This study addressed the dose-response effect of an encapsulated nitrate product (ENP) replacing soybean meal (SBM) in the finishing period (87-d) of feedlot bulls. One hundred twenty Nellore bulls (340 ± 28 kg of body weight, BW; mean ± SD) were allotted to 20 outdoor pens (6 animals/pen) and assigned to a randomized complete block design with 5 blocks based on initial BW and 4 dietary treatments: SBM, as control; ENP-10, 10 g ENP/kg dry matter (DM; 6.5 g NO₃⁻/kg DM); ENP-20, 20 g ENP/kg DM (13 g NO₃⁻/kg DM); and ENP-30, 30 g ENP/kg DM (19.5 g NO₃⁻/kg DM). Finishing diets (90:10 concentrate to roughage ratio) were formulated to provide similar amounts of nutrients. Animals were gradually and simultaneously adapted over 14 d to ENP and concentrate. Dry matter intake (DMI) reduced linearly (from 9.6 to 8.4 kg/d; P = 0.02) with ENP inclusion. Final BW, average daily gain (ADG), carcass ADG, hot carcass weight, dressing percentage, and fat thickness were not affected (P ≥ 0.12) by treatments. There was a quadratic trend for increased carcass gain:feed (0.121, 0.130, 0.128, 0.127, respectively; P = 0.07). Nitrate concentration in meat increased linearly (3.48, 2.73, 3.98, 6.59 mg NaNO₃/kg meat; P = 0.02) with ENP addition, although nitrite was not detected. Time spent eating (min/d) was similar (P ≥ 0.16) among treatments, whereas a linear increase (P = 0.02) was observed for time spent eating per unit of DMI when ENP was fed. There was a trend (P = 0.07) for a quadratic effect in ruminating time per unit of DMI according to ENP increments. Blood methemoglobin before morning feeding increased linearly (P < 0.01) on d 28 and 56 as more ENP was fed, however, values remained ≤ 3.57% of total hemoglobin. Increasing levels of ENP affected further blood metabolites, such as triglycerides (quadratic response, P < 0.01), total cholesterol (linear increase, P = 0.05), urea (linear decrease, P < 0.01), aspartate aminotransferase (linear decrease, P < 0.01), and gamma-glutamyl transferase (linear decrease, P = 0.04). In conclusion, finishing bulls fed ENP performed similarly to SBM, suggesting ENP as a promising nitrogen source. There was evidence of a possible improvement in carcass-based feed efficiency (a decrease in DMI associated with a similar carcass ADG) for bulls fed ENP, reaching a calculated maximum value for the inclusion rate of 17.7 g ENP/kg DM.

这项研究解决了在育肥公牛的肥育期（87天）中，硝酸盐封装产品（ENP）代替豆粕（SBM）的剂量反应效应。将一百二十只内洛尔公牛（体重340±28千克，体重；平均值±标准差）分配给20只室外围栏（6只动物/围栏），并根据最初的体重和4种饮食分配到5个整体的随机完全块设计中处理：SBM，作为对照；ENP-10，10g的ENP / kg干物质（DM;6.5克NO ₃ ^- /公斤DM）; ENP-20，20g的ENP / kg的DM（13克NO ₃ ^- /公斤DM）; 和ENP-30，30g的ENP / kg的DM（19.5克NO ₃ ^-/ kg DM）。配制日粮（精矿与粗饲料的比例为90:10）以提供相似量的营养。使动物在14 d内逐渐并同时适应ENP并集中注意力。 加入ENP后，干物质摄入量（DMI）线性降低（从9.6千克/天降低至8.4千克/天；P = 0.02）。最终BW，平均日增重（ADG），胴体ADG，热胴体重，屠宰率，和脂肪厚度并没有受到影响（P通过处理≥0.12）。car体增重：饲料的增加呈二次趋势（分别为0.121、0.130、0.128、0.127；P  = 0.07）。肉中硝酸盐浓度呈线性增加（3.48、2.73、3.98、6.59 mg NaNO ₃ / kg肉；P = 0.02）加上ENP，尽管未检测到亚硝酸盐。花费的时间吃（分钟/ d）是相似的（P ≥0.16）处理之间，而线性增加（P  = 0.02）观察到废每DMI的单元进食时ENP供给时间。 根据ENP增量，每单位DMI的思考时间存在二次趋势（P = 0.07）。早晨喂食前的血液高铁血红蛋白在第28天和第56天随着喂食更多的ENP呈线性增加（P <0.01），但其值仍≤总血红蛋白的3.57％。ENP水平升高会进一步影响血液代谢产物，例如甘油三酸酯（二次反应，P <0.01），总胆固醇（线性增加，P） = 0.05），尿素（线性下降，P <0.01），天冬氨酸转氨酶（线性下降，P <0.01）和γ-谷氨酰胺基转移酶（线性下降，P  = 0.04）。总之，饲喂ENP的肥牛表现与SBM相似，表明ENP是有希望的氮源。有证据表明，饲喂ENP的公牛的car体饲料效率可能提高（与类似car体ADG相关的DMI降低），达到17.7 g ENP / kg DM的包容率的计算最大值。