Comparing enteric methane emissions predicted from different equations based on milk fatty acid profile of dairy cows

Nowadays the livestock sector is blamed by public opinion for its contribution to the GreenHouse Gas Emissions. This study aimed to test different equations proposed in literature to predict enteric methane emissions (EME) of dairy cows from milk fatty acid (FA) profile. A database composed by milk production, composition, and FA profile of 992 dairy cows classified according to days in milk (DIM), parity order (PO), and 4 dairy systems, was used to compare EME values obtained from 21 equations proposed in literature. A mixed model was used to evaluate the effect of DIM, PO, and dairy system on EME expressed in term of intensity (16.05 ± 2.76, g/kg of milk), yield (20.63 ± 2.26, g/kg of dry matter intake), and daily production (385.43 ± 68.21, g/day). EME predicted by different equations were not correlated, except for 2 cases. EME predicted by 19 equations were significantly influenced by DIM and 13 by PO. Farming system showed significant differences in EME data (17 equations), especially comparing modern and traditional farms. New EME predicting equations based on milk yield and composition and also the maintenance requirements of dairy cows are needed.