Thermal sum (degrees-days) rest period as a grazing management tool in natural grasslands: Effects on animal performance and forage production

Abstract

This study evaluates the use of thermal sum rest periods on natural grassland as a grazing management tool. We evaluated the impact of this grazing management on vegetation and its effects on the performance of beef heifers in the Pampa biome (southern Brazil) after three years of using this schedule. A complete randomized block design experiment with two treatments and three replications was conducted with Angus heifers as animal replicates. The treatments were two thermal sums calculated at 375 and 750 degrees-days to determine the rest intervals between grazing periods in a rotational grazing system. The experiment was conducted on beef cattle heifer testers with an average age of seven months and a weight of 150.5 ± 5 kg at the start of the experiment. Each heifer received a whole rice bran supplement at a rate of 1.0% of body weight per day during the cool season (April to September) and had free access to mineral supplements. Treatments carried out in different periods had similar herbage mass, feed intake, chemical composition, and animal performance. Thermal sum rest intervals could be a valuable grazing management tool to improve animal production per area, forage quality, and high animal stocking rate.