Comparative Efficiency of Various Mathematical Functions of Lactation Curve in Gir Cattle using Weekly Milk Yields
B.D. Savaliya S. S. Parikh A. R. Ahlawat R. B. Makwana
Vol 7(5), 112-120
The present investigation was conducted to compare relative efficiency of four lactation curve models in Gir cattle. This study was carried out on 1246 normal lactation records (1-6 parity) pertaining to 357 Gir cows spread over 15 years (2001-2015) maintained at Cattle Breeding Farm, Junagadh Agricultural University, Junagadh (Gujarat). Gamma-type function described the best fit with the highest coefficient of determination (R2=99.82%), whereas, least coefficient of determination (R2 = 85.25%) was observed in Exponential function. Exponential function could not explain initial and peak phase of the lactation, however, it explains only the descending segment of the lactation curve. The trend of Inverse polynomial function (R2=99.76 %), however, indicated that the function might be most suited to cows which start their lactation at very low level of production, reach their peak very early and then start declining at an early stage. Parabolic exponential function (R2=95.00%) indicated wide diversity between actual and predicted yield till the end of the lactation. Gamma-type and Inverse polynomial functions should be preferred over others for predicting milk yield at any stage of lactation in Gir cows. Gamma-type function is recommended for precise fitting of lactation data of Gir cows to help dairy producers use records to achieve efficient breeding and feeding management of dairy herds.
Keywords : Gir Cow Lactation Curve Weekly Milk Yield
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