Table 2.
Effects of rumen-protected L-Arg (RP-Arg) supplementation or intravenously injected L-Arg-HCl on DMI and OM intake and site of digestion in forage-fed steers
| Treatmentsa | ||||||
|---|---|---|---|---|---|---|
| Item | CON | Arg-INJ | Arg-RP180 | Arg-RP360 | SEM | P-value |
| Total DMI, kg/d | 7.76 | 8.09 | 7.25 | 8.92 | 0.95 | 0.29 |
| Hay DMI, kg | 7.76 | 8.09 | 7.12 | 8.67 | 0.95 | 0.34 |
| RP-Arg DMI, g/d | 0b | 0b | 122b | 242c | 1.0 | <0.001 |
| Total OM intake, kg/d | 7.03 | 7.32 | 6.45 | 7.85 | 0.86 | 0.34 |
| Duodenal OM flow, kg/d | 3.21 | 3.11 | 3.22 | 3.65 | 0.36 | 0.48 |
| Bacterial OM flow | 0.543 | 0.477 | 0.523 | 0.551 | 0.047 | 0.31 |
| Apparent feed OM | 2.67 | 2.64 | 2.70 | 3.09 | 0.32 | 0.51 |
| Ileal OM flow, kg/d | 2.62 | 2.90 | 2.66 | 3.06 | 0.28 | 0.53 |
| Fecal OM output, kg/d | 2.38 | 2.68 | 2.51 | 2.88 | 0.30 | 0.20 |
| OM digestibility, % of intake | ||||||
| Apparent ruminal | 53.1 | 57.5 | 48.5 | 53.8 | 3.2 | 0.20 |
| True ruminale | 61.1 | 64.0 | 56.2 | 59.4 | 3.1 | 0.26 |
| Apparent small intestinal | 17.2 | 8.6 | 14.8 | 14.8 | 3.2 | 0.14 |
| Apparent large intestinal | −5.20 | −2.66 | −3.93 | −5.71 | 3.41 | 0.82 |
| Apparent total tract | 65.6 | 63.7 | 59.8 | 62.0 | 2.6 | 0.12 |
aTreatments included: ad libitum intake of grass hay (CON), CON with 27 mg L-Arg-HCl/kg BW injected intravenously twice daily (54 mg/kg BW daily; Arg-INJ), CON with 90 mg rumen-protected L-Arg/kg BW supplemented twice daily (180 mg/kg BW daily; Arg-RP180), and CON with 180 mg rumen-protected L-Arg/kg BW supplemented twice daily (360 mg/kg BW daily; Arg-RP360).
b,cMeans within a row without a common letter superscript differ (P ≤ 0.05).
eCorrected for OM of bacterial origin.