Determination of methionine requirement of juvenile silver catfish (Rhamdia quelen) and its effects on growth performance, plasma and hepatic metabolites at a constant cystine level

Abstract

This study was performed to determine the dietary methionine requirements and its effects on growth performance, plasma and hepatic metabolites for juvenile silver catfish. The fish (initial weight = 3.26 AE 0.3 g) were distributed in 24 experimental units (35 fish each). Six diets were formulated with increasing levels of methionine (09, 16, 23, 30, 37 and 44 g/kg protein diet). Each diet was distributed randomly to the groups, with four replicates fed twice daily to apparent satiation for 15 weeks.Methionine levels influenced in body composition (moisture and ash), and submit effect on liver metabolism and plasma. The relative weight gain (RWG) and specific growth rate (SGR) increased with highest levels of methionine to 30 g/kg protein in the diet, thereafter maintaining a nearly constant level of 1.9 g/kg cystine in the protein diet. The protein retention coefficient (PRC) also increased with increasing levels of up to 23 g/kg protein diet, thereafter maintaining a constant level of 1.9 g/kg cystine protein diet until beginning to decrease at a level of 44 g/kg protein diet. In conclusion, methionine is an essential amino acid for the growth of juvenile silver catfish and exhibits an efficient capacity when provided as a synthetic amino acid. Based on the RWG and SGR data, the methionine requirement of juvenile silver catfish was estimated at 34.42 and 35.85 g/kg of the CP or 12.74 g/kg and 13.26 g/kg of the diet respectively. K E Y W O R D S amino acid, protein retention coefficient, relative weight gain, sulphur

Effects of reduced protein level and dietary amino acid supplementation on growth, body composition and intestinal morphometry of silver catfish ( Rhamdia quelen )

“…In meager ( A. regius ) and yellow catfish ( P. fulvidraco ), the body mineral content was not influenced by diets supplemented with Lys and Met (Güroy et al., 2017; Jiang et al., 2018). However, some studies describe that the mineral content is associated with the growth of fish (Rotili et al., 2018). Our results suggest a relationship between the content of body mineral matter and the growth of fish fed diets supplemented with AA.…”

“…Closed snout ( Megalobrama amblycephala Yih) fed with Met had lower body protein content, and no increase in protein synthesis was observed with higher levels of this AA (Liang et al., 2016). In silver catfish ( R. quelen ) fed diets containing Met levels, there was no difference in body protein content (Rotili et al., 2018). The differences between the results can be attributed to dietary treatments and the characteristics of the species such as age and eating habits (Gao et al., 2019; Liang et al., 2016; Rotili et al., 2018).…”

“…In silver catfish ( R. quelen ) fed diets containing Met levels, there was no difference in body protein content (Rotili et al., 2018). The differences between the results can be attributed to dietary treatments and the characteristics of the species such as age and eating habits (Gao et al., 2019; Liang et al., 2016; Rotili et al., 2018). The inadequate balance of AA in the diet can result in increased body fat instead of protein synthesis (Espe, Rathore, Du, Liaset, & El‐Mowafi, 2010; Li & Robinson, 1998).…”

“…The positive and negative control diets were formulated without AA supplementation. Diets with 34% of CP were supplemented with 0.5% Lys (34L), 1.5% Met (34M) and both AA (34LM), above the AA requirements of species (Montes‐Girao & Fracalossi, 2006; Rotili et al., 2018). The diets were prepared by mixing the ingredients with the oil using a horizontal mixer.…”

“…This fish, an omnivorous feeding habit, performed well and deposited body protein when fed with 38% of the crude protein (CP) and 3,600 kcal energy digestive (ED) kg ‐1 in the diet (Signor, Signor, Feiden, Reidel, & Hayashi, 2004). Lys requirements were estimated based on weight gain and apparent net protein utilization: 4.50% and 5.10% of the CP (Montes‐Girao & Fracalossi, 2006), and Met was based on weight gain and specific growth rate: 3.43% and 3.57% of the CP (Rotili et al., 2018).…”