The purpose of this study was to estimate the variance components and genetic parameters for birth weight in Brown Swiss cattle reared at Malya and Konuklar State Farms, Türkiye. The least square means of birth weight were 39.91±0.005 and 42.26±0.09kg for the calves raised at Malya and Konuklar State Farms, respectively. The effects of calving year, parity and calf sex on birth weight were significant (P<0.05). The effect of calving season on birth weight was highly significant (P<0.01) for Malya State Farm, while it was non-significant for Konuklar State Farm. Direct heritability (h²_d), maternal heritability (h²_m), total heritability (h²_T) and the fraction of variance due to maternal permanent environmental effects (c²) were 0.09, 0.04, 0.11 and 0.04, respectively for birth weights of the calves raised at Malya State Farms. The corresponding values of birth weight for calves raised at Konuklar State Farm were 0.39, 0.015, 0.29 and 0.018, respectively.

Key words: Birth weight; Brown Swiss calf; Heritability; Maternal effect; Repeatability; Variance component