The effect of increasing canola oil and soybean oil addition to beef cattle rations based on corn silage and barley grain on the <i>in vitro</i> ruminal gas production and rumen fermentation

Abstract The purpose of the current experiment was to determine the effects of ruminal fermentation parameters of the additions of canola or soybean oils at different rates (4, 8 and 12%) to beef cattle total mix rations (TMR), based on corn silage and barley grain. The addition of 4% soybean oil to TMR positively affected in vitro gas production, net energy lactation (NE L ), metabolic energy (ME), and organic matter digestion (OMd). The additions of 8% and 12% of soybean oil to TMR linearly decreased ME, NE L and OMd ( p &lt; 0.05). The additions of 4, 8 and 12% canola oil to the TMR linearly decreased the in vitro gas production and estimated fermentation values (ME, NE L and OMd) ( p &lt; 0.05). All doses of soybean or canola oils in TMR reduced the molarities of total short‐chain fatty acids (tSFCA), acetic (AA), butyric (BA), propionic (PA), valeric (VA), iso‐valeric (IVA) and iso‐butyric acids (IBA) for in vitro fermentation fluid ( p &lt; 0.05). There was a negative correlation between the increasing dietary stearic, oleic and linoleic acid and the end‐products of in vitro rumen fermentation. However, increasing dietary α‐linolenic acids had no adverse effect on in vitro ruminal fermentation end‐products. As a result, 4% addition of the soybean oil, which included a higher rate of α‐linolenic acid and saturated fatty acids and a lower rate of oleic, linoleic acids according to those of canola oil, to the TMR positively affected in vitro ruminal fermentation. In addition, the ≥8% addition of canola or soybean oil adversely affected the in vitro fermentation values.