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Prediction of water intake and excretion flows in dairy cows under thermoneutral conditions

Prédiction des flux d'eau consommée et excrétée par les vaches laitières en conditions de thermoneutralité

Abstract : The increase in worldwide demand for dairy products associated with global warming emphasizes theneed for a higher efficiency of water use in dairy systems. In this study, equations were developed to predict the main water flows at the dairy cow level, based on parameters related to cow productive performance and diet under thermoneutral conditions. A dataset including 342 individual measurements of water balance in dairy cows at the experimental farm of Méjussaume (INRA, France) was built. Predictive equations of water intake, urine and fecal water excretions were developed by multiple regression using a stepwise selective of candidate regressors.While dry matter intake (DMI) was the first predictor of total water intake with a partial R² of 0. 51, diet dry matter content (DM) was the first predictive parameter of fresh water intake with a partial R² of 0. 57, likely due to the large variability of DM in the first dataset (from 11, 5 to 91, 4%). This confirmed the compensation between water drunk and ingested with the diet when DM changes. The variability of urine volume was explained mainly by the amount of crude protein ingested with forage (qtCPf) associated with DMI and that of fecal water was explained by the percentage of concentrate in diet and DMI.