Extrato de acacia mearsnsii como fonte de tanino condensado na alimentação de tourinhos Nelore

Abstract

Acacia mearnsii extract has been used as a source of condensed tannin (TC) and has the potential to improve nitrogen utilization in ruminant production. The aim of this study was to evaluate the effect of increasing levels of Acacia mearnsii as a source of TC on feed intake, nutrient digestibility, nitrogen balance and rumen fermentation in Nellore bulls finished in feedlot. Four crossbred, castrated cattle equipped with a rumen cannula, with an average body weight of 446 (± 34) kg were distributed in a 4 × 4 double Latin square design, repeated over time. Each Latin square lasted 68 days, divided into four experimental periods, 17 days each, with 10 days for adaptation of the animals and 7 days for data and sample collection. The treatments used consisted of a diet without the inclusion of Acacia mearnsii extract (0 g/kg) and three diets with 10, 30 and 50 g/kg based on dry matter (DM). The use of Acacia mearnsii extract containing TC in the diet reduced (P < 0.05) intake of DM, CP, EE, cpNDF and CNF. There was 23 an increase (P < 0.05) in DM, cpNDF, CNF and NDT digestibility, however, it did not affect (P = 0.1563) crude protein digestibility and microbial protein synthesis efficiency. The inclusion of Acacia extract provided a reduction in ingested nitrogen (P < 0.0001), excretion of N via urine (P = 0.0120). The excretion of N via feces increased quadratically (P = 0.0298) with maximum extract intake at the inclusion level of 10.09 g/kg DM, however, it did not affect the nitrogen balance (P = 0.8995). The concentration of ammoniacal nitrogen (N-NH3) and short-chain fatty acids (SCFA) were not affected by the inclusion of the extract. However, N-NH3 concentrations changed over time, with a maximum value of 10.74 mg/ dL at 3.10 hours. The ruminal pH reduced with the inclusion of the extract (P < 0.0001) and in relation to the collection time (P = 0.0009). There was no interaction between the effects of extract inclusion and time of collection. Therefore, Acacia mearnsii extract, in doses up to 50 g/kg DM or 35 g/kg TC, has the potential to be used as a source of tannin in the diet of young bulls finished in feedlot to improve the use of food and its nutrients. In addition to being advantageous from an environmental point of view by reducing nitrogen excretion.