Fitting Various Growth Equations to the Daily Milk Yield Data of Nili-Ravi Buffaloes and Cholistani Cows at Intake at Maintenance Levels.

This study described the daily MY in buffalo and cow under restricted feeding conditions using the five growth models (Brody, Von Bertalanffy, Logistic, Gompertz and Wood). In addition, the species-wise differences in lactation parameters were also tested. These models were fitted to the lactation data of four whole lactations (two buffaloes and two cows) using 1200 unadjusted MY records. Fitting of the model was evaluated through appropriate fitness indicators such as the adjusted R2, Akaike's Information Criterion (AIC), Bayesian Information Criterion (BIC) and Root Means Squared Error (RMSE). The Wood's model provided the best fit of the lactation curves with logical values of parameter estimates owing to higher R2 and lower AIC, BIC and RMSE than other equations. The Wood's model had a better fit of lactation data of cows than of buffaloes. The average estimated values for the initial MY (a), ascending phase before peak MY (b) and descending phase after peak MY (c) were 4.75, 0.238 and 0.004, and 2.56, 0.321 and 0.006 kg/day for buffaloes and cows, respectively. The magnitude of lactation parameters remained higher (P<0.05) in buffaloes for a, peak MY, persistency and lactation yield than in cows. The Woods' model fairly accurately described the lactation data than other equations under restricted feeding conditions, with poor fitting in buffaloes to moderate fitting in cows. [ABSTRACT FROM AUTHOR]