Effect of parity on the shape of lactation curves in purebred Jersey cows in Indian conditions
2022
Mohanty, Barada Shankar | Verma, Med Ram | Sharma, Vijay Bahadur | Patil, Vijay Kumar
A data set of 261 lactations from 130 purebred Jersey cows was fitted using six nonlinear lactation curve models viz. Sikka (SIK), Morant and Gnanasakthy (MG), Wilmink (WK), Wood (WD), Guo and Swalve (GS), and Brody (BRD) models. The average weekly test day milk yields (WTDMY) were predicted with high values of adjusted coefficients of determination (R² ₐdⱼ) by all fitted models. The MG model yielded the highest degree of accuracy (R² ₐdⱼ = 94.3%) with the lowest values of root mean square error (0.383), Akaike information criterion (−78.788), corrected Akaike information criterion (−77.735), and Schwartz Bayesian information criterion (−71.743) for the overall study. Among the four parities, the MG model was best fitted for the first three parities; however, for parities greater than or equal to four, the BRD model provided the best fit. All models fitted for overall milk production over four parities showed degrees of accuracy greater than 80. All the estimated peak yields estimated by different models ranged from 86.03 kg to 93.38 kg and the peak period ranged from 5 to 9 weeks. Lactation persistency was measured by the ratio, Weller, and Mahadevan methods. Cows with flatter lactation curves generally exhibited higher lactation persistency.
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