Effects of rumen-protected arginine supplementation and arginine-HCl injection on site and extent of digestion and small intestinal amino acid disappearance in forage-fed steers

• Published in: Translational animal science 2018-04, Vol.2 (2), p.205-215
• Main Authors: Meyer, Allison M, Klein, Sharnae I, Kapphahn, Marsha, Dhuyvetter, Dan V, Musser, Robert E, Caton, Joel S
• Format: Article
• Language: English
• ISSN: 2573-2102
• DOI: 10.1093/tas/txy007

Four ruminally and intestinally cannulated steers were used in a 4 × 4 Latin square to evaluate effects of rumen-protected Arg supplementation or intravenous Arg injection on small intestinal delivery of AA, site and extent of digestion, and ruminal fermentation. Steers were fed grass hay (7.2% CP, 67.6% NDF, 0.29% Arg) for ad libitum intake with no additional Arg (CON), 54-mg L-Arg/kg BW injected intravenously (Arg-INJ), 180-mg rumen-protected L-Arg/kg BW daily (Arg-RP180), or 360-mg rumen-protected L-Arg/kg BW daily (Arg-RP360). Half of each treatment dose was administered twice daily. Each period had a 7-d washout of hay only followed by a 14-d treatment and collection period. Ruminal disappearance (%) of Arg was greater ( < 0.001) for both Arg-RP treatments than CON and Arg-INJ, although the amount of Arg disappearing was greatest in Arg-RP360, followed by Arg-RP180, and least in CON and Arg-INJ ( < 0.001). Duodenal flow and small intestinal disappearance (g/d) of Arg was greatest in Arg-RP360, followed by Arg-RP180, and least in CON and Arg-INJ ( < 0.004). Ileal flow of Arg was greatest in Arg-RP360, intermediate in Arg-RP180, and least in CON ( = 0.01) because the proportional small intestinal disappearance of Arg was not different ( = 0.96). Steers fed Arg-RP360 had greater ( = 0.01) ileal flow of Orn and tended to have greater ( = 0.09) ileal flow of Glu than all other treatments. There were no differences in hay or total DMI, microbial efficiency, or OM, NDF, or ADF digestibility ( ≥ 0.10). Total N intake and duodenal N flow were greater in Arg-RP360 than all other treatments ( ≤ 0.02). Total tract N digestibility was greatest in Arg-RP360, followed by Arg-RP180, and least in CON and Arg-INJ ( = 0.003). Ruminal ammonia was greater ( = 0.004) in Arg-RP360 compared with CON and Arg-INJ and greater ( = 0.06) in Arg-RP180 than CON. There was no effect of treatment ( ≥ 0.37) on total VFA, acetate, propionate, or butyrate concentrations. Results indicate that feeding rumen-protected Arg increases small intestinal Arg flow with minimal effects on ruminal fermentation and total tract digestibility of OM and fiber.