Comparison of Six Different Mathematical Models to the Lactation Curve of Simmental Cows Reared in Kazova State Farm

Abstract

The aim of this study was to investigate the fitness of Incomplete Gamma (WD), Quadratic (Q), Cubic (C), Exponential (WIL), Mixed Log (ML) and Polynomial Regression (AS) models to the lactation curve of Simmental Cows. Data were collected from 752 Simmental cows raised on the Kazova state farm in Turkey. Milk yield was recorded monthly. Total milk yields estimated by the 6 models were very close to real total milk yield. The 6 models were found to be adequate for estimation of milk yield. ML model underestimated the peak yield significantly. The differences between peak yields of the models and real peak yield were statistically insignificant (p > 0.05) and they were ranged from 13.19-18.591. Cubic models forecasted peak time earlier than real peak time. The differences between the persistency values of the 6 models were insignificant (p > 0.05). The 6 model's persistency value was nearly equal to real persistency value. W values of the 6 models changed from 92.69-95.14%. The highest value of R(2) was found in AS model. Furtermore, least value of MSPE was found in AS model. Consequently, the entire model's showed the best fit to the lactation data of Simmental cows and allowed a suitable definition of the lactation curve.