Table 3.
Nitrogen balance of bulls fed with different crude protein levels
| Item | Treatment1 | Contrasts3 | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| LO | MD | HI | LH | LM | MH | SEM2 | Linear | Quadratic | M x LH | Mx LM | M x MH | |
| N intake, g/d | 135.2 | 149.7 | 197.6 | 171.9 | 143.8 | 165.9 | 2.38 | <0.01 | <0.01 | 0.02 | <0.01 | <0.01 |
| N digested, % of intake | 67.9 | 70.5 | 73.0 | 71.1 | 67.2 | 69.91 | 0.60 | 0.02 | <0.01 | 0.38 | 0.01 | 0.03 |
| Fecal N, g/d | 43.9 | 44.3 | 52.1 | 49.4 | 47.0 | 50.0 | 1.21 | <0.01 | 0.01 | 0.07 | 0.81 | <0.01 |
| Urine N, g/d | 67.7 | 85.5 | 116.1 | 92.8 | 71.2 | 90.7 | 2.39 | <0.01 | <0.01 | 0.33 | <0.01 | <0.01 |
| Urine N, % of excreted N | 61.1 | 64.0 | 67.7 | 64.9 | 59.4 | 64.2 | 0.71 | <0.01 | <0.01 | 0.09 | <0.01 | <0.01 |
| Retained N, g/d | 23.8 | 29.0 | 29.1 | 29.9 | 26.4 | 27.3 | 1.16 | 0.96 | <0.01 | 0.13 | <0.01 | 0.04 |
| Retained N, % of N intake | 16.2 | 17.9 | 13.8 | 18.8 | 19.1 | 15.4 | 0.39 | <0.01 | 0.58 | <0.01 | 0.01 | 0.23 |
| Blood urea N, mg/dL | 11.2 | 21.5 | 23.8 | 11.8 | 10.7 | 20.9 | 1.72 | 0.49 | <0.01 | 0.84 | <0.01 | <0.01 |
1LO, low (105 g CP/kg DM); MD, medium (125 g CP/kg DM); HI, high (145 g CP/kg DM), LH, oscillating low (LO; 105 g CP/kg DM) to high (HI; 145g CP/kg DM) each 48 h; LM, oscillating low (105 g CP/kg DM) to medium (MD; 125 g CP/kg DM) each 48 h; MH, oscillating medium (125g CP/kg DM) to high (145g CP/kg DM) each 48 h.
2SEM = standard error of the mean.
3Linear and quadratic contrasts compared 105, 125, and 145 g CP/kg DM; M vs. LH compared 125 vs. oscillating 105 to 145 g CP/kg DM each 48 h; M vs. LM compared 125 vs. oscillating 105 to 125 g CP/kg DM each 48 h; M vs. MH compared 125 vs. oscillating 125 to 145 g CP/kg DM each 48 h.