32. Cattle Preferential Intake of Seaweed Supplementation and Effects on Methane Emissions.

Abstract Pacific Dulse, or Dulse (Devaleraea mollis), a fast-growing red macroalga, has emerged as a potential CH4 mitigator. However, information on Dulse supplementation for cattle is limited; the effects on palatability and CH4 emissions have not been investigated. Therefore, the objective of this study was to evaluate the preferential intake of cattle offered Dulse supplementation mixed with dry distiller’s grains (DDG) at different concentrations. Ten mature cows (Angus x Hereford, 501 ± 12 kg) were enrolled in the study. Body weight (BW) was collected before (d-7), at the beginning (d0), and at the end of the supplementation (d21), and a week after the end of the supplementation (d28). Methane emissions were measured using the Greenfeed Pasture System for one week before supplementation (d-7 to 0), and for one week after the supplementation (d21 to 28). During CH4 measurement, cows were maintained as a group in dry lot pens and had ad libitum access to alfalfa-meadow hay mix (12% CP and 59% TDN). During the supplementation phase (d0 to 21), cows were moved to individual dry lot pens and were limited fed 8 kg of the hay mix. Every morning, each cow was offered three portions of DDG (226g) fortified with Dulse at three different concentrations (0.25, 0.50, and 1% of total DMI). Cows had free and simultaneous access to the fortified supplements for 4h before the hay feeding. Supplement refusals were weighed daily after the 4h period to determine preferential intake of the supplement. Preliminary data were analyzed using a MIXED procedure of SAS with time (pre- and post-supplementation) as a fixed effect and cow as the experimental unit. As expected, with the adopted limited feeding strategy, cows fully consumed the daily hay. No preferences were observed for any of the Dulse concentrations used to fortify the DDG supplement; cows consumed all the supplement offered, resulting in a daily intake of 150g of Dulse. Regardless of the limited feeding strategy, cows had greater BW at the end of the supplementation phase (P < 0.01; 501 vs. 519) and showed a trend toward a 6% reduction in CH4 emissions following supplementation (P = 0.09; 181 vs. 170 ± 6 g/cow daily). A day effect was observed in the CH4 collection periods, pre- and post-supplementation (P £ 0.01). Before supplementation, the greatest values were observed on d-6 to d-4, while the lowest were observed on d-7 and d-2 (P < 0.05). Post-supplementation, the greatest values were observed on d21 to 23, while the lowest were observed on d24 to 27 (P < 0.05). These preliminary results indicate that Dulse supplementation was readily accepted by cattle, showing potential to reduce enteric CH4 emissions, warranting further investigation under longer supplementation periods and larger sample sizes.