Table 4.
Effects of supplementation with different sources of nitrogen on the balance of nitrogen and AA digestibility of Nellore cattle grazing low-quality forage in the dry season.
| Supplement (S) 1 | SEM 2 | p-Value 3 | ||||
|---|---|---|---|---|---|---|
| Item | NPN | CGM | Time | S | Time × S | |
| n | 8 | 8 | ||||
| N-NH3, mg/dL | 24.4 | 23.1 | 0.331 | <0.001 | 0.327 | 0.624 |
| Microbial-N, g/d | 26.3 | 30.1 | 6.412 | - | 0.844 | - |
| Bacterial efficiency 4 | 116.9 | 160.7 | 26.89 | - | 0.638 | - |
| Nitrogen balance, g/d | ||||||
| Urinary-N excretion | 28.2 | 30.6 | 2.636 | - | 0.424 | - |
| Fecal-N excretion | 35.4 | 32.4 | 0.857 | - | 0.056 | - |
| Retained-N | 14.9 | −4.33 | 7.590 | - | 0.320 | - |
| Essential amino acids (EAA) digestibility, g/kg of DM | ||||||
| Arginine | 592.9 | 598.6 | 20.18 | - | 0.626 | - |
| Histidine | 596.9 | 608.0 | 22.82 | - | 0.923 | - |
| Isoleucine | 584.0 | 589.8 | 21.73 | - | 0.947 | - |
| Leucine | 599.9 | 639.8 | 24.78 | - | 0.822 | - |
| Lysine | 670.3 | 661.1 | 15.63 | - | 0.691 | - |
| Methionine | 700.0 | 695.7 | 21.35 | - | 0.322 | - |
| Phenylalanine | 582.7 | 612.3 | 21.85 | - | 0.978 | - |
| Threonine | 559.9 | 559.0 | 24.06 | - | 0.707 | - |
| Valine | 569.9 | 580.4 | 21.26 | - | 0.871 | - |
| Non-essential AA (NEAA) digestibility, g/kg of DM | ||||||
| Alanine | 522.4 | 559.5 | 30.90 | - | 0.792 | - |
| Aspartic Acid | 680.8 | 681.4 | 27.80 | - | 0.978 | - |
| Cystine | 652.0 | 683.7 | 21.36 | - | 0.952 | - |
| Glutamic Acid | 592.7 | 616.6 | 28.92 | - | 0.915 | - |
| Glycine | 555.4 | 542.1 | 24.57 | - | 0.825 | - |
| Proline | 536.3 | 581.4 | 29.33 | - | 0.901 | - |
| Serine | 529.1 | 547.3 | 29.97 | - | 0.964 | - |
| Tyrosine | 648.6 | 666.7 | 19.41 | - | 0.869 | - |
| AA total, g/kg of DM | 598.8 | 615.7 | 23.25 | - | 0.979 | - |
| EAA, g/kg of DM | 602.9 | 616.0 | 20.53 | - | 0.863 | - |
| NEAA, g/kg of DM | 591.5 | 609.8 | 26.22 | - | 0.956 | - |
1 NPN = Supplementation of urea as a source of NPN (50% of the daily requirement of RDP); CGM = supplementation of corn gluten meal 60 as the source of RUP (3 g/kg of BW per day). 2 SEM = standard error of the mean. 3 Time = effects of sampling time; S = effects of supplement; and Time × S = interaction between treatment and time. 4 Calculated as g of bacterial N/kg of OM truly digested.