Data consisting of records from 3 040 animals, born of 59 sires and 597 dams, were collected from 1978 to 1991 and analysed to estimate variance components for birth weight, weaning weight, average daily gain (ADG) and Kleiber ratio. Birth year, age of dam, sex and rearing status (a combination of birth and weaning status) were included in the analysis as fixed effects. Methods employed were Henderson`s Method 3, fitting a sire model, and Restricted Maximum Likelihood, using a derivative-free algorithm and fitting four different animal models. The following ranges of heritabilities were obtained from the different models: 0.162-0.327 for birth weight; 0.162-0.350 for weaning weight; 0.176-0.257 for ADG; and 0.130-0.231 for Kleiber ratio. Estimates from animal models which excluded maternal genetic effects were biased upwards, while the inclusion of maternal genetic effects resulted in lower and presumably more realistic variance compoÂ¬nents. Maternal effects were large for birth weight and small for the other three traits. Selection for weaning weight or averÂ¬age daily gain is suggested.