Effects of different stocking intensities in early life on the productivity of Merino ewes grazed as adults at two stocking rates. 2. Reproductive performance

Abstract

The reproductive performance of ewes subjected to four nutritional regimes from conception to 15 months of age was recorded from first lambing at 24 months until the seventh lambing. The ewes were grazed at 10 and 20 sheep/ha. The proportion of ewes which exhibited oestrus at their first mating was less in those which had grazed at a high stocking rate between 3 and 15 months, and fecundity was increased by 15% in subsequent years by a high plane of nutrition between conception and 3 months of age, but only when ewes were grazed at a low stocking rate as adults. Ewes stocked at 10 sheep/ha weaned 50% more lambs than ewes stocked at 20 sheep/ha in adult life, but the more heavily stocked ewes weaned approximately 33% more lambs on a unit area basis. Approximately half the variability in the number of lambs weaned per ewe available for service was associated with variability in lamb survival. Relationships between the proportion of ewes showing oestrus, fecundity, survival of lambs, overall reproductive performance and liveweight of ewes are presented.