Table 3.
Influence of dietary Zn and ractopamine supplementation on DMI, diet digestibility, and daily urine and fecal output during 5-d collection period
| Dietary treatment | ZNTRT1 | BA1 | |||||
|---|---|---|---|---|---|---|---|
| CON2 | SUPZN2 | P value4 | NON3 | RAC3 | P value4 | SEM | |
| Steers (n) | 16 | 15 | 15 | 16 | |||
| DMI5, kg/d | 9.43 | 10.12 | 0.40 | 9.89 | 9.67 | 0.78 | 0.558 |
| DMD6, % | 80.71 | 80.76 | 0.97 | 81.09 | 80.38 | 0.61 | 0.946 |
| OMD7, % | 81.95 | 82.19 | 0.84 | 82.49 | 81.65 | 0.51 | 0.869 |
| N intake, g/d | 210.3 | 224.0 | 0.45 | 218.3 | 216.0 | 0.90 | 12.31 |
| Daily output | |||||||
| Fecal, kg DM/d | 1.85 | 1.96 | 0.66 | 1.90 | 1.91 | 0.98 | 0.173 |
| Urine, L/d | 8.85 | 8.56 | 0.82 | 10.13 | 7.23 | 0.05 | 0.876 |
| Fecal, N g/d | 46.8 | 49.8 | 0.58 | 48.2 | 48.4 | 0.97 | 3.79 |
| Urine, N g/d | 78.5 | 75.8 | 0.58 | 84.5 | 69.8 | 0.01 | 3.35 |
| N retention, g/d | 85.1 | 98.8 | 0.20 | 86.1 | 97.8 | 0.27 | 7.03 |
| N retention8, % | 40.0 | 44.3 | 0.05 | 39.5 | 44.8 | 0.02 | 1.38 |
1ZNTRT (mineral supplementation strategy); BA (β-adrenergic agonist supplementation strategy).
2CON (no supplemental Zn; analyzed 32 mg Zn/kg DM); SUPZN [CON + 60 ppm ZnSO4 + 60 ppm zinc-amino acid complex (Availa-Zn; Zinpro, Eden Prairie, MN), analyzed 145 mg Zn/kg DM].
3NON (no supplemental ractopamine HCl); RAC (300 mg steer−1 d−1 ractopamine HCl; Actogain 45, Zoetis, Parsippany, NJ).
4ZNTRT × BA interaction was not significant (P ≥ 0.19).
5DMI over 5-d period during collection.
6DMD = DM digestibility.
7OMD = OM digestibility.
8Reported as percentage of intake.