Expanding the menu for New Zealand farmed abalone: dietary inclusion of insect meal and grape marc (effects on gastrointestinal microbiome, digestive morphology, and muscle metabolome)

Limited supply of sustainable feed ingredients is a significant concern for future aquaculture practices. Alternative ingredients, such as insect meal and grape marc, are suitable for aquaculture nutrition due to their nutritional profile and more sustainable production methods. This study assessed the effect of dietary insect meal and grape marc on gut microbial composition, digestive system morphology, and muscle metabolome of Haliotis iris. Juvenile abalone were fed four encapsulated experimental diets with varying levels of insect meal/grape marc and a commercial feed for 165 days in a commercial farm. The gut health of abalone was evaluated through histopathology, and 16S rRNA amplicon libraries through Illumina MiSeq sequencing. The abalone metabolome was evaluated through gas chromatography-mass spectrometry (GC-MS). Results showed that animals had good intestinal condition across all dietary treatments. Microbiome analysis revealed increased relative abundances of bacteria (Firmicutes and Fusobacterium) associated with the breakdown of polysaccharides in diets including insect meal and grape marc. Metabolite profile variations indicate that the inclusion of insect meal and grape marc favoured fatty acid metabolism and amino acid catabolism, respectively. This study provides foundation to produce more sustainable feeds including insect meal and grape marc without affecting the gut and overall health of abalone.

Keywords: Abalone; Microbiome; Histology; Metabolomics; Insect meal; Grape marc; Gut health