Survey observations on the reproductive performance of both romney stud and commercial flocks throughout New Zealand

Open Access
Publisher Website
Google Scholar
Abstract
Results of a series of surveys during 1965–68 to collect basic data on the reproductive perfonnance of registered Romney stud flocks totalling more than half a million ewes are given. For presentation and analysis of the data, New Zealand was divided into six geographical areas based on latitude: northern (l), central (2), and southern North Island (3)|northern (4), central (5), and southern South Island (6). The following are conclusions from the data:— 1. The percentage of maiden ewes (1.5-year-old) in the six areas respectively was: 22.8, 24.1, 27.3, 25.3, 25.5, 25.0 (P<0.001). 2. The mean incidence of barren ewes in the respective areas was: 7.4%,5.5%,6.4%,6.8%, 5.9%, 5.1 % (P<0.01). 3. The mean total lamb production of the ewes which lambed was 133.5%. The respective averages for the six areas were: 121.9%, 125.8%, 132.9%, 132.4%, 137.8%, 138.4% (P<0.001). Significant between-year differences were also demonstrated: 1965, 131.5%, 1966, 132.9%;1967, 133.3%;1968, 137.7% (P<0.001). Similar between-area and betweenyear differences were also demonstrated in the percentage of lambs tailed to total ewes. 4. Of the ewes which lambed a mean of 8% lost all their lambs. The respective area incidence was: 10.0%, 8.8%, 8.8%, 6.9%, 7.0%, 6.6% (P<0.001). Similarly, there was a linear decrease in lamb deaths during the perinatal period to tailing from north to south: Area 1, 13.7%;2, 12.2%;3, 12.6%;4, 9.2%;5, 10.9%;6, 10.5% (P<0.001). Significant between-year differences were also demonstrated in both the incidence of ewes which lost all lambs and total lamb deaths. 5. The lamb tailing percentage was not well correlated to ewe flock size. The data showed a quadratic rather than a linear fit, and significant correlations were demonstrated only in 1966 in flocks in the following areas: central and southern North Island, southern South Island.

This publication has 3 references indexed in Scilit: