Genetic variation among six strains of Romneys and Border Leicester and Coopworth crosses

R.L. Baker, J.N. Clarke; H.H. Meyer; T.G. Harvey and M.L. Bigham.

Ruakura Animal Research Station Ministry of Agriculture and Fisheries, Hamilton; Department of Animal Science Oregon State University, Corvallis, U.S.A.; Rotomahana Research Station Ministry of Agriculture and Fisheries, Rotorua and Whatawhata Hill Country Research Station Ministry of Agriculture and Fisheries, Hamilton

Proceedings of the New Zealand Society of Animal Production. 1987, 47: 101-105

Data collected on the first cross females born between 1979 and 1983 and lambing between 1981 and 1985 are summarised in this paper. Analyses of ewe hogget performance (growth, wool production and oestrous activity) revealed relatively minor variation among the 6 Romney strains, with the exception of greater oestrous activity in RHF-sired hoggets. Coopworth and Border Leicester crosses were heavier, had higher fleece weights and showed more oestrous activity than straightbred Romneys.

Highest reproductive performance was obtained from Coopworth and Border Leicester crosses reflecting breed differences, positive heterosis and heavier ewe body weights. Among the 6 Romney strains greatest variation in reproductive performance was seen for litter size with the RHF-sired ewes excelling and also having the best performance for lambs weaned per ewe joined and lambs weaned per ewe joined as a ratio of ewe body weight. Similarly, the litter size advantage for ewes sired by rams from the 3 Romney group breeding schemes demonstrated that selection for reproductive performance over a period of 10 to 15 years has been successful.

Keywords: NZSAPAB; Sheep; genetic variation; breeds; strains; growth; wool; reproduction