Phenotypic and Genetic Parameters Estimation for Birth Weight in Zebu and Crossbred Calves Born Under Organized Farm Conditions in India

Abstract

Data on birth weight of Zebu (Sahiwal and Tharparkar) and Crossbred (Holstein Friesian X Tharparkar) cattle spread over 16 years were utilized to assess the influence of genetic and environmental factors on calf birth weight, and to estimate variance components and genetic parameters. Non genetic factors taken into consideration were season of birth, period of birth, sex of the calf, dam’s parity and gestation period. Least squares means for birth weights of Sahiwal (S), Tharparkar (TP) and crossbred (CB) cattle was 19.92 ± 0.18, 20.91 ± 0.25 and 28.29 ± 0.29 kg respectively. All the non genetic factors, except period of birth (Sahiwal) and gestation period (Tharparkar), included in the study had a significant effect on birth weight of calves in all the three breeds. Heritability estimate for birth weight by paternal half-sib method on 1520 progeny from 48 sires was 0.149 ± 0.055 in Sahiwal, whereas on 2360 progeny from 101 sires was 0.323 ± 0.063 in crossbred. Variance components and genetic parameters due to direct additive genetic and maternal additive genetic effects were estimated by using two univariate animal models (Model 1 and 2) using AIREML algorithm of WOMBAT software. Model 1 produced highest estimate of additive genetic variance (3.65 Kg², 3.90 Kg² and 15.38 Kg² for Sahiwal, Tharparkar and crossbred respectively) and direct heritability (0.57, 0.60 and 0.67 for Sahiwal, Tharparkar and crossbred respectively) in all the three breeds. When maternal influence was included in the Model 2, the direct heritability (h²_d) estimate were 0.14, 0.55 and 0.34 and the maternal heritability (h²_m) estimate for birth weight were 0.19, 0.16 and 0.13 in Sahiwal, Tharparkar and crossbred respectively. Model 2 was better in estimation of variance components of birth weight for all three breeds because of significant improvement in likelihood value.