Efforts to optimize plant-based diets continue to be a key area in aquaculture nutrition research. Among traditional and novel protein feedstuffs with potential for use in aquafeeds is industrial hemp. H empseed meal (HSM) is rich in protein and lipids and might complement other protein sources in feeds for farmed aquatic animals. Nevertheless, information on the nutritional value of HSM for aquatic animals remains limited.
A digestibility trial was conducted to assess the nutriti onal value of two commercially available HSMs for Pacific white shrimp (Litopenaeus vannamei ). Four experimental diets w ere formulated by blending equal portions of a reference diet ( REF; 35% crude protein, 10% lipid) mixture with each of three test ingredients: HSM-P30 (35% CP and 20% lipid), HSM-P50 (45% CP and 23% lipid), and conventional soybean meal (CSBM) at a 70:30 ratio (dry matter basis). Each experimental diet was randomly assigned to four groups of twelve shrimp (10±1.0 g/shrimp) stocked in 16, 110-L glass aquaria operating as a recirculating aquaculture system. Water quality parameters were maintained within acceptable ranges for the shrimp. Shrimp in each aquarium were fed four times daily. Fecal matter w as collected four times throughout the day, discarding the first collection to reduce the effect of coprophagy and intake of other material other than feed, overnight. T o determine the apparent digestibility coefficients (ADCs) for crude protein, energy, and amino acids ~ 0.3% yttrium trioxide (Y2O3) was used in diet as an indicator.
Based on our results (Table 1), the CSBM and HSM-P50 diets displayed higher ADC for crude protein compared to REF and HSM-P30, while lower ADC for energy was observed in both HSM diets compared to REF and CSBM (P<0.05). For the test ingredients, higher ADC for crude protein was found in CSBM and HSM-P50 compared to HSM-P30. The highest ADC for energy was found in CSBM, followed by HSM-P50 and HSM-P30 (P< 0.05). The test ingredients also differed in terms of amino acid availability, which will be presented. Based on our findings, the HSM proteins are well digested by the Pacific white shrimp, while the lower ADCs for energy in both HSMs compared to CSBM might be due to higher fiber content in the former . Overall, our results indicate that HSM can be a good complementary source of nutrients and energy in shrimp feeds.