<b>Heat stress on diet selection by cattle</b> - DOI: 10.4025/actascianimsci.v31i3.6293

Abstract

The ability of cattle to select the roughage and concentrate in their diets under different environmental temperatures was studied in 12 cannulated cows, during 30 days. The experimental design was completely randomized with two treatments: thermal comfort (21^oC) and thermal stress (climatic chamber, 38^oC). Cows were fed a diet of sugar cane plus urea and concentrate mixture, which were offered separately and ad libitum. The ability of cows to select their diets was identified by comparing the composition of diet selected in different environments, as weel as ruminal parameters and diet digestibility. A significant decrease (p < 0.05) of 22% on total dry matter intake was observed in animals kept under heat stress compared to animals kept under comfort temperature, while concentrate:roughage ratio chosen was similar for both treatments. Ruminal parameters were equal for both treatments, while digestibility of dry matter and some of its fraction were reduced in stressed animals. Animals under heat stress decreased dry matter intake without changing dietary energy or fiber levels, probably attempting to maintain the stability of ruminal environment.