Comparison of standard lactation curve models using fortnightly milk records in Frieswal cattle

Abstract

Aim: The aim was to compare standard lactation curve models using fortnightly milk records in Frieswal cattle. Materials and Methods: A total of 2904 fortnightly milk yield (FMY) records from 132 Frieswal cattle maintained at Military Farm, Bareilly, Uttar Pradesh were taken for study. The Wood (WD), Morant and Gnanasakthy (MG), Mitscherlich x Exponential (ME), and Wilmink (WK) models were fitted on average FMY (AFMY) by nonlinear regression using statistical package SAS 9.3 version. The goodness of fit of models was judged by the adjusted coefficient of determination (Adj. R2) and root mean square error. Results: The AFMY ranges from 127.09 kg (first fortnight) to 110.04 kg (last fortnight) with peak fortnight yield of 189.51 kg and peak period at fourth fortnight. Predicted peak yield by different models ranges from 182.7 to 190.2 kg. The herd average milk yield was predicted with a high degree of accuracy (Adj. R2>92%) by all models with the maximum accuracy (Adj. R2=99.20%) obtained by ME model followed by MG (Adj. R2=98.8%) and WK model (Adj. R2=96.0%). Conclusion: The ME model provided best fit for FMY data in Frieswal cattle followed by WK and MG model, whereas WD model fitted least.