Feeding condensed tannins to mitigate ammonia emissions from beef feedlot cattle fed high protein finishing diets containing distillers grains.
JOURNAL OF ANIMAL SCIENCE(2018)
摘要
Two experiments were conducted to determine the effects of feeding a condensed tannin extract (CT) on dry matter intake (DMI), growth performance, carcass traits, and NH3-N emissions of beef feedlot cattle fed high-protein barley-based finishing diets. In Exp. 1, 36 crossbred steers (346 +/- 4.2 kg) were individually fed 4 diets with 20% corn dried distillers grains (DG) and increasing concentrations of a CT extract from Acacia mearnsii (black wattle) at 0%, 1.2%, 2.4%, and 3.5% of DM (9 steers per diet) for 52 d. The DMI was not affected at 1.2% and 2.4% but tended (P = 0.08, quadratic effect) to decrease at 3.5% CT extract. There was no effect (P >= 0.12) of increasing CT extract on ADG, but G: F tended (P = 0.09) to decrease linearly. In Exp. 2, 148 crossbred steers (457 +/- 3.8 kg) were allocated to 16 pens with 4 pens per treatment in a completely randomized design and fed for 83 d. The 4 dietary treatments included 0% corn DG (0DG), 20% DG (20DG), 40% DG (40DG), and 40% DG with 2.5% CT extract (40DGCT) and contained 13.3, 15.9, 20.4, and 19.4% CP, respectively. All cattle were weighed, and blood was collected from 5 steers per pen every 3 wk. Ammonia emissions were measured in four 3-wk periods using the integrated horizontal flux technique with passive NH 3 samplers from 2 pens of cattle fed 0DG and 20DG (Period 1), 40DG and 40DGCT (Period 2), 0DG and 40DG (Period 3), and 0DG and 40DGCT (Period 4). There was no effect (P = 0.15) of diet on final body weight (621 +/- 7.1 kg), DMI (11.9 +/- 0.25 kg/d), ADG (1.98 +/- 0.07 kg/d), G: F (166 +/- 5.4 g/kg), and carcass traits. Plasma urea N (PUN) increased (P < 0.001) from 0DG to 40DG (113 to 170 +/- 6.0 mg N/L) and was reduced (P < 0.001) by 40DGCT (146 mg N/L) compared with 40DG and tended (P = 0.09) to be reduced compared with steers fed 20DG (153 mg N/L). Ammonia-N emissions were greater from cattle fed 40DG [113.7 vs. 70.8 +/- 4.57 g N/(steer center dot d), P = 0.003] and tended to be greater from cattle fed 20DG [51.3 vs. 26.3 +/- 11.2 g N/(steer center dot d), P = 0.11] compared with 0DG. Cattle fed 40DGCT tended to have lower NH 3-N emissions compared with cattle fed 40DG [72.7 vs. 95.1 +/- 9.3 g N/(steer center dot d), P = 0.09 and 20.5 vs. 26.5 +/- 2.64% N intake, P = 0.11]. Feeding 2.5% CT to beef feedlot cattle fed a high-protein diet had no detrimental effect on performance, reduced PUN indicating lower urinary urea N excretion, and lowered NH3-N emissions by 23%.
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关键词
ammonia,condensed tannins,corn distillers grains,feedlot cattle,growth performance
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