Effects of encapsulated nitrate on growth performance, nitrate toxicity, and enteric methane emissions in beef steers: Backgrounding phase.

A long-term experiment was conducted to examine the effects of feeding encapsulated nitrate (EN) on growth, enteric methane production, and nitrate (NO) toxicity in beef cattle fed a backgrounding diet. A total of 108 crossbred steers (292 ± 18 kg) were blocked by BW and randomly assigned to 18 pens. The pens (experimental unit; 6 animals per pen) received 3 dietary treatments: Control, a backgrounding diet supplemented with urea; 1.25% EN, control diet supplemented with 1.25% encapsulated calcium ammonium NO (i.e., EN) in dietary DM, which partially replaced urea; or 2.5% EN, control diet supplemented with 2.5% EN (DM basis) fully replacing urea. Additionally, 24 steers were located in 4 pens and randomly assigned to 1 of the above 3 dietary treatments plus a fourth treatment: 2.3% UEN, control diet supplemented with 2.3% unencapsulated calcium ammonium NO (UEN) fully replacing urea. Animals in the additional 4 pens were used for methane measurement in respiratory chambers, and the pens (except UEN) were also part of the performance study (i.e., = 7 pens/treatment). The experiment was conducted for 91 d in a randomized complete block design. During the experiment, DMI was not affected by inclusion of EN in the diet. Feeding EN had no effect on BW, ADG, and G:F ( ≥ 0.57). Methane production (g/d) tended to decrease ( = 0.099) with EN and UEN, but yield (g/kg DMI) did not differ ( = 0.56) among treatments. Inclusion of EN in the diet increased ( ≤ 0.02) sorting of the diets in favor of large and medium particles and against small and fine particles, resulting in considerable increases in NO concentrations of orts without affecting DMI. Plasma NO-N and NO-N concentrations increased ( ≤ 0.05) for EN compared with Control in a dose response manner, but blood methemoglobin levels were below the detection limit. Nitrate concentration in fecal samples slightly increased (from 0.01% to 0.14% DM; < 0.01) with increasing levels of EN in the diet. In conclusion, EN can be used as a feed additive replacing urea in beef cattle during a backgrounding phase in the long term without NO intoxication or any negative effects on growth performance. In addition, the study confirmed that feeding EN tended to decrease enteric methane production in the long term.