System: Dairy Cattle

Mainly applicable for: Low initial fat content of the diet (i.e. no fat-rich supplements included already), TMR systems, and zero- or low-grazing systems

Not applicable or effective for: Not applicable if in the reference situation the diet already has a 7% fat content, because extra supplementation would lead to trade-offs such as reduced DMI and fibre digestibility.

Description

Supplementing fats, oils, or free fatty acids (saturated or (poly)unsaturated) to the ration or to concentrate feed, in order to reduce the enteric methane emission in the rumen. It also delivers a high energetic source to the animal. Different types of lipid can be fed, such as coconut oil, sunflower oil, palm oil, or ingredients with a very high oil content such as crushed oilseeds. They can be applied in different forms; the so-called unprotected forms exerting an effect on rumen fermentation versus the protected forms with minimal impact and interaction with rumen fermentation. Exceeding the maximum level of usage, in particular of unprotected forms, increases dietary fat content too much and negatively impacts rumen function, fibre digestion, dry matter intake and milk production.

Mechanism of effect

Increasing the dietary lipid content reduces enteric methane emissions, mainly due to i) increased digestive efficiency, as lipids are high in energy (and low in fibres); ii) direct inhibition of methanogens, reducing their activity; iii) an effect on cell-wall degradation (to be prevented as it reduces feed efficiency), and iv) changes in the rumen fermentation profile (volatile fatty acids, and associated amount of hydrogen/methane produced) leading to less hydrogen production as substrate for methanogens. It also reduces emissions per kg product due to increased productivity. Adding lipids to a diet also leads to a lower nitrogen (N) content relative to the energy content of the diet, thereby reducing N excretion and ammonia and nitrous oxide emissions. Some lipids are associated with land use change (LUC) effects, such as palm oil or soybean oil from areas with deforestation risks.

Reference situation

Normal lipid content of the diet without inclusion of a product as fat/oil supplement, enabling fat supplementation of 3-4% of dietary dry matter as fat.

Legend

● – Small effect (<5%)	o – No effect
●● – Medium effect (5-20%)	● – Unfavourable effect
●●● – Large effect (>20%)	● – ● – Variable effect (depending on farm characteristics or way/level of implementation)

Cause of variable or unfavourable effect