Table 3.
Influence of treatments on characteristics of ruminal and total tract digestion in Holstein steers
| Item | Treatments1 | SEM2 | U-4.5 vs OPT-4.5 | S:F ratio | ||||
|---|---|---|---|---|---|---|---|---|
|
|
|
|||||||
| U-4.5 | OPT-6 | OPT-4.5 | OPT-3 | Linear | Quadratic | |||
| Intake (g/d) | ||||||||
| DM3 | 4,664 | 4,646 | 4,637 | 4,469 | 64 | 0.02 | 0.03 | 0.03 |
| OM4 | 4,403 | 4,419 | 4,387 | 4,370 | 61 | 0.08 | <0.01 | 0.31 |
| Starch | 1,903 | 2,239 | 2,084 | 1,761 | 27 | <0.01 | <0.01 | 0.01 |
| ADF5 | 452 | 374 | 501 | 602 | 7 | <0.01 | <0.01 | 0.01 |
| N6 | 93 | 100 | 102 | 101 | 1.7 | <0.02 | 0.25 | 0.11 |
| GE (Mcal/d)7 | 21.69 | 21.53 | 21.36 | 21.01 | 0.39 | 0.01 | 0.01 | 0.10 |
| Ruminal digestion (%) | ||||||||
| OM | 54.23 | 56.35 | 55.29 | 54.85 | 0.62 | 0.27 | 0.13 | 0.71 |
| Starch | 77.98 | 78.18 | 78.00 | 78.36 | 0.62 | 0.99 | 0.85 | 0.73 |
| ADF | 26.37 | 19.09 | 26.74 | 27.42 | 1.97 | 0.90 | 0.03 | 0.19 |
| Feed N | 66.22 | 67.02 | 68.38 | 65.50 | 1.10 | 0.15 | 0.29 | 0.12 |
| Duodenal flow of N (g/d) | 94.18 | 98.20 | 101 | 98.47 | 2.7 | <0.01 | 0.86 | 0.03 |
| Duodenal flow of MN (g/d)8 | 61.06 | 61.58 | 65.70 | 60.60 | 2.01 | <0.01 | 0.30 | <0.01 |
| MN efficiency9 | 25.55 | 24.73 | 27.05 | 25.29 | 0.44 | 0.02 | 0.22 | 0.03 |
| Duodenal flow of NAN (g/d)10 | 92.52 | 94.68 | 97.80 | 95.45 | 0.83 | <0.01 | 0.54 | 0.04 |
| N efficiency11 | 0.99 | 0.94 | 0.96 | 0.94 | 0.01 | 0.09 | 0.95 | 0.24 |
| Postruminal digestion (% leaving abomasums) | ||||||||
| OM | 65.84 | 64.62 | 63.28 | 60.86 | 1.28 | 0.21 | 0.09 | 0.74 |
| Starch | 94.29 | 94.62 | 94.78 | 94.96 | 0.34 | 0.35 | 0.76 | 0.82 |
| ADF | 22.47 | 17.96 | 14.33 | 12.68 | 2.40 | 0.07 | 0.17 | 0.75 |
| N | 75.55 | 76.56 | 77.64 | 76.86 | 4.9 | 0.02 | 0.68 | 0.18 |
| Total-tract digestion (%) | ||||||||
| DM | 77.65 | 78.89 | 76.81 | 75.10 | 0.57 | 0.28 | <0.01 | 0.77 |
| OM | 78.92 | 80.39 | 78.59 | 76.26 | 0.64 | 0.70 | <0.01 | 0.73 |
| Starch | 98.74 | 98.83 | 98.85 | 98.87 | 0.08 | 0.40 | 0.74 | 0.99 |
| ADF | 42.99 | 33.68 | 37.37 | 36.87 | 0.80 | <0.01 | 0.03 | 0.09 |
| N | 75.28 | 77.08 | 77.75 | 77.48 | 0.64 | <0.01 | 0.55 | 0.42 |
| DE (%)12 | 78.30 | 78.94 | 78.23 | 76.26 | 0.53 | 0.91 | <0.01 | 0.33 |
| DE diet (Mcal/kg) | 3.64 | 3.66 | 3.60 | 3.44 | 0.02 | 0.27 | <0.01 | 0.10 |
| Observed-to-expected DE | 1.00 | 1.00 | 1.02 | 1.00 | 0.006 | 0.04 | 0.69 | 0.04 |
U-4.5 = Diet formulated to supply 2.14 Mcal/kg of NEm with a ratio of starch:FDA of 4.5, containing 0.80% of conventional urea as the sole source of NNP; OPT-6 = Diet formulated to supply 2.14 Mcal/kg of NEm with a ratio of starch:FDA of 6.0, containing 0.80% of conventional urea plus 1.00% of Optigen; OPT-4.5 = Diet formulated to supply 2.07 Mcal/kg of NEm with a ratio of starch:FDA of 4.5, containing 0.80% of conventional urea plus 1.00% of Optigen, and OPT-3 = Diet formulated to supply 2.00 Mcal/kg of NEm with a ratio of starch:FDA of 3.0, containing 0.80% of conventional urea plus 1.00% of Optigen (OPT-3).
SEM = Standard error.
DM = Dry matter.
OM = Organic matter.
ADF = Acid detergent fiber.
N = Nitrogen.
GE = Gross energy.
MN = Microbial nitrogen.
Microbial efficiency is expressed as duodenal MN, g/kg OM fermented in the rumen.
NAN = Non-ammonia N.
N efficiency is expressed as duodenal non-ammonia N, g/g N intake.
DE = Digestible energy.