The effects of undernutrition on libido and semen quality in adult Merino rams

Abstract

Groups of mature Merino rams were fed at maintenance, or at 75 or 50% of maintenance, for a 15-week experimental period, during which the treated groups lost on average 12.5 and 20.6% of their respective initial body weights. Libido and semen quality were assessed at weekly intervals on a series of eight ejaculates collected from each ram at 20-min intervals. Libido, as assessed by reaction time, number of mounts per ejaculate, frequency of failure to ejaculate, and vigour of the ejaculatory thrust, was progressively and markedly depressed in both treated groups during the last third of the experiment. Semen quality (volume, density, and motility of ejaculate, and methylene blue reduction time) was significantly greater in the first than in the eighth ejaculate collected each week, and the quality of the first but not the eighth ejaculate was significantly depressed during the last month of the experiment in both treated groups.