I. Effects of number of ewes joined per ram, age of ewe, and paddock size

Abstract

In two experiments groups of three rams were joined with 100, 200, or 300 ewes either in small flat paddocks or in extensive hill paddocks. Mating groups comprised equal numbers of two-tooth and mixed age (older) ewes. Mean live weights at the start of mating were 35.0 and 41.5 kg for two-tooths in Experiments 1 and 2 respectively, and mixed-age ewes were 45.0 kg in both experiments. In both experiments ewe fertility was high when three rams were joined with 100 ewes. Increasing the number of ewes (3/100 to 3/300) per ram in Experiment 1 resulted in fewer ewes mated in the first 17 days of mating, a reduction in the mean number of rams mating each ewe, and an increase in barrenness. These effects were greater in two-tooth ewes. In Experiment 2 effects were similar in two-tooths but smaller in magnitude, and the reproductive performance of mixed-age ewes was relatively unaffected by the number of ewes per ram. Although paddock size had little effect on the percentage of ewes mated, ewes joined with rams in large mating paddocks were mated by fewer rams. Shape and topography of a mating paddock seem to be more important than area. Percentage of ewes lambing to mating by one ram only was lower than in ewes mated by two or three rams. Providing two-tooth ewes were mated, their fertility was comparable with that recorded in mixed-age ewes. However, twinning was lower in two-tooths than in mixed-age ewes.