Abstract：
No single enteric CH4 mitigating strategy has been consistently effective or is readily applicable to ruminants in grassland systems. When CH4 mitigating strategies are effective under grazing conditions, mitigation is mild to moderate at best. A study was conducted to evaluate the potential of combining two CH4 mitigation strategies deemed feasible to apply in grazing dairy cows, the methanogenesis inhibitor 3-nitrooxypropanol additive (3-NOP) and cottonseed supplementation (CTS), seeking to enhance their individual CH4 mitigating potential. Forty-eight dairy cows were evaluated in a continuous grazing study and supplemented with either a starch-based concentrate (STA) or one that contained cottonseeds (1.75 kg DM/d; CTS), and with either 19 g/d of 10% 3-NOP (Bovaer®) or the additive\'s carrier (placebo), in a 2 × 2 factorial arrangement of treatments. Treatments were supplied mixed with a concentrate supplement (5 kg/d as fed) and offered in two equal rations at milking. Methane emissions were measured on weeks 4 and 8 using the sulphur hexafluoride tracer gas technique over a 5-d period. The 3-NOP and CTS treatments tended to interact on absolute CH4 such that 3-NOP decreased CH4 by 13.4% with STA, but there was no mitigation with 3-NOP and CTS. Treatment interactions were also obtained for CH4 yield, where 3-NOP tended to decrease CH4 when supplied with STA, and tended to increase it with CTS. The increase in CH4 yield with the CTS diet was driven by a numerical decrease in DM intake. Methane intensity was not affected by the 3-NOP or CTS treatments. Total volatile fatty acids in ruminal fluid were not affected by 3-NOP supplementation, but a reduction in acetate and an increase in propionate proportion occurred, resulting in decreased acetate: propionate. The 3-NOP additive decreased grass intake; however, energy-corrected milk yield and milk composition were largely unaffected. Milk urea increased with 3-NOP supplementation. Combining twice daily supplementation of 3-NOP and CTS did not enhance their CH4 mitigation potential when fed to grazing dairy cows. The relatively low inhibition of CH4 production by 3-NOP compared to studies with total mixed rations may result from the mode of delivery (pulse dosed twice daily) and time gap caused by experimental handling and moving of animals to pasture after 3-NOP supplementation in the milking parlour, which could have impaired the synchrony between the additive presence in the rumen and grass intake in paddocks.
摘要：
没有单一的肠道CH4缓解策略一直有效或易于适用于草地系统中的反刍动物。当CH4缓解策略在放牧条件下有效时，缓解充其量是轻度至中度。进行了一项研究，以评估将两种被认为可行的CH4缓解策略结合在放牧奶牛中的潜力。甲烷生成抑制剂3-硝基氧丙醇添加剂（3-NOP）和棉籽补充剂（CTS），寻求增强他们个人的CH4缓解潜力。在连续放牧研究中评估了48头奶牛，并补充了淀粉基浓缩物（STA）或含有棉籽的浓缩物（1.75kgDM/d；CTS），和19g/d的10%3-NOP(Bovaer®)或添加剂载体(安慰剂),在2×2阶乘排列的处理中。将处理与浓缩物补充剂（5kg/d作为饲料）混合提供，并在挤奶时以两种相等的口粮提供。使用六氟化硫示踪气体技术在第4周和第8周测量了5天的甲烷排放量。3-NOP和CTS处理倾向于与绝对CH4相互作用，使得3-NOP与STA一起使CH4降低13.4%，但是3-NOP和CTS没有缓解。还获得了CH4产量的处理相互作用，当供应STA时，3-NOP倾向于降低CH4，并倾向于用CTS增加它。CTS饮食中CH4产量的增加是由DM摄入量的数字减少驱动的。甲烷强度不受3-NOP或CTS处理的影响。瘤胃液中的总挥发性脂肪酸不受3-NOP补充的影响，但是乙酸盐的减少和丙酸盐比例的增加，导致乙酸盐：丙酸盐减少。3-NOP添加剂减少了草的摄入量；然而，能量校正的产奶量和乳成分在很大程度上不受影响.牛奶尿素随着3-NOP的补充而增加。当饲喂放牧奶牛时，每天两次补充3-NOP和CTS并不能增强其CH4缓解潜力。与总混合口粮的研究相比，3-NOP对CH4产生的抑制作用相对较低，可能是由于分娩方式（每天两次脉冲给药）和实验处理和在3-NOP补充后将动物转移到牧场引起的时间间隔在挤奶室中，这可能会损害瘤胃中添加剂的存在与围场中草的摄入量之间的同步性。
