Effect of condensed tannin extract supplementation on growth performance, nitrogen balance, gas emissions, and energetic losses of beef steers

Condensed tannins (CT) may decrease greenhouse gas emissions and alter the site of N excreted by ruminants. We evaluated the effect of top-dressing a steam-flaked corn-based finishing diet (14.4% CP and NEg 1.47 Mcal/kg) for beef cattle with a commercially available CT extract at 3 levels (0, 0.5, and 1.0% of diet, DM basis). Angus-crossbred steers (n = 27; 350 +/- 32 kg initial BW) were individually fed via Calan gates for 126 d. Diet digestibility and N balance were estimated after 34 and 95 d on feed (Phase 1 and Phase 2, respectively) using titanium dioxide as a marker of fecal output and the creatinine: BW ratio as a marker for urine output. Ruminal CH4 and metabolic CO2 fluxes were measured using a GreenFeed system (C-Lock Inc., Rapid City, SD) for 2 sampling periods that coincided with fecal and urine sampling. Urine energy loss was estimated from urine N excretion, assuming all excreted N was urea. Oxygen consumption was estimated from CO2 production assuming a respiratory quotient of 1.05. Average daily gain (2.08, 2.14, and 2.08 kg/d for 0, 0.5, and 1.0% CT, respectively) and G:F did not differ (P = 0.88) among treatments. Starch intake and OM intake did not differ (P >= 0.42) among treatments during each phase. Apparent total tract starch digestibility during Phase 1 linearly decreased (P = 0.04) with inclusion of CT. Apparent total tract digestibility of OM and starch were not different among treatments (P >= 0.13) during Phase 2. Nitrogen intake did not differ (P >= 0.16) among treatments during each phase, but fecal N excretion linearly increased (P = 0.05) with inclusion of CT during Phase 1. Urinary N excretion was not different (P >= 0.39) among treatments during both phases, but urinary N as a proportion of total N excretion linearly decreased (P = 0.01) when CT was included in the diet during Phase 1. Retained N was not different (P >= 0.27) among treatments during each phase. Fluxes of CO2 were similar (P >= 0.37) among treatments during both phases. No differences (P >= 0.23) were observed for percentage of GE intake lost as CH4 (2.99, 3.12, and 3.09% in Phase 1 and 3.54, 3.55, and 4.35% in Phase 2) for 0, 0.5, and 1.0% CT, respectively. No difference (P >= 0.42) was observed for heat production lost as a percent of GE intake during both phases. Growth performance, gas emissions, and energetic losses were not affected by the inclusion CT in a steam-flaked corn-based finishing diet.