Effect of parity on the shape of lactation curves in purebred Jersey cows in Indian conditions

ABSTRACT

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.

KEYWORDS:

• Dairy cows
• non-linear modeling
• lactation
• parity
• persistency

Acknowledgments

The authors are very grateful to the Commissioner and Joint Commissioner, Department of Animal Husbandry, Dairying and Fisheries, Ministry of Agriculture and Farmers Welfare, Government of India for permission to compile data from Central Cattle Breeding Farm, Sunabeda, Koraput, Odisha, India. We also thank the Director of the Indian Veterinary Research Institute for providing the necessary facilities for this research.

Disclosure statement

No potential conflict of interest was reported by the authors.