What is the best temperature-humidity index equation to indicate heat stress in crossbred dairy calves in a tropical environment?

Abstract

The aim of this study was to determine among nine temperature-humidity index (THI) equations, the one that best represents the effects of heat stress on crossbred dairy calves reared in a tropical environment. Twelve male and female calves, aged 20 to 60 days, and raised in a tropical pen were evaluated. Respiratory (RR) and heart rates (HR), rectal (RT), body surface (BST), dry bulb (Tdb) and wet bulb (Tbw) temperatures, partial vapor pressure (Pv), relative humidity (RH) and dew point temperature (Tpo) were quantified in the morning and afternoon. Nine THI equations were calculated. The highest correlation between physiological variables and this was used to select the best THI equation. Averages for nine THI equations, Tdb, Twb, Pv, Tdp, RR, HR, RT, and BST were higher in the afternoon than in the morning, whereas that for RH was the opposite. The highest values for RT occurred at temperatures above 26.4°C and when humidity was below 55.5%. The Tdb and Pv correlations with RR (0.697 and 0.707), RT (0.703 and 0.706) and BST (0.818 and 0.817) were significant and positive, whereas the RH correlations with the same physiological variables were significant and negative (-0.622, -0.590 and -0.638, respectively). The best index was the THI sensible heat-based ( T H I = 3.43 + 1.058 x T d b - 0.293 x R H + 0.0164 x T d b x R H + 35.7), which was significantly correlated with RR (r=0.668 and r²=0.446), HR (r=0.259 and r²=0.067), RT (r=0.693 and r²=0.479) and BST (r=0.807 and r²=0.650). In conclusion, the THI sensible heat-based equation best represents the effects of heat stress on crossbred dairy calves reared in a tropical environment.

Birth Rate and Birth Weight of Crossbred Calves in Andaman and Nicobar Islands

“…Further, it could be contemplated that temperature and humidity might be affecting the sexual desire of the animals. Comparatively less number of animals breeds during the month of heavy rain fall as because, only few animals are exhibit the estrus behaviour (Nascimento et al, 2019). Maximum number of animal bred in July, August and November.…”

Biometric Physiological Responses from Dairy Cows Measured by Visible Remote Sensing Are Good Predictors of Milk Productivity and Quality through Artificial Intelligence

“…All the different trends explored before can be seen in the PCA ( Figure 6 ). The THI9 was chosen for multivariate data analysis as it is the most correlated with physiological data and sensitive to describe heat stress in dairy cows [ 43 , 54 ]. In the case of wind, the speed vector is inversely related to physiological parameters, such as HR, RR and eye temperature.…”

Artificial Intelligence Applied to a Robotic Dairy Farm to Model Milk Productivity and Quality based on Cow Data and Daily Environmental Parameters

“…Based on these data, other variables such as dewpoint temperature (T dp ; • C; Equation (1); [15]), Sensors 2020, 20, 2975 3 of 11 wet bulb temperature (T wet ; • C), and THI were calculated. The latter was calculated using the following nine different equations (Equations ( 2)-( 10); [11] where T wet was calculated in batch using a customized code written in MATLAB®R2020a (Mathworks Inc., Natick, MA, USA; [16]), calculations were based on T, T dp , and surface pressure and the bisection search method.…”