Evaluation of the digestibility and effects on key performance indicators of mushroom-derived alternative protein sources in aquafeeds for rainbow trout (Oncorhynchus mykiss)

The mushroom industry generates by-products often classified as waste, making waste management a significant concern. To address this challenge and meet the growing demand for alternative protein sources in aquafeeds, this study evaluated the in vitro and in vivo digestibility of mushroom meals derived from three commercially cultivated species: Agaricus bisporus (AB), Lentinula edodes (LE), and Pleurotus ostreatus (PO) in rainbow trout ( Oncorhynchus mykiss ), as well as key performance indicators associated to growth, feed efficiency and body condition. In vitro digestibility was evaluated using semi-permeable membrane bioreactors by measuring liberated amino acids, while in vivo digestibility coefficients (ADCs) and key performance indicator (KPI) analyses were determined by feeding O. mykiss with diets containing AB, LE and PO meals for 42 days. Results showed that AB meal had similar in vitro digestibility to fish meal ( p > 0.05), while LE and PO displayed intermediate and lowest digestibility values, respectively. Conversely, the in vivo ADCs of LE and PO meals was similar to the control ( p > 0.05), whereas AB meal showed the lowest ADCs. Growth performance, somatic indices, blood biochemistry, whole-body composition, and digestive enzyme activities of O. mykiss were unaffected by AB, LE and PO diets ( p > 0.05), but hepatic carbohydrate content and vacuolization increased in LE fed group ( p < 0.05). Overall, although the digestibility of the three meals differed in vitro and in vivo , their crude protein ADC values were high (diet: > 90%; ingredient: > 77%) and did not compromise O. mykiss growth or feed efficiency. Thus, mushroom by-products may serve as alternative protein ingredients for aquafeeds.