Water Intake Prediction for Beef Cattle in Brazil

Water is the most important nutrient in animal production. Brazil has the largest commercial cattle herd, where the environmental conditions and beef cattle breeds are distinct from those described in the literature and there is no equation to predict water demanded by beef cattle for Brazilian breeds. Our objective was to validate 6 current water intake (WI) equations for beef cattle using water intake data from three experiments conducted in Southeastern Brazil (Nellore beef cattle). Animal performance, diet composition, and environmental data were collected for all experiments. The prediction of WI using the current published WI equations was tested though the regression between predicted and measured WI values. All tested equations did not agree with the measured WI data from the experiments. WI was overestimated by the previously published WI equations when compared to the actual WI observed in Nellore cattle raised in tropical conditions. Several factors can help to explain why the published equations did not predict the actual WI from the 3 experiments. The tested equations were developed in temperate climates using predominantly Bos taurus taurus. From the current data we generated new WI equations based on metabolic body weight (BW^0.75), dry matter intake (DMI), humidity (HU) and temperature-humidity index (THI) for Nellore cattle in Southeastern Brazil, as follow: – 4.315 + 0.205 × BW^0.75 – 0.17 × HU + 0.913 × DMI + 0.247 × THI. We recommended the proposed equation to estimate WI by Nellore cattle in tropical conditions.