Conventional animal feeds significantly contribute to greenhouse gas emissions. At the same time, commercial macroalgae farming struggles in many areas due to the paucity of scalable markets. Cultivated macroalgae offer a promising alternative to land-based ingredients, due to their rapid growth and minimal environmental impact (requiring no land area, fresh water or exogenous fertilizer, and absorbing CO2 and excess nutrients). However, their complex polysaccharides render them largely indigestible by most animals. Herbivorous fish, by contrast, thrive on macroalgal diets, as their microbial consortia in the GI tract are able to deconstruct these polysaccharides into smaller, more digestible sugars and fatty acids. We have co-opted these consortia in vitro to produce, PDMA (Partially Deconstructed Macroalgae). Using PDMA for aquaculture and terrestrial ag feeds could provide a commercial driver for expanded macroalgae farming and contribute to mitigating the 7.1 gigaton of CO2 – equivalent emissions produced by terrestrial livestock annually.
This presentation reviews results of feed trials in a range of species – tilapia, chickens, salmon and shrimp - using PDMA derived from two tropical red macroalgae species (Agardhiella subulata and Halymenia hawaiiana), with microbiome from chubs (aka drummer, rudderfish; Kyphosus vaigiensis). Growth rates and feed conversion efficiencies, and measures of physiological fitness were not significantly different from animals fed control diets. Feed consumption was greater in PDMA-fed animals, in some instances.
PDMA can provide a scalable, cost-effective, and environmentally friendly alternative to traditional feed ingredients, with the potential to significantly reduce greenhouse gas emissions associated with animal agriculture and provide economic incentives for expansion of macroalgae farming.