Influence of a Blend of Dietary Essential Amino Acids on Growth, Enzymatic Activity, and Intestinal Histology of Blue Discus

Abstract

Symphysodon aequifasciatus is a fish with a disk-shaped body and bright colors, important characteristics of ornamental fish. We evaluated amino acid supplementation strategies to reduce crude protein in the diet for evaluation of performance, the content of digestive enzymes, liver metabolism, and intestinal histopathology. A total of 180 fish were randomly distributed in 12 separate 50 L glass aquariums, consisting of a completely randomized design with four treatments (DC - Control diet with 34.4% crude protein; DL - Control diet plus 1% of lysine; DEAA - Control diet plus 1% free essential amino acids (threonine, phenylalanine, leucine, valine, arginine, and tryptophan); and DHP - Diet with a high level of crude protein 48.4%), three repetitions, lasting 60 days. The use of DL and DEAA diets resulted in higher intestinal villus height and higher zootechnical performance. The use of DL diet increased alkaline phosphatase and digestive amylase activity. The use of DHP diets promotes severe liver changes due to increased activity of Alanine aminotraserase. Therefore, it was possible to observe that the use of amino acids can supply the nutritional need of blue discus. Supplementation of diets with AAs allows the reduction of dietary protein, which is a strategy for feeding management.

Evaluation of commercial and experimental grower diets for use in intensive culture of Symphysodon aequifasciatus

“…The best growth rates were observed in fish fed the BH + DD diet, this result was also reported by (Wen et al 2018), who combined a wet diet with and hearts (1: 1) and found them to be good growth promoters for S. aequifasciatus. The presence of free amino acids in the diet stimulates feeding chemoreceptors (Santos et al 2021, Camilo et al 2021. In a study with larvae of Piaractus mesopotamicus it was observed that the use of water from the hatching of brine shrimp stimulated the behavior of capturing food, these results being attributed to the presence of dissolved substances (Tesser e Portella 2006).…”