Efeito do ambiente térmico sobre a ingestão de matéria seca e comportamento alimentar em touros Senepol confinados em região tropical

Abstract

The complexity of the thermal environment, as well as its influence on the productive performance of animals need to be better understood, to improve zootechnical indices and animal welfare. Therefore, in this study, the purpose was to investigate the influence of the thermal environment on dry matter intake, frequency and time in the feed bunk in Senepol bulls confined in tropical region. This research was conducted at Fazenda Capim Branco, from Federal University of Uberlândia, Uberlândia, MG. In the summer (12/24/2019 to 03/03/2020), 31 unneutered male bovines, with 14.5 ± 0.76 months and average body weight of 409.94 ± 48.73 kg were confined in a pen with electronic feed bunkers of the Growsafe® system for 91 days, with 21 destined for adaptation. The diet consisted of 60% roughage and 40% concentrate¸ supplied twice a day. The Growsafe system monitored in real time the consumption of natural matter, number of visits to the bunk feeders and time spent in the bunk. The dry matter intake (DMI), dry matter intake in relation to body weight (DMI%BW), total number of visits to the feed bunk (TFV), number of visits with consumption (NVC), time at the feed bunk (TF) and relative number of visits to the feed bunker (NV/NVC) were determined. Air temperature and humidity data were recorded by dataloggers, every thirty minutes, daily. Wind speed, maximum and minimum temperatures in 24 hours, and the temperature of the globe thermometer were also determined. The Temperature and Humidity Index (THI) and the Heat Load Index (HLI) were calculated. The THI was divided into 4 classes: THI1 ≤ 74 (thermoneutral); THI2= 74<THI≤79 (alert); THI3= 79<THI≤84 (danger) and THI4= THI>84 (emergency) and the HLI in HLI1 ≤91 and HLI2 >91. The design was completely randomized, the database was submitted to exploratory analysis for detection and removal of outliers. ANOVA and Tukey test or Student t were used. A significance level of 5% was considered. The DMI, DMI%BW, TFV, TF NVC, NVCT were higher in thermoneutral class compared to danger and emergency classes. The DMI, DMI%BW, TFV, TF, NVC and TVF of confined Senepol bulls raised under an environment with ITU values above 74 are reduced.