The effect of a water-based delivery of an Ascophyllum nodosum extract on nitrogen balance, milk production and methane output in mid-late lactation dairy cows

This study evaluated the effects of an Ascophyllum nodosum (ASC) extract delivered via a water-based system to mid-late lactation dairy cows on nitrogen (N) balance, milk production and composition, ruminal fermentation and methane (CH 4 ) emissions.Nine multiparous mid-late lactation dairy cows (179 27.6 DIM; 553 50.1 kg BW; 27.1 5.82 kg milk yield) were used in a replicated 3 3 Latin square experiment consisting of 3 21-d (d) periods.Cows were randomly assigned to 1 of 3 dietary treatments consisting of a partial mixed ration (PMR) supplemented with an ASC extract at 0 g/d (CON), 157 g/d (LO) or 315 g/d (HI).The ASC extract was automatically dispensed into individual drinking troughs via a computerized water-based delivery system that evenly distributed the target dose over a 24-h (h) period.Cows had ad libitum access to the PMR, composed of grass silage and soybean meal, and were offered 3.54 kg DM of supplementary concentrate daily in the milking parlor and via the GreenFeed Emission Monitoring (GEM) unit, where CH 4 emissions were recorded.Each period included 16 d of dietary acclimatization followed by 5 d of measurements in individual metabolism stalls.Water intake, DMI, milk production and composition, and CH 4 emissions, milk, fecal and urine N outputs did not differ between treatments.However, total VFA concentrations were greater for HI cows relative to CON cows.In addition, urinary N output was higher for LO cows relative to CON and HI cows.In conclusion, this study showed that an ASC extract can be delivered via a water-based system without negatively impacting animal performance, however, improvements in N utilization or reductions in CH 4 emissions were not evident.