Inclusion of Red Macroalgae (Asparagopsis taxiformis) in Dairy Cow Diets Modulates Feed Intake, Chewing Activity and Estimated Saliva Secretion

SIMPLE SUMMARY: Here, we studied how Asparagopsis taxiformis—an emerging ruminant feed additive with methane inhibitory effect—affected the feed intake of early lactating dairy cows given free access to total mixed ration and drinking water. Eating–rumination behaviour was recorded continuously for 11 days, using electronic sensors, on 15 lactating Norwegian Red dairy cows fed diets with graded levels (0, 0.125 and 0.25% on an organic matter basis) of the macroalgae. Our results indicated that the macroalgae reduced feed intake through reduced feed intake rate, and increased eating and chewing indices. Inclusion of the macroalgae increased the estimated saliva production per unit dry matter intake. To our knowledge, this is the first documentation on the eating–rumination behaviour of dairy cows given access to a diet containing this novel ingredient. Alternative modes of delivery of the ingredient, in contrast to what is commonly used now (i.e., blending it with a water–molasses mixture) is envisaged. ABSTRACT: The current study assessed the effects of red macroalgae Asparagopsis taxiformis (AT)—included as an enteric methane inhibitor—in dairy cow diets on feed intake and eating–rumination behaviour. Fifteen early lactating Norwegian Red dairy cows were offered ad libitum access to drinking water and a total mixed ration (TMR) composed of 35% concentrate feed and 65% grass silage on a dry matter (DM) basis. The experiment lasted for 74 days with the first 22 days on a common diet used as the covariate period. At the end of the covariate period, the cows were randomly allocated into one of three dietary treatments: namely, 0% AT (control), 0.125% AT and 0.25% AT in the TMR. The TMR was offered in individual feed troughs with AT blended in a 400 g (w/w) water–molasses mixture. Eating–rumination behaviour was recorded for 11 days using RumiWatchSystem after feeding the experimental diets for 30 days. The 0.25% AT inclusion significantly reduced the DM intake (DMI). Time (min/d) spent on eating and eating in a head-down position increased with the increasing AT level in the diet, whereas rumination time was not affected. The greater time spent on eating head-down with the 0.25% AT group resulted in a significantly higher chewing index (min/kg DMI). Estimated saliva production per unit DMI (L/kg DMI, SE) increased from 10.9 (0.4) in the control to 11.3 (0.3) and 13.0 (0.3) in the 0.125% and 0.25% AT groups, respectively. This aligned with the measured ruminal fluid pH (6.09, 6.14, and 6.37 in the control, 0.125% AT and 0.25% AT groups, respectively). In conclusion, either the level of the water–molasses mixture used was not sufficient to mask the taste of AT, or the cows used it as a cue to sort out the AT. Studies with relatively larger numbers of animals and longer adaptation periods than what we used here, with varied modes of delivery of the seaweed may provide novel strategies for administering the additive in ruminant diets.