FEED ADDITIVES ▶▶▶
Mitigating methane production in the rumen
Several feeding strategies can be adopted to reduce methane production in the rumen. In this article, however, the focus is on the use of fat supplements in the animal’s diet.
BY DR SALAH H. ESMAIL, PHD M
When adding rapeseed oil, it was shown that methane pro- duction de- creased by 7.3% in cattle fed with corn silage or grass silage.
ethane, a product of rumen fermentation which is belched by ruminants, inhibits the nor- mal functioning of microbial enzymes and im- pairs rumen fermentation. It can also result in a
loss of dietary energy which could otherwise be used by ani- mals for productive purposes. A 20% reduction in methane emission could allow growing cattle to gain an additional 75 g/d of weight. In lactating cows, a 20% reduction in meth- ane emissions represents the same amount of energy needed to synthesize 0.6 kg/d of milk. Revenue generated from in- creased growth rates and milk yield could partially offset the cost of methane mitigation.
Mode of action of fat Supplementing diets with fats and oils reduces enteric meth- ane emissions. Reductions greater than 40% have been
achieved, but reductions of 10 to 25% are more commonly reported. Incorporating fat in the diet as an energy source lowers the carbohydrate content, which is the substrate for methane formation. Fats also reduce the number of protozoa in the rumen, many of which are physically associated with the methanogens. However, the effects of fat on methane production are not limited to those mediated via the rumen protozoa. Fats have also been shown to inhibit methanogen- esis, even in the absence of rumen protozoa. This may be due to the toxicity of long-chain fatty acids to methanogenic bac- teria, and to the fact that they typically result in a reduction in the digestibility of cell wall carbohydrates, leading to reduced production of acetate and an increased propionate to acetate + butyrate ratio, which in turn reduces the production of hydrogen and thus methane.
Effects of using different fat sources In studies examining the effect of fats on methane emission, coconut oil has frequently been used, as its fatty acid concen- tration is different from that of all other vegetable oils (i.e. it contains large amounts medium-chain fatty acids, which are particularly effective in reducing methane production). Coco- nut oil can reduce methane production by up to 70% without affecting dry matter intake, digestibility, and the production and quality of milk when added to the ration at 250 g per cow per day. In sheep feeding trials, it was determined that 25 g/kg of coconut oil reduces methane production, meth- anogen bacteria, and protozoa without affecting the sheep’s performance. The use of coconut oil above the recommended levels may, however, reduce the performance of both cattle and sheep and also make feeding programmes uneconomical due to its high cost.
It has been shown that the use of polyunsaturated fatty acids, especially from linseed, to reduce rumen methanogenesis may be a practical abatement technology for ruminant pro- duction. The use of products based on linseed is interesting due to the simultaneous enhancement of the nutritional val- ue of milk and ruminant meat, provided that the linseed does not reduce overall fermentation and thus does not impair
22 ▶ ALL ABOUT FEED | Volume 28, No. 4, 2020
PHOTO: SHUTTERSTOCK
PHOTO: MARK PASVEER
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