The scarcity of fish meal (FM) and the rising cost of soybean meal (SBM) are compelling reasons to explore new, sustainable protein sources for aquafeed. Hemp heart meal (HHM) products are high-quality plant-based proteins that offer a favorable essential amino acid profile and a well-balanced omega-6 to omega-3 fatty acid ratio, a property not commonly found in other plant proteins. This study evaluated the apparent digestibility coefficients (ADCs) of dry matter, crude protein, crude lipid, energy, and amino acids of two HHMs and compared them to conventional protein sources in juvenile rainbow trout (Oncorhynchus mykiss).
A seven-week feeding trial was conducted with 400 trout distributed across 20 180-L tanks operating as a recirculating aquaculture system. The trout were fed five formulated diets, including a reference diet and test diets containing 70% reference diet and 30% test ingredient mixtures. The four test ingredients were defatted HHM (DHM), full-fat HHM (FHM), FM and SBM. Each diet contained yttrium trioxide as an inert marker for ADC determinations and was randomly assigned to four replicate tanks. Fecal samples were collected by stripping once a week, dried and kept frozen for subsequent chemical analyses.
The results (Table 1) showed no significant differences (P>0.05) in dry matter and lipid ADCs among the test ingredients. However, FHM exhibited significantly lower protein ADC than SBM and DHM. Regarding energy ADC, FM had the highest value followed by FHM and either SBM or DHM. Although FHM had a significantly lower energy ADC than FM, it was significantly higher than SBM and DHM.
In conclusion, HHM products are highly digestible protein feedstuffs with crude protein, crude lipid, and dry matter ADCs comparable to conventional protein sources. These findings indicate that HHM products have strong potential as protein sources for aquaculture feeds, and may contribute to more sustainable aquaculture practices. Results on diet and amino acid ADCs, and cannabinoid profiles will be presented.