Variability and potential of seaweeds as ingredients of ruminant diets: An in vitro study

Abstract

This study was designed to analyze the chemical composition and in vitro rumen fermentation of eight seaweed species (Brown: <i>Alaria esculenta, Laminaria digitata, Pelvetia canaliculata, Saccharina latissima; Red: Mastocarpus stellatus, Palmaria palmata and Porphyra sp.; Green: Cladophora rupestris</i>) collected in Norway during spring and autumn. Moreover, the in vitro ruminal fermentation of seventeen diets composed of 1:1 oat hay: concentrate, without (control diet) or including seaweeds was studied. The ash and N contents were greater (p < 0.001) in seaweeds collected during spring than in autumn, but autumn-seaweeds had greater total extractable polyphenols. Nitrogen in red and green seaweeds was greater than 2.20 and in brown seaweeds, it was lower than 1.92 g/kg DM. Degradability after 24 h of fermentation was greater in spring seaweeds than in autumn, with <i>Palmaria palmata</i> showing the greatest value and <i>Pelvetia canaliculata</i> the lowest. Seaweeds differed in their fermentation pattern, and autumn <i>Alaria esculenta, Laminaria digitata, Saccharina latissima and Palmaria palmata</i> were similar to high-starch feeds. The inclusion of seaweeds in the concentrate of a diet up to 200 g/kg concentrate produced only subtle effects on in vitro ruminal fermentation.