and Anestric-Ewe group (AE; n=7), housed adjacent to another pen that housed three ovariectomized ewes. From 20 Mar to the end of May (10weeks), semen samples were collected weekly, and blood samples were collected to determine plasma testosterone concentrations. Mean plasma testosterone concentrations, ejaculate volume and reaction time were not affected either by treatment or week. There was a significant effect (p<.01) of ram treatment on sperm concentration, and both TM y PM, and their interaction, were significantly affected by group and week (p<.001). Rams exposed to ewes in oestrus presented the largest sperm concentration (p<.05) compared with the other three groups, although they had the lowest total and progressive motilities (p<.01). In conclusion, management strategy in spring affects semen quality of rams, with the presence of ewes in oestrus being the best plan to increase sperm concentration.