Effects of visual stimuli or change of the stimulus ewe on libido and semen characteristics of crossbred rams during breeding season

Abstract

The main purpose of this study was to determine the effects of visual stimuli or change of the stimulus ewe on libido and semen characteristics of crossbred rams during breeding season. In experiment 1: four 3-year-old Arkharmerino×Ghezel rams and eight 3-year-old ewes were exposed to different sexual stimulation procedures. In the first procedure, the same ewe was used as the female stimulus for three consecutive presentations, but in the second procedure the stimulus ewe was replaced after the second presentation by a new female. In experiment 2: twenty mature crossbred rams consisting of Baluchi×Moghani, Ghezel×Baluchi, Arkharmerino×Ghezel and Arkharmerino×Moghani were used in this study. Animals were randomly allocated into two equal groups. In the first group, the rams were affected by visual stimuli (VS), while in the second group, rams were depriving of visual stimuli (NVS). Reaction time, semen volume, sperm concentration, forward progressive motility, live sperm and sperm abnormality rates were scored. In rams treated with change of the stimulus ewe a decrease in semen volume and sperm concentration in the successive ejaculations was observed, being highly marked in the third ejaculation independent of the stimulation procedure (1.09 vs. 0.81 and 0.85 mL, and 2.91 vs. 2.14 and 2.15 x 1012/mL to the first and third ejaculation respectively; P<0.05). The most significant differences were observed in either forward progressive motility (70.73 vs. 69.31 and 82.3 %), live sperm (70.84 vs. 72.37 and 82.5 %) and sperm abnormalities rates (10.73 vs. 9.91 and 6.7 %) in the first and third ejaculation, respectively (P<0.05). Libido and mounting behavior variables were substantially decreased in reaction time in the third service when the ewe was changed. However, for rams treated with visual stimuli, only the semen volume increased (0.84 vs.1.03 mL, P<0.05). No significant differences were observed either in reaction time, mating behavior, sperm concentration; forward progressive motility, live sperm and sperm abnormality rates. These findings suggest that visual stimulus or change of the stimulus ewe increased sexual potency in breeding and semen output of crossbred rams.