In vitro evaluation of feeding North Atlantic stormtoss seaweeds on ruminal digestion

Abstract

Feeding seaweeds and macroalgal products has been shown to reduce enteric methane emission from rumen fermentation. On Prince Edward Island, Canada, stormtoss shoreweed (SHW) consists of variable seaweed proportions of Chondrus crispus (Irish moss; IM), Laminaria longicruris, and Fucus vesiculosus. The impact of invasion by Furcellaria spp. (FF) and its increasing proportion in SHW harvests on feeding value has not been evaluated. The aim of this study was to determine effects of feeding SHW on ruminal fermentation and methane production. Effects were assessed in vitro using continuous culture with pooled rumen inocula from Holstein cows. In vitro cultures were maintained on 30 g day−1 of the dietary dry matter (DM) fed to donor cows and were supplemented with FF or IM at 0.14, or SHW at 0.14 (SHW1), 0.28 (SHW2), or 0.56 (SHW3) g DM day−1. There was little change in pH, total volatile fatty acids, or the acetate/propionate ratio due to seaweeds. The SHW mix and component seaweeds reduced the post-fermentation level of NH3-N suggesting decreased deamination of dietary and microbial amino acids. Methane emission was reduced on average 12 % with seaweeds and maximally by 16 % with SHW2. Reduction in methane production was not induced by impaired organic matter (OM) digestibility which averaged 46 %. North Atlantic SHW has potential based on in vitro screening at these doses to be fed to ruminants with beneficial effects on methane production at little cost to dietary digestibility.