1. Modeling to estimate the mean surface Temperature of Calves JOÃO BATISTA FREIRE DE SOUZA JR, MAIKO ROBERTO TAVARES DANTAS, RENATA NAYHARA DE LIMA, JOÃO PAULO ARAÚJO FERNANDES DE QUEIROZ, GEOVAN FIGUEIRÊDO DE SÁ FILHO, JÂNIO LOPES TORQUATO, PATRÍCIA DE OLIVEIRA LIMA, LEONARDO LELIS DE MACEDO COSTA Universidade Federal Rural do Semi-Árido (UFERSA)
Introduction The temperature of calves is not distributed homogeneously throughout the body surface. In heat stress situations, some body parts are heated faster than others, indicating its greater contribution to heat dissipation. Therefore, what is the mean surface temperature of calves? The aim of this study was to develop a mathematical model to estimate the MST of calves using temperatures measured in different body regions.
Material and Methods The study was conducted in Mossoro, RN state, Brazil (05°11' South, 37°22' West and 16 m above sea level). Twenty three crossbred calves (3/4 Holstein, ¼ Zebu undefined breed), aged 30 and 90 days, were used. Measurements were made during the period from 07:00 to 18:00. Environmental variables were collected: air temperature (TA, °C), relative humidity (RH, %), wind speed (Vv, m/s), and mean radiant temperature (MRT, °C). With a portable thermal imager, thermal images of four body regions were obtained: face (TFA °C), neck (TPE °C), hindquarters (TQT, °C), and flank (TFL, °C). A multiple linear regression analysis was performed using the PROC REG function of the SAS software to check which body regions significantly contributed to the MST.
Figure 1. Thermal image of a calf obtained during the study. Body regions selected are highlighted.

2. Results and Discussion
Modeling to estimate the mean surface Temperature of Calves JOÃO BATISTA FREIRE DE SOUZA JR, MAIKO ROBERTO TAVARES DANTAS, RENATA NAYHARA DE LIMA, JOÃO PAULO ARAÚJO FERNANDES DE QUEIROZ, GEOVAN FIGUEIRÊDO DE SÁ FILHO, JÂNIO LOPES TORQUATO, PATRÍCIA DE OLIVEIRA LIMA, LEONARDO LELIS DE MACEDO COSTA Universidade Federal Rural do Semi-Árido (UFERSA)
Results and Discussion
Table 2. Means and standard errors of body surface temperature in the different regions analyzed.
Conclusion
Therefore, we conclude that this equation can be a useful tool for future studies addressing the effect of heat stress on calves.
Table 1. Means and standard errors of environmental variables.
Variable
Mean ± Standard Error
TFA (°C)
35.42 ± 0.07
TPE (°C)
32.44 ± 0.09
TFL (°C)
TQT (°C)
33.04 ± 0.09
Variable
Mean ± Standard Error
TA (°C)
28.63 ± 0.08
UR (%)
65.80 ± 0.36
Vv (m/s)
0.31 ± 0.01
MRT (°C)
30.08 ± 0.10
MST (°C) = x TQT x TFA x TPE x TFL
This model presented an adjusted R2 of 0.98. 
TFA: face temperature; TPE: neck temperature; TFL: flank temperature; TQT: Hindquarters temperature
TA: Air temperature; UR: Relative humidity; Vv : Wind speed; MRT: Mean radiant temperature.