419 Effect of Differing Rates of Quebracho (Schinopsis balansae) Extract provided in a Limit-Fed High Roughage Total Mixed Ration Upon Digestibility and Nitrogen Balance.

Abstract

Our objective was to determine the effect of quebracho tannin extract (QT; Schinopsis balansae) within a high roughage diet upon digestibility and N balance. Use of natural compounds as rumen modulators has remained a critical area of research due to increased regulation upon feed additive use, environmental emissions, and consumer perception of the animal industry. Condensed tannins (CT) show promise as a feed additive due to the potential for improved N efficiency and decreased CH ₄ emissions. However, there is limited data regarding the effect of CT on digestibility and N balance when limit-feeding a high roughage diet. A 4x8 Latin rectangle design with eight steers (443 ± 20 kg) and four dietary treatments was utilized to evaluate the following dietary treatments: no QT (QT ₀) or addition of QT at 1.5, 3, or 4.5% of DM. Diets were fed at 1.7% of shrunk body weight. Steers were adapted to diets for 10-d and placed into metabolism crates on days 11 to 14 for total urine and feces collection. Samples were composited by animals within periods and analyzed for total N and gross energy (GE), as well as neutral detergent fiber (NDF) and acid detergent fiber (ADF) for feed and fecal samples. Dietary treatment impacted dry matter digestibility, NDF digestibility, and ADF digestibility ( P≤ 0.001) in which QT ₀ and QT _1.5 had the greatest digestibilities. This resulted in a 10% greater efficiency, on average, for digestible energy to GE ratio ( P = 0.0001) for QT ₀ and QT _1.5. In contrast, there were no observed differences for N retention ( P = 0.22), but the proportion of N excreted within the feces increased with QT inclusion rate ( P = 0.005). The addition of QT at 1.5% DM to a limit fed high roughage diet does not sacrifice digestibility, digestible energy to GE ratio, or N balance.