Utilização de tanino de Acácia Negra (Acacia mearnsii de Wild) como atenuante do estresse térmico em vacas leiteiras

Abstract

The hypothesis of this work is that the use of Condensed Tannins from Black Acacia (Acacia mearnsii de Wild) increases the supply of non-degradable proteins in the rumen (PNDR), mitigating the effects of heat stress. This dissertation is composed of two experiments, A and B, whose objectives were to evaluate the use of different doses of condensed tannins from Black Acacia (Acacia mearnsii de Wild) in heat stress, composition and milk production in medium and high production dairy cows. Each experiment lasted 39 and 29 days, respectively. Both experiments were carried out using 20 cows. Selection parameters were milk production and number of days in lactation (DIL). Cows were distributed into two groups: tannin (TG) and control (CG). In experiment A, the TG animals received a dose of 150g of tannin / cow / day offered together with 600g of concentrate, while the animals in the group identified as CG, consumed the same dose of concentrate without any treatment. In experiment B TG animals received 40 g of tannin/cow/day and 10 g kaolin/cow/day and CG animals received 50g kaolin/cow/day. During the experiments we evaluated milk production and quality, the internal temperature of the cows as well as the temperature and humidity index (THI). Milk production was monitored daily and individually. To analyze milk composition weekly samples were taken and sent to specialized laboratories. Internal temperatures were measured using data logger intravaginal thermometers (Thermochron ibutton. KY -USA). The THI was monitored using a weather station. Mean THI in experiments A and B were 69.8 e 72.44, respectively. Milk production did not differ between groups. Nevertheless, TG In experiment A, the TG animals received a dose of 150g of tannin / cow / day offered together with 600g of concentrate, while the animals in the group identified as CG, consumed the same dose of concentrate without any treatmentanimals had higher protein concentrations and thermoregulation in both experiments (protein concentration A p= 0.02 and B p=0.007; thermoregulation A e B p<0.01). Dietary supplementation with tannins in both doses tested here (40 and 150 g/cow/day) increases thermotolerance and increases protein concentration in the in milk.