Evaluation of protein: lipid ratio on growth, feed efficiency, and metabolic response in juvenile yellowtail snapper Ocyurus chrysurus (Bloch, 1791)

Abstract

This study was conducted to evaluate juveniles' Ocyurus chrysurus (13.7 ± 0.45 g initial weight) to utilize lipid as an energy source on growth, feed efficiency, body composition, digestive and hepatic enzyme activities. Four diets of two protein levels (40 and 50%) with two lipid levels (6 and 12%) and 2% of digestible carbohydrates were formulated. Fish were fed for 60 days to apparent satiation at a stocking density of 10 fish per tank (100 L). Growth gain of fish fed 50% dietary protein was higher than of fish fed 40% dietary protein (P < 0.05). However, feed efficiency was significantly higher at 12 than 6% of dietary lipid. Whole-body lipid and glycogen in the liver increased dramatically with dietary lipid content-alkaline protease activity trend increased as dietary protein increased. Trypsin activity increased significantly as dietary lipid decreased, whereas chymotrypsin activity showed the opposite trend (P < 0.05). Bile salt-dependent lipase activity trend towards increasing as dietary energy decreased. Glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH), and fructose-1, 6-biphosphatase (FBPase) significantly increased with increasing dietary lipid levels. However, alanine aminotransferase (ALT) activity increased with dietary protein content. On the other side, pyruvate kinase (PK) activity increased with both dietary protein and lipid content. This study indicates that high dietary lipid (12%) improved the feed efficiency but did not reduce dietary protein demand in juveniles O. chrysurus.

Rearing performance of juvenile yellowtail snapper, Ocyurus chrysurus, in a sea water recirculation system at two different stocking densities

“…The FCR of both treatments coincides with that described by Arenas et al (2021) for the evaluation of different diets for juvenile stages (13.7 ± 0.45 g) in yellowtail snapper. For the same species reared in cages, an FCR of 1.35 was obtained without considering the humidity of the feed; otherwise, it would be 4.54 (García Torcuato et al, 2006).…”

“…Another reason is the relation between the amount of protein and lipids in the food and protein the organism can assimilate. Arenas et al (2021) obtained the best growth results with high protein and lipid levels (50% and 12% respectively) in juvenile stages. Although the diet of yellowtail snapper is based on penaeid crustaceans (Rinc on-Sandoval et al, 2009), is possible that the amount of protein in the diet was higher than the requirements of the organisms at this size.…”

“…It is important to mention that the food used was not created specifically for this species; this reason could also be why the FCR was higher than in species. A correct balance of protein and carbohydrates could improve the feed efficiency (Arenas et al, 2021).…”

Evaluation of in vitro and in vivo digestibility of potential feed ingredients for juvenile Yellowtail Snapper

“…Enríquez et al (2017) reported better growth performance in juvenile Yellowtail Snapper that received protein at a rate of 50 g/kg of diet. Furthermore, Arenas et al (2021aArenas et al ( , 2021b investigated the effect of increasing dietary lipid content on the growth of Yellowtail Snapper. They found that the feed efficiency of this species improved when the lipid content increased from 60 to 120 g/kg.…”

“…They found that the feed efficiency of this species improved when the lipid content increased from 60 to 120 g/kg. In addition, Arenas et al (2021aArenas et al ( , 2021b reported that Yellowtail Snapper had a low ability to use digestible carbohydrates as energy substrates. It is important to note that specific growth rates for Yellowtail Snapper were reported in these studies; Arenas et al (2021aArenas et al ( , 2021b reported a specific growth rate of 1.26% per day, while Enríquez et al (2017) reported a specific growth rate of 1.01% per day.…”