Genetic aspects of cold resistance in new-born lambs

J.E. Wolff, R.L. Baker, P.M. Dobbie, A.J. Ford, R.B. Jordan

Ruakura Animal Research Station, Ministry of Agriculture and Fisheries, Hamilton

Proceedings of the New Zealand Society of Animal Production. 1987, 47: 93-98

The cold resistance (CR) of 468 new-born lambs was measured by immersion of lambs in a progressively cooling water bath. The ability to withstand cold (CR time) was defined as the time taken from the start of water cooling until the lamb's rectal temperature reached 35°C. The lambs were sired by seven different breeds with Romney, Perendale or Booroola Merino-cross dams. Both the lamb's liveweight prior to immersion in the water bath and its wool depth were positively correlated with CR time. After adjusting CR time for lamb weight, wool depth and other known environmental effects (year of birth, sex, birth rank and age of dam), there were no significant differences among sire breeds or dam breeds. Paternal half-sib heritability estimates of cold resistance were 0.36 ą 0.16 (ignoring lamb weight and wool depth) and 0.44 ą 0.18 (adjusting for lamb weight and wool depth). The findings support the concept of a genetic influence on cold resistance in the new-born lamb.

Keywords: NZSAPAB; Mortality; hypothermia; temperature regulation; cold resistance; heritability; breed; lambs; sheep

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