Maccarana Laura, Cattani Mirko, Tagliapietra Franco, Bailoni Lucia, Schiavon Stefano
Department of Comparative Biomedicine and Food Science (BCA), University of Padova, Viale dell'Università 16, 35020 Legnaro (PD), Italy.
Department of Agronomy, Food, Natural resources, Animals and Environment (DAFNAE), University of Padova, Viale dell'Università 16, 35020 Legnaro (PD), Italy.
J Anim Sci Biotechnol. 2016 Sep 17;7:54. doi: 10.1186/s40104-016-0109-5. eCollection 2016.
Modification of chemical composition of diets fed to dairy cows might be a good strategy to reduce methane (CH4) production in the rumen. Notable reductions of CH4 production compared to conventional high-roughages rations were more frequently observed for very concentrated diets or when fat supplements were used. In these cases, the reduction in the gas emission was mainly a consequence of an overall impairment of rumen function with a reduction of fiber digestibility. These strategies do not always comply with feeding standards used in intensive dairy farms and they are usually not applied owing to the risks of negative health and economic consequences. Thus, the present study evaluated the effects of seven commercial diets with contents of neutral detergent fiber (NDF), protein and lipids ranging 325 to 435 g/kg DM, 115 to 194 g/kg DM, and 26 to 61 g/kg DM, respectively, on in vitro degradability, gas (GP), and CH4 production.
In this experiment, changes in the dietary content of NDF, crude protein (CP) and lipids were always obtained at the expense or in favor of starch. A decreased of the dietary NDF content increased NDF (NDFd) and true DM (TDMd) degradability, and increased CH4 production per g of incubated DM (P < 0.001), but not that per g of TDMd. An increase of the dietary CP level did not change in vitro NDFd and TDMd, decreased GP per g of incubated DM (P < 0.001), but CH4 production per g of TDMd was not affected. An increased dietary lipid content reduced NDFd, TDMd, and GP per g of incubated DM, but it had no consequence on CH4 production per g of TDMd.
It was concluded that, under commercial conditions, changes in dietary composition would produce small or negligible alterations of CH4 production per unit of TDMd, but greater differences in GP and CH4 production would be expected when these amounts are expressed per unit of DM intake. The use of TDMd as a standardizing parameter is proposed to account for possible difference in DM intake and productivity.
改变奶牛日粮的化学成分可能是减少瘤胃甲烷（CH4）产生的一种有效策略。与传统的高粗饲料日粮相比，在非常浓缩的日粮或使用脂肪补充剂时，更常观察到CH4产生量显著减少。在这些情况下，气体排放的减少主要是瘤胃功能整体受损以及纤维消化率降低的结果。这些策略并不总是符合集约化奶牛场使用的饲养标准，而且由于存在负面健康和经济后果的风险，通常不被采用。因此，本研究评估了七种商业日粮（中性洗涤纤维（NDF）、蛋白质和脂质含量分别为325至435 g/kg干物质、115至194 g/kg干物质和26至61 g/kg干物质）对体外降解率、气体（GP）和CH4产生的影响。
在本实验中，日粮中NDF、粗蛋白（CP）和脂质含量的变化总是以牺牲或有利于淀粉为代价。日粮NDF含量的降低增加了NDF（NDFd）和真干物质（TDMd）的降解率，并且每克培养干物质的CH4产生量增加（P < 0.001），但每克TDMd的CH4产生量没有增加。日粮CP水平的提高并未改变体外NDFd和TDMd，每克培养干物质的GP降低（P < 0.001），但每克TDMd的CH4产生量未受影响。日粮脂质含量的增加降低了每克培养干物质的NDFd、TDMd和GP，但对每克TDMd的CH4产生量没有影响。
得出的结论是，在商业条件下，日粮组成的变化将使每单位TDMd的CH4产生量产生微小或可忽略不计的变化，但当这些量以每单位干物质摄入量表示时，预计GP和CH4产生量会有更大差异。建议使用TDMd作为标准化参数，以考虑干物质摄入量和生产力的可能差异。
