Lambing potential and mortality in Merino sheep as ascertained by ultrasonography

Abstract

The results of commercial ultrasongraphic determination of fetal number in 47 648 autumn-joined and 7846 spring-joined Merino ewes on private properties in New South Wales were analysed to determine reproductive potential. Overall, about 12% of maiden ewes and 31% of adult ewes were diagnosed as carrying twins, with about 5% of ewes diagnosed as dry. Season of joining had no effect on these proportions, except for a slightly lower number of dry ewes among those spring-joined. This analysis indicates that the average flock gives birth to 121 lambs per 100 ewes joined, while the average number of lambs marked per 100 ewes is 80. This means that the State flock is achieving only two-thirds of its potential.