Abstract
Peanut (Arachis hypogaea) is mainly grown for oil extraction and the remaining oil-free seed referred as peanut meal (PM) leaves with high protein content which can be a possible substitute for fishmeal in aqua-diets. This study evaluates the suitability of three types of processed peanut seeds, namely untreated PM (UPM), fermented PM (FPM), and germinated PM (GPM) from peanut seeds to replace fishmeal in barramundi (Lates calcarifer) diets cultured under a commercial production environment. Nine formulated diets having 3 inclusion levels from the 3 different peanuts (15%, 30% and 60% fishmeal replacement) were evaluated against a control without PM. The performance of various types and levels of PMs was assessed by examining the growth, gut and liver condition and survival of fish after eight weeks of feeding the test diets. The immunological responses of juvenile barramundi were assessed by exposing the fish to the hypoxic conditions for 4 hours. The results showed that fermentation and germination significantly (P<0.05) reduced the tannins and alkaloid contents in the PMs. The fish fed 15% GPM diet grew faster and had higher survival than fish fed control diet, while fish fed diet including 60% GPM showed a significant reduction in growth and survival, and an increase in food conversion rate (FCR). FPM and UPM at any inclusion levels did not alter the growth, survival and FCR. Histology analysis revealed that fish fed 60% GPM and UPM showed higher amount of lipid droplets in liver, myodigeneration in fish muscle and a decrease number of acidic mucins in distal gut compare to all other test diets. Stress caused by reduced dissolved oxygen did not change the sodium, potassium, chlorides and alanine aminotransferase concentrations of plasma of fish fed any diet. However, the stress did increase plasma cortisol significantly (P<0.05) in fish fed 60% GPM, 30% and 60% UPM diets. These results suggest that the PMs can partly replace the fishmeal in juvenile barramundi diet and the processing further improves the PMs quality by reducing its antinutritional factors which in turn can increase either its inclusion level in the barramundi diets or improved growth and health status of the species.
Highlights
The increase in fish production through aquaculture has been accompanied by rapid growth of aquafeed production
Most peanuts are used for oil extraction for human consumption [16], and the rest, peanut meal (PM) as a rich protein source can be an ideal ingredient in aqua-feed
Fermentation and germination resulted in lower concentration (P
Summary
The increase in fish production through aquaculture has been accompanied by rapid growth of aquafeed production. The failure to use higher inclusion level is due to the presence of higher levels of undesirable antinutritional factors (ANFs) [12] that adversely influence the fish growth and health status of fish Legumes such as lupins and soybeans contain large amounts of ANFs as soluble and insoluble non-starch polysaccharides, oligosaccharides, phytates, and tannins. Most peanuts are used for oil extraction for human consumption [16], and the rest, peanut meal (PM) as a rich protein source can be an ideal ingredient in aqua-feed This PM, as other plant rich protein sources, contains ANFs such as tannins, trypsin and amylase inhibitors [17], which can have adverse effects on the fish. This study assessed the processed peanut meals (PMs) as a potential protein source to replace fishmeal in juvenile barramundi diets by evaluating growth, gut and liver health, and immunological indices of fish challenging to an acute hypoxic condition
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