Water Disappearance and Manure Production at Growing-Finishing Commercial Pig Farms in Brazil-A Simplified Model Approach

The aim of this study was to fit water disappearance and manure production curves at growing-finishing commercial pig farms and compare the curve that best describes the evolution of parameters evaluated, according to three variables: age, body weight, and pigs' housing period. Accordingly, 33 production cycles were evaluated considering a housing period of 105 days (13,276 pigs-nine weeks old and 24.5 kg average body weight) during 13 months in 15 commercial pig farms located in southern Brazil. The variables analyzed were used to adjust the water disappearance and manure production curves (Brody, Gompertz, Logistic, Richards, and Von Bertalanffy) and to estimate its biological parameters according to the NLMIXED SAS procedures. It was found that the Logistic model was the one that best described both the water disappearance and the manure production, displaying an asymptotic adjustment and estimated values measured in farms, e.g., pigs age (water: R-2 = 0.989, absolute error: 1.11 L/pig/day, and prediction error = 1.32%; manure: R-2 = 0.995, absolute error = 0.04 L/pig/day, and prediction error = 0.96%). It is emphasized that the models determined in this research are the basis of the development of an instantaneous measuring device that allows the producer to visualize both the water disappearance (plotting the daily measures) as well as manure production in the farm and compare the values with the estimated curves.