An increase in dietary lipid content from different forms of double-low rapeseed reduces enteric methane emission in Datong yaks on the Qinghai-Tibetan Plateau

Enteric methane (CH₄) emission in cattle generally decreases by approximately 1 g/g dry matter intake (DMI) with an increase in dietary lipids of 10 g/kg dry matter (DM). The effect of dietary lipids on CH₄ emission in yaks has not been reported and is the subject of this study. Four Datong yaks were used in a 4 × 4 Latin-square design in which the four treatments included restricted intakes of double-low rapeseed differing in form and lipid (ether extract—EE) content: (a) rapeseed meal (EE 32.6 g/kg DM); (b) rapeseed meal and rapeseed cake (EE 45.8 g/kg DM); (c) rapeseed meal and whole cracked rapeseed (EE 54.5 g/kg DM) and (d) rapeseed meal and rapeseed oil (EE 62.7 g/kg DM). The digestibility of feed components did not differ among treatments. The ruminal total volatile fatty acids (p =.082) and acetic acid (p =.062) concentrations tended to be lowest in yaks consuming the diet with highest lipid content. In addition, CH₄ production was lowest in this group (p =.004), and declined by 1.75 g/g DMI per 10 g/kg DM reduction in dietary lipid content, a rate substantially faster than in cattle.