Optimization of the national livestock sustainably

SUMMARY The objective of this work was to evaluate the calcium nitrate utilization in replacing to the soybean meal for ruminants diets under the mitigation of enteric methane aiming to determine the animal diet cost and the marginal costs for carbon rebates. The study was conducted in two stages, the first stage was in vitro gas production were performed in order to measure the enteric methane mitigation potential of the nitrate. The methane mitigation data were used in the second stage, which simulated a dairy farm with three feed systems: control system without nitrate, and systems with inclusion of 1.5 to 3% nitrate in the diet. The spreadsheets were used to evaluate the costs and revenues of each system resulting carbon credit sales of methane reduction in 10 years. The net present value (NPV) and the internal rate of return (IRR) were the indexes used in the financial evaluation.The carbon credit sale did not change the NPV significantly, however the inclusion of nitrate to 1.5 and 3% in animal feed showed economically feasible, because it reduced the diet value (R$5.89 e R$5.81/cow/day, respectively) in comparison to control diet (R$6.13/cow/day) besides contributing to the reduction and greenhouse gases. Therefore, the nitrate supplementation beside reduced the methane production, has the positive effect on the variable cost of the activity.

摘要 本研究旨在评估硝酸钙在反刍动物日粮中替代豆粕的应用效果，并开展瘤胃甲烷（enteric methane）减排调控，以明确动物日粮成本及碳减排补贴的边际成本。本研究分两阶段开展：第一阶段采用体外产气法（in vitro gas production）测定硝酸钙的瘤胃甲烷减排潜力；第二阶段利用第一阶段获得的甲烷减排数据，模拟设置三种饲喂系统的奶牛场：无硝酸钙添加的对照组饲喂系统，以及日粮中添加1.5%至3%硝酸钙的饲喂系统。借助电子表格模型评估各系统的成本与收益，并核算10年内甲烷减排所产生的碳信用额度销售收入。本次财务评价选用净现值（net present value, NPV）与内部收益率（internal rate of return, IRR）作为评价指标。结果显示，碳信用额度销售收入未对净现值产生显著影响，但在动物日粮中添加1.5%与3%的硝酸钙均具备经济可行性：相较于对照组日粮（R$6.13/头·日），两种添加方案分别将日粮成本降至R$5.89/头·日与R$5.81/头·日，同时助力温室气体减排。综上，硝酸钙添加饲喂不仅可减少甲烷生成，还能有效降低养殖活动的可变成本。