Effects of Dietary Plant Protein Replacement with Insect and Poultry By-Product Meals on the Liver Health and Serum Metabolites of Sea Bream (Sparus aurata) and Sea Bass (Dicentrarchus labrax)

Abstract

The liver health of Gilthead sea bream and European sea bass, fed with fish meal-free diets, including various proportions of plant proteins, as well as insect and poultry by-product meals, was investigated through biochemical and histological analyses using a new liver index (LI) formula. Four isoproteic (45% Dry Matter, DM) and isolipidic (20% DM) diets were compared, including a plant-based control diet (CV) and three other test diets, in which 40% of a plant protein-rich ingredient mixture was replaced with meals from Hermetia illucens (H40) or poultry by-product (P40) alone, or in combination (H10P30). The trials lasted 12 and 18 weeks for sea bream and sea bass, respectively. The results obtained thus far highlighted species-specific differences in the physiological response to dietary changes. In sea bream, the biochemical and histological responses suggest favorable physiological and liver health statuses, with higher serum cholesterol (CHO) and triglyceride (TAG) levels, as well as moderate hepatocyte lipid accumulation, with the H10P30 diet compared to the CV (p < 0.05). In sea bass, all diets resulted in elevated serum TAG levels and lipid accumulation in the liver, particularly in fish fed the P40 one (p < 0.05), which resulted in the highest LI, coupled with a higher frequency of severe lipid accumulation, hypertrophy, cord loss, peripheral nuclei displacement, and pyknosis. In conclusion, sea bream adapted well to the test diets, whereas sea bass exhibited altered hepatic lipid metabolism leading to incipient liver steatosis, likely due to the high lipid contents of the diets, including the insect and poultry meals. The LI formula developed in this study proved to be a reliable tool for assessing the effects of dietary changes on the liver health of sea bream and sea bass, consistent with biochemical and histological findings.

Growth, Hepatic Enzymatic Activity, and Quality of European Seabass Fed on Hermetia illucens and Poultry By-Product Meal in a Commercial Farm

“…The eviscerated weight of SSH fish was also about 10% higher than that of fish fed CG diet, resulting in relevant commercial implications. No effect on growth performance was noticed in previous experimental studies in which European seabass were fed diets containing 19.5% HIM [18], or gilthead seabream fed diets containing 32.4% HIM and 27.5% PBM [6,24,25]. Thus, the present results confirm the possible use of HIM and PBM in a plant-rich diet for marine species previously observed on an experimental scale [24,25].…”

“…Although the output of using either HIM or PBM individually is promising, in the frame of sustainable aquaculture intensification, a single protein source is unlikely to meet the essential nutritional requirements of fish and at the same time provide the best quality end-product [10]. During the last five years, the national project "SUstainable fiSH feeds INnovative ingredients-SUSHIN" funded by the AGER2 Network Foundation has evaluated the potential of different unconventional and underused ingredients, tested singly or in combination, as alternative protein sources for aquafeeds, generating new information on the environmental footprint of feeds [12], on fish growth and welfare, and on the nutritional traits of carnivorous fish species economically important for the European aquaculture [22][23][24]. In addition, results obtained under experimental conditions show that feeding gilthead seabream for 18 weeks with diets containing a negligible amount of FM and 40% plant protein replacement by PBM and HIM alone or in combination (30% and 10%, respectively) improved the zootechnical performance of fish and the nutritional characteristics of the fillets, also ensuring physiological well-being and liver health [24,25].…”

“…During the last five years, the national project "SUstainable fiSH feeds INnovative ingredients-SUSHIN" funded by the AGER2 Network Foundation has evaluated the potential of different unconventional and underused ingredients, tested singly or in combination, as alternative protein sources for aquafeeds, generating new information on the environmental footprint of feeds [12], on fish growth and welfare, and on the nutritional traits of carnivorous fish species economically important for the European aquaculture [22][23][24]. In addition, results obtained under experimental conditions show that feeding gilthead seabream for 18 weeks with diets containing a negligible amount of FM and 40% plant protein replacement by PBM and HIM alone or in combination (30% and 10%, respectively) improved the zootechnical performance of fish and the nutritional characteristics of the fillets, also ensuring physiological well-being and liver health [24,25]. Pleić et al [26] found that plant-based diets supplemented with HIM in combination with PBM resulted in the highest specific growth rates and lowest feed conversion ratios for European seabass while maintaining the nutritional value of the fillets for human consumption.…”

The Replacement of Fish Meal with Poultry By-Product Meal and Insect Exuviae: Effects on Growth Performance, Gut Health and Microbiota of the European Seabass, Dicentrarchus labrax

“…As for the present study, the histological results indicate a favorable liver health status, with a moderate accumulation of lipids in hepatocytes in all fish regardless of diet. In contrast, Donadelli et al [47] recently observed a significant accumulation of hepatocyte lipids associated with marked histological changes that were indicative of an incipient steatotic state in seabass fed a FM-free diet in which 40% of the plant protein was replaced with insect or poultry by-product. These changes appeared to be slightly attenuated when insect meal and PBM were combined to partially replace plant proteins in the diet.…”

“…The data available in the literature indicate species-specific differences in the responses to alternative protein-rich feed components. For example, the inclusion of Hermetia illucens and PBM in diets containing no FM resulted in improved gut and liver health in gilthead seabream and rainbow trout [18,24,47].…”