A study of some factors affecting reproductive performance in New Zealand Romney and Border Leicester X Romney two-tooth ewes : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Animal Science at Massey University

Abstract

The reproductive performance of tho ewe is a key factor determining flock productivity and also the rate of genetic improvement possible within flocks. The lambing percentage of Romney sheep in New Zealand is variable but generally unsatisfactory. Crossbreeding with Border Leicesters may provide a method of rapidly improving lamb production. Extensive comparisons of Romney and Border Leicester X Romney (BLX) sheep have been conducted at Whatawhata Hill Country Research Sation (1954 - 1967) and Lincoln College (1952 - 1958). Results were in close agreement. On a per ewe basis, the crossbred was superior to the Romney in growth rate as a lamb and hogget, and in mature bodyweight. In addition, the lambing performance of the crossbred was at least 20 higher, and the growth rate of its lambs about 5% better, than the Romney.