Estimates of some Sources of Variation in the Body Weights of Crossbred Lambs at Different Ages

Abstract

Growth records of 300 fall born lambs were analyzed by the least squares method to determine the effects of breed of dam, birth type, sex, type of rearing and birth weight on weights at 45, 60, 75, 90, 105, 120 and 135 days of age. Differences in lamb weights due to birth type and type of rearing became relatively less important as the lambs grew older. Wethers were heavier than ewe lambs at all ages and the difference at least maintained the same relative importance. Birth weights were the most important source of variation in the lamb weights at different ages and the regression coefficients increased as the lambs grew older. Coefficients of determination (R2) indicated that 29 to 59% of the variation in lamb weights at different ages could be accounted for by the factors studied. These coefficients decreased as the lambs grew older.