Estimation of Genetic Parameters of First Lactation and Herd Life Traits by Different Animal Models in Murrah Buffaloes
In order to compare different animal models, the methodology of mixed models under animal models was used to predict (Co) variance components of 8 traits related to production, reproduction and life time traits of 1 312 Murrah buffaloes descendent from 122 Sires and 341 dams raised at four military dairy farm viz. Ambala, Agra, Lucknow and Bareilly.The least square means (LSD) of body weight at first calving, age at first calving, first dry period, first calving interval, first service period first lactation milk yield, herd life milk yield, and first lactation period were 503.73±2.68 kg, 1 268.39±15.32 days, 173.01±5.18 days, 467.74±7.42 days, 171.37±7.04 days, 1 702.44±31.015 kg, 5 459.97±76.21 kg, 296.30±3.95 days respectively under model 2 and 501.72±2.58 kg, 1281.33±11.89 days, 173.38±4.49 days, 468.39±6.12 days, 171.74±5.89 days, 1 709.04±25.04 kg, 5 457.49±65.01 kg, 296.74±3.17 days respectively under model 8.The least squares means estimated by model 8 were slightly higher than the means estimated by model 2.The sire had accounted more variation under model 8 than model 2 for body weight at first calving. Since all the traits were analyzed simultaneously under model 2, therefore, there may be some confounding among traits which decreased sire contribution in total variation with body weight at first calving. But that was not the case with model 8 as all the traits were analyzed separately.Additive (direct), environmental and phenotypic variances estimated from univariate and multivariate animal models agreed closely for all the traits. Similarly variance estimated from model 2 and model 8 analyses agreed for environmental and phenotypic variance for all eight traits. Model 2 had slightly higher additive genetic variance for FLP, FDP, FCI and FSP but lower for WFC, AFC, FLMY and HLMY, than model 8. Univariate animal model had slightly lower additive (direct) variance for WFC and AFC than the values estimated under multivariate animal model. Higher additive covariance was estimated between WFC and HLMY followed by FLMY, whereas negative covariance was estimated between WFC and AFC. FLMY had higher additive covariance with HLMY. Additive covariance between AFC and HLMY was higher followed by FLMY.Model 2 had higher h2 estimates among all the four methods employed for all traits, except WFC, and FLMY. The heritabilities estimates under univariate are generally lower than estimates of model 8, except for WFC and HLMY. Higher h2 estimates for AFC, FLP, FDP, FCI, FSP and FLMY, under model 8 were observed than the univaritate animal model. Estimates of heritabilities for FDP and HLMY from multivariate analysis were almost similar to h2 estimates of univariate but slightly lower for WFC and FLMY. The genetic and phenotypic correlations among all first lactation and life time performance traits ranged from very low to very high. FLMY had positive genetic and phenotypic correlations with LTMY.Genetic correlations among different traits ranged from very low to very high under model 2. Phenotypic and environmental correlations also showed same trend.
