PSXIII-9 - Is There Any Relationship Between Water Intake and THI in a Brazilian Experimental Feedlot Under Tropical Conditions?

Abstract: Temperature-humidity Index (THI) is an important stress marker. Furthermore, in tropical areas such as Brazil, even zebu cattle might suffer some heat stress. Therefore, for 50 days (summer and fall seasons) in a research feedlot center in southeast of Brazil data were collected regarding THI as well as water intake by INTERGADO water drinker system, that can measure water intake through a wireless technology. This equipment has a scale which measure the water intake. The methods of this trial were by collecting data from 40 Nelore cattle for 50 days. Thereafter, each day was measured the average intake among those animals. The THI was measured following the model purposed by Steadman (1979). Thus, a model was carried out by SAS using GLM as well as ANOVA to predict the best model between these 2 parameters. However, there was not any significance between those 2 parameters. The best slope was a cubic model. The R2 of this slope was only 0.016. The equation had been, Water Intake= 368.77xTHI+5.27*THI2- 0.025xTHI3+ 8618.53 (n=50). Although, there are evidence that THI may impact animal stress and performance. THI seems not to be a good predictor related to Water Intake. One of the reasons for this must be the THI average throughout this experiment =70.3 ± 5.36 and water intake average = 27.92 ±5.66. Whereas some authors, recommend only alert and several heat stress with THI outcomes greater than 75 (Hahn et al., 2009; Herbut et al; 2018). Hence, in that the environment was not warm enough. In other words, it did not lead the animals to a real heat stress condition. Therefore, more data with greater THI in tropical conditions with beef cattle water intake measurements must be evaluated. We concluded that THI and water intake were not related, and more data should be provided to enhance this prediction.