Influência do índice de temperatura e umidade no consumo alimentar em touros Nelore participantes de provas de eficiência alimentar em ambiente tropical

Abstract

With global climate change, an evident concern is the impact of increasing air temperature on cattle physiology, especially in tropical countries. In this context, the objective was to analyze the influence of the thermal environment on the ingestive behavior of confined Nellore bulls participating in a feed efficiency test. For this, 51 Nellore bulls with an average age of 19 months, non-castrated, with an average initial weight of 426 ± 36 kg, confined for 92 days and evaluated in the GrowSafe® electronic system were used. A total of 321,812 observations were recorded, but only valid days without errors were kept for analysis, resulting in 32,702 observations. The variables studied were average natural matter intake (NMI), number of visits to the feed bunk with consumption (NVC), and average feeding time (AFT), daily, every hour. The THI was categorized as cold (THI ≤ 40), thermoneutral (41 ≤ THI ≤ 74), and heat (THI ≥ 75) every 1 hour throughout the day. Data were evaluated by the Kruskal-Wallis test followed by Dunn's test at 5%. The NMI was higher during the thermoneutral period compared to cold and heat conditions. For NVC, there was a higher number of visits in the heat class compared to the thermoneutral and cold classes. AFT was higher under cold THI, progressively decreasing in thermoneutral THI condition, followed by heat THI. It is concluded that in the Cerrado Biome, THI values from 75 to 81 in the dry season (May to August) negatively influence the ingestive behavior of confined Nellore bulls participating in feed efficiency tests, despite being considered well-adapted to heat.