Testing the efficacy of different lactation curve models for monthly test day milk yield
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Authors
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BIJENDRA NARAYAN SHAHI
G B P U A & T, Pantnagar
Keywords:
Lactation curve, Test day yield, Exponential function, Parabolic exponential function, Inverse polynomial function, Gamma type functionAbstract
The test day milk yield data on 511 crossbred cattle were obtained and utilized according to monthly interval upto 305th day maintained at Instructional Dairy Farm, of G. B. Pant University of Agriculture and Technology, Pantnagar (Uttarakhand). The different statistical models considered in this study for predicting the shape of lactation curve were Exponential Function, Parabolic Exponential Function, Inverse Polynomial Function and Gamma Type Function. Maximum  coefficient of determination (R2) value was observed for Inverse Polynomial function (R2 = 99.97%) followed by Gamma function (R2 = 88.28%), Parabolic function (R2 = 80.95 %), and Exponential function (R2 = 39.10%). The root mean square error (RMSE) was least for Inverse Polynomial function (0.07 kg) followed by Gamma Type function (0.10kg ), Parabolic Exponential  function (0.12 kg ) and Exponential function (0.21 kg ). The absolute mean deviation (AMD) was least for Inverse Polynomial (0.16 Kg) followed by Gamma Type function (0.24 Kg), Parabolic Exponential (0.31Kg) and Exponential function (0.48) confirming the same order of superiority.
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