Effect of whole seaweed and seaweed extract on rumen fermentation, nutrient digestibility, and methane emissions of beef heifers fed a high-forage diet

The effect of the whole seaweed Ascophyllum nodosum and a seaweed extract generated from Himanthalia elongata on rumen fermentation, nutrient digestibility, and methane (CH 4 ) emissions of beef heifers fed a high-forage diet was assessed. A replicated 3 × 3 Latin square was conducted using six ruminally cannulated beef heifers fed a basal diet consisting of 52% barley silage, 44% barley straw, and 4% mineral supplement (dry matter (DM) basis). Whole A. nodosum and H. elongata extract were supplemented into the diet at 2% of dietary DM replacing equal proportions of barley silage and barley straw. There was no effect of treatment ( p ˃ 0.05) on the production of ammonia (NH 3 ), protozoa counts, total volatile fatty acids, or ruminal pH. The apparent total tract digestibility of neutral detergent fibre (NDF) and acid detergent fibre (ADF) was increased ( p ˂ 0.05) by the H. elongata extract compared to the control, but there was no effect ( p ˃ 0.05) of A. nodosum or H. elongata extract on CH 4 production (g/day) or yield (g/kg DM intake). In conclusion, neither the whole A. nodosum nor the H. elongata extract demonstrated anti-methanogenic activity in a high-forage diet.