Mating Behavior of the Ram in the One-Sire Pen

Abstract

Thirty-two breeding pens containing one ram and 18 to 38 ewes each were observed continuously for 7-day periods for mating and related activity in late fall at Dubois, Idaho. Variation in air temperature, wind velocity, cloud cover, precipiation, brightness of moonlight, type of artifical light at night (sealed beam spotlight or infrared illumination), age, inbreeding, body weight, semen score and previous use had no important influence on mating behavior. Rambouillet rams appeared to be more active than either Targhee or Columbia rams. Targhees were intermediate between the other two breeds. The number of ewes in heat and individual ram differences independent of number of ewes in heat were the two most important factors affecting mating behavior in the ram. The most active ram mated 66 times in 6 days during which one or more ewes were in heat 73% of the time, as compared with 18 times for the least active ram with one or more ewes in heat 87% of the time. The average ram mated 45 times in 6 days (standard deviations=17) during which one or more ewes were in heat 70% of the time. The number of times each ewe was mated after an initial drop in the number of matings per ewe tended to remain fairly constant regardless of the number of ewes in heat. Thus, an increase in number of ewes in heat resulted in a marked increase in the number of matinges per ram per day. The number of mounts per mating was unaffected by the number of ewes in heat. Seeking time per hour was little different with one, two or three ewes in heat, but was greater when no ewes were in heat. The rams spent slightly less time lying down and eating as the number of ewes in heat increased from none to three. The time between first and second ejaculates during semen testing was not significantly correlated with number of matings per hour. However, the number of mounts per ejaculate in semen tests was significantly related to number of mounts per mating in actual service. The rams which required the fewest mounts per mating mated the most ewes on the average. Rams were more active for several hours immediately after introduction into breeding pens than later. Stimuli such as initial introduction into breeding, number of ewes in heat, feeding time and the need for a rather definite amount of rest unbothered by daylight disturbances had greater influence on mating behavior than hour of day or amount of light. None of the mating behavior characteristics of the ram studied were significantly correlated with percent of ewes lambing.