Romero-Perez A, Okine E K, McGinn S M, Guan L L, Oba M, Duval S M, Kindermann M, Beauchemin K A
J Anim Sci. 2015 Apr;93(4):1780-91. doi: 10.2527/jas.2014-8726.
The objective was to evaluate whether long-term addition of 3-nitrooxypropanol (NOP) to a beef cattle diet results in a sustained reduction in enteric CH4 emissions in beef cattle. Eight ruminally cannulated heifers (637 ± 16.2 kg BW) were used in a completely randomized design with 2 treatments: Control (0 g/d of NOP) and NOP (2 g/d of NOP). Treatments were mixed by hand into the total mixed ration (60% forage, DM basis) at feeding time. Feed offered was restricted to 65% of ad libitum DMI (slightly over maintenance energy intake) and provided once per day. The duration of the experiment was 146 d, including an initial 18-d covariate period without NOP use; a 112-d treatment period with NOP addition to the diet, divided into four 28-d time intervals (d 1 to 28, 29 to 56, 57 to 84, and 85 to 112); and a final 16-d recovery period without NOP use. During the covariate period and at the end of each interval and the end of the recovery period, CH4 was measured for 3 d using whole animal metabolic chambers. The concentration of VFA was measured in rumen fluid samples collected 0, 3, and 6 h after feeding, and the microbial population was evaluated using rumen samples collected 3 h after feeding on d 12 of the covariate period, d 22 of each interval within the treatment period, and d 8 of the recovery period. Average DMI for the experiment was 7.04 ± 0.27 kg. Methane emissions were reduced by 59.2% when NOP was used (9.16 vs. 22.46 g/kg DMI; P < 0.01). Total VFA concentrations were not affected (P = 0.12); however, molar proportion of acetate was reduced and that for propionate increased when NOP was added (P < 0.01), which reduced the acetate to propionate ratio (3.0 vs. 4.0; P < 0.01). The total copy number of the 16S rRNA gene of total bacteria was not affected (P = 0.50) by NOP, but the copy number of the 16S rRNA gene of methanogens was reduced (P < 0.01) and the copy number of the 18S rRNA gene of protozoa was increased (P = 0.03). The residual effect of NOP for most of the variables studied was not observed or was minimal during the recovery period. These results demonstrated that the addition of NOP to a diet for beef cattle caused a sustained decrease of methanogenesis, with no sign of adaptation, and that these effects were reversed once NOP addition was discontinued
本研究旨在评估在肉牛日粮中长期添加3-硝基氧丙醇（NOP）是否能持续减少肉牛的肠道甲烷排放。选用8头安装了瘤胃瘘管的小母牛（体重637±16.2千克），采用完全随机设计，设置2种处理：对照组（不添加NOP，0克/天）和NOP组（添加NOP，2克/天）。在喂食时，将处理剂手工混入全混合日粮（以干物质计，60%为粗饲料）中。提供的饲料限制为随意采食量的65%（略高于维持能量摄入量），每天投喂一次。实验持续146天，包括初始18天的无NOP使用的协变量期；112天的日粮添加NOP的处理期，分为四个28天的时间段（第1至28天、第29至56天、第57至84天和第85至112天）；以及最后的16天无NOP使用的恢复期。在协变量期以及每个时间段结束和恢复期结束时，使用全动物代谢室测量3天的甲烷排放量。在喂食后0、3和6小时采集瘤胃液样本，测量挥发性脂肪酸（VFA）浓度，并在协变量期第12天、处理期每个时间段的第22天以及恢复期第8天喂食后3小时采集瘤胃样本，评估微生物种群。实验期间的平均干物质采食量为7.04±0.27千克。使用NOP时，甲烷排放量降低了59.2%（分别为9.16和22.46克/千克干物质采食量；P<0.01）。总VFA浓度未受影响（P=0.12）；然而，添加NOP后，乙酸的摩尔比例降低，丙酸的摩尔比例增加（P<0.01），这降低了乙酸与丙酸的比例（分别为3.0和4.0；P<0.01）。NOP对总细菌16S rRNA基因的总拷贝数没有影响（P=0.50），但产甲烷菌的16S rRNA基因拷贝数减少（P<0.01），原生动物的18S rRNA基因拷贝数增加（P=0.03）。在恢复期，未观察到或仅观察到NOP对大多数研究变量的残留影响极小。这些结果表明，在肉牛日粮中添加NOP可使甲烷生成持续减少，且无适应迹象，一旦停止添加NOP，这些影响就会逆转。
