Effects of Calcium Salts of Fatty Acids on Lactation, Rumen Fermentation, and Methane Emission in Dairy Cows

We investigated the effects of supplementing lactating cows with 1% pellets of calcium salts of fatty acids (CSFAS) rich in unsaturated fatty acids on dry matter intake (DMI), milk yield, ruminal fermentation, estimated methane (CH₄) emissions, and plasma metabolites in lactating cows. Ten lactating Holstein cows were used in a 2 × 2 crossover design with two dietary treatments: with (FA treatment) or without (CON treatment) CSFAs. The cows were fed an experimental partial mixed ration (PMR) ad libitum plus 0.9 kg dry matter (DM)/day of concentrates at milking. The DMI of cows in the FA treatment (21.8 kg/day) tended to be higher (p < 0.10) than that of cows in the CON treatment (21.2 kg/day). Dietary treatment did not affect milk yield or milk fat, protein, or lactose concentrations. The ruminal propionic acid proportion of the FA treatment was significantly higher (p < 0.05) than in the CON treatment. The ruminal nonglucogenic/glucogenic short-chain fatty acid ratio in the FA treatment was significantly lower (p < 0.05) than in the CON treatment. The estimated CH₄ emissions per DMI of the FA treatment, measured using the sniffer method, tended to be lower (p < 0.10) than those of the CON treatment.