ESTIMATION OF VARIANCE COMPONENTS AND HERITABILITY OF BIRTH WEIGHT THROUGH DIFFERENT METHODS IN SWEDISH RED AND WHITE CATTLE

Data on368birth records of Swedish Red and White cattle herdraised organically atgan Organic Dairy Cattle Farm for a period of 2006 and 200 9(4years) were used to estimate the effects of different environmental factors on birth weight. Additionally, a comparison of four methods for variance component estimation to compute heritability of birth weight was performed using ML (Maximum likelihood), MINQUE (Minimum variance quadratic unbiased estimation), REML (Restricted maximum likelihood) and Hendersons Method III. Average abortion rate, stillbirth rate, twin and single birth rates of S wedish Red and White cattle were as 4.5%, 4.3%, 3.2% and 87.7% respectively. The least square s mean for birth weight was 37.4±0.70 kg. While effects of calving year (P 0.05). Sire and error variance componentsand standard error of the heritability obtained by using ML method were lower than those obtained by the other three methods. Heritability estimates for birth weight obtained by ML, REML, MINQUE and Henderson Method III were 0.57±0.22, 0.62±0.24, 0.65±0.25 and 0.59±0.24, respectively. It is concluded that the ML procedure was superior for estimating variance components and heritability of birth weight of Swedish Red and White c attleand non- genetic factors influencing the birth weight should also be considered in selection and an adjustment for the significant environmental factors should be made.