Effect of dl-malic acid supplementation on feed intake, methane emissions, and performance of lactating dairy cows at pasture

The objective of this study was to determine the effect of dietary dl-malic acid (MA) supplementation on feed intake, methane (CH4) emissions, and performance of mid lactation Holstein-Friesian cows at pasture. Twenty-four (6 primiparous and 18 multiparous) mid- to late-lactation cows (206 ± 65 d in milk) grazing a mixed-species grass sward were blocked on parity, days in milk, and pretrial milk yield, and randomly allocated within block to 1 of 2 dietary treatments offered twice daily at milking in 2 equal portions (6 kg/d in total): a control concentrate (0 g/d of MA) and a concentrate supplemented with MA (480 g/d of MA) over a 6-wk period. Cows were allowed a 3-wk acclimation period followed by a 5-d CH4 measurement period. Enteric CH4 emissions were estimated using the sulfur hexafluoride tracer gas technique, and herbage intake was measured using the n-alkane technique. Dietary supplementation with MA did not affect voluntary intake of herbage or total dry matter intake, body weight gain, milk yield, fat-corrected milk yield, or daily CH4 production. These results suggest that there is little benefit to be gained from the dietary supplementation of dairy cows at pasture with MA at least within the inclusion rates used in this study.