Genetic studies on prediction of lactation yield based on test day values in Sahiwal and crossbred cattle
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Date
2017-06
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
The present investigation was carried out for studying the different fortnightly test day milk yield traits, first lactation milk yield traits, prediction of first lactation yield on the basis of single test day milk yield and stepwise backward elimination method and comparing the different sire evaluation methods. The records of 799 daughters of 58 sires in crossbred cattle and 166 daughters of 19 sires in Sahiwal cattle maintained at Instructional Dairy Farm, G.B.P.U.A& T, Pantnagar were utilized for this study.
The least squares means along with standard errors of AFC, FL305DMY, FLL, FLPY and fortnightly test day milk yield (FTDY-1 to FTDY-21) traits were observed as 1445.34±30.77 days, 1716.04±78.47 kg, 248.45±9.84 days, 8.84±0.15 kg and 4.29±0.5, 5.34±0.7, 7.71±0.6, 7.63±0.8, 7.45 ±0.10, 7.11±0.90, 7.08±0.10, 6.87±0.75, 6.34±0.08, 6.34±0.08, 6.12±0.64, 6.34±0.12, 5.96±0.54, 5.65±0.12, 5.28±0.10, 4.74±0.10, 4.24±0.11, 3.49±0.84, 3.28±0.07, 2.93±0.47, 2.73±0.03 and 2.50±0.03 kg respectively, in Sahiwal cattle. The corresponding figures for crossbred cattle were observed as 1376.15±24.19 days, 2657.69±63.18 kg, 283.93±4.94 days and 13.18 kg. 4.48± 0.13, 5.6±0.2, 9.53±0.48, 9.35±0.6, 8.7±0.45, 8.6±0.6, 8.35±0.08, 7.83±0.3, 7.6±0.7, 7.11±0.08, 6.56±0.45, 6.08±0.32, 5.71±0.8, 5.27±0.21, 5.26±0.18, 4.98±0.78, 5.13±0.21, 4.51±0.74, 5.03±0.11, 4.75±0.02 and 4.49±0.81 kg respectively. The heritability estimates of AFC, FL305DMY, FLL and FLPY traits in case of Sahiwal and crossbred cattle indicated that some improvement can be made in these traits by selecting the cows for these traits up to some extent. However, the major improvement in these traits can be done by good managemental practices at the farm.
The heritability estimates for early test day milk records were lower in magnitude and later in the middle of lactation, the values were found to be comparatively higher in magnitude. All the genetic and phenotypic correlations between FL305DMY and different test day milk yield found to be positive in direction. The genetic and phenotypic correlations among test day milk yield revealed that the data on test day milk yields can be utilized for extending the incomplete records and also utilized under various selection programmes. The step wise regression was best fitted for predicting the FL305DMY followed by regression and ratio method. The fitting of step wise multiple regressions, the higher estimates of accuracy of prediction for FL305DMY were found in the middle part of the lactation (FTDY8 to FTDY-10 in Sahiwal and FTDY-7 to FTDY-11 in crossbred cattle). The multiple regression equations with six variables viz. peak yield, FTDY-2, FTDY-6, FTDY-8, FTDY-10 and FTDY-15 in case of crossbred cattle and peak yield, FTDY-2, FTDY-3, FTDY-6, FTDY-10, and FTDY-11 in case of Sahiwal were considered more appropriate for prediction of first lactation 305 day milk yield with high accuracy. The BLUP method was found to be superior for selecting the sires for first lactation milk yield followed by LSM and Simple daughter average method.
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