Effects of Different Dietary Protein Source Combinations and Feeding Strategies on the Growth, Digestion, Intestine and Liver Health, and Organoleptic Quality of Large Yellow Croaker (Larimichthys crocea)

The present study investigated the effects of varying protein source combinations and feeding strategies on the growth, health and organoleptic quality of the large yellow croaker (Larimichthys crocea). Three iso-nitrogenous and iso-lipidic diets were formulated. The control diet was made with 62% fish meal (FM). The other two experimental diets were formulated by replacing 45% FM with 22.5% mealworm (TM) and 22.5% cottonseed protein concentrate (CPC), or with 22.5% TM and 22.5% Clostridium autoethanogenum protein (CAP), respectively. The three kinds of diet were named as A1, A2 and A3, respectively. Five groups of large yellow croaker were fed with two different strategies: the first three groups were continuously fed with A1, A2 and A3 diets, respectively. The fourth group was alternately fed with A1 and A2 diet every 5 days. The fifth group was alternately fed with A1 and A3 diet every 5 days. The five groups were named D1, D2, D3, D1-2 and D1-3, respectively. Results showed that D2 and D3 groups exhibited significantly lower weight gain rate (WGR) and higher feed conversion ratios (FCR) compared to the D1 group. The D1-2 and D1-3 groups exhibited improved WGR and significantly reduced FCR compared to the D2 and D3 groups. The A2 and A3 diets significantly suppressed digestive enzymes’ activities compared to A1, whereas alternate-feeding groups significantly enhanced the enzyme activities. Compared to the D1 group, D2 and D3 groups significantly downregulated mRNA expression levels of intestinal anti-inflammatory cytokines and upregulated the expression of pro-inflammatory mediators. The anti-inflammatory abilities in the D1-2 and D1-3 groups were significantly higher than those in the D2 and D3 groups. Additionally, diets containing TM+CAP and TM+CPC protein sources enhanced ventral redness and yellowness indices. Considering the growth, digestion, immunity and organoleptic quality of large yellow croaker, it is recommended to replace up to 45% of FM with TM+CPC and use an alternate-feeding strategy.