Methionine Intake in Rainbow Trout (Oncorhynchus mykiss), Relationship to Cataract Formation and the Metabolism of Methionine

Abstract

Young rainbow trout were given diets containing graded levels of methionine for 16 wk. Analysis of the weight gain and food efficiency data showed the methionine requirement to be not more than 0.76% of the diet (1.9% of dietary protein). Activities of regulatory enzymes of the transulfuration pathway, methionine adenosyltransferase and cystathionine synthase in trout liver were not altered by changes in methionine intake. Concentrations of free serine in liver and plasma of the trout were high at low levels of methionine intake but fell as dietary methionine increased. This implied decreased flux through cystathionine synthase at low methionine intakes. Large increases in liver and plasma taurine occurred at high methionine intakes, implying enhanced transulfuration activity. Liver ornithine decarboxylase activity was reduced at the lowest level of dietary methionine used but the activity of S-adenosylmethionine decarboxylase was unchanged. Eye lenses of the trout given these diets were examined by a scanning lens monitor. Analysis of focal length variability with this equipment demonstrated that, if abnormality of the lens is to be avoided, a higher concentration of dietary methionine (0.96% or 0.6% methionine + 0.36% cystine) is needed than that required to maximize growth.

An initial investigation replacing fish meal with a commercial fermented soybean meal product in the diets of juvenile rainbow trout

“…In particular, soybean meal typically does not have enough methionine to meet the nutritional requirements of rainbow trout [8,57]. Although PSG has slightly more methionine than soybean meal [58], it is still relatively low in comparison to that required in the diets of rainbow trout [59]. Yamamoto et al [60] found that amino acid supplementation was required for their experimental diet containing soybean meal.…”

An epidemiological study of cataracts in seawater farmed Atlantic salmon Salmo salar

“…Dis Aquat Org 45: [229][230][231][232][233][234][235][236] 2001 (1) zinc deficiency (Ketola 1979, Barash et al 1982, Richardson et al 1985, (2) riboflavin deficiency (Poston et al 1977, Hughes et al 1981, Barash et al 1982, (3) tryptophan deficiency (Poston & Rumsey 1983), (4) thiamine deficiency (Hughes 1985) and (5) methionine deficiency (Poston et al 1977, Barash et al 1982, Walton et al 1982, Cowey et al 1992. Other factors associated with cataract formation are rapid fluctuations in water temperature (Loewenstein & Bettelheim 1979, Bruno & Raynard 1994, Bjerkås & Bjørnestad 1999, rapid growth (Kincaid & Elrod 1991, fluctuations in the water salinity (Hargis 1991), triploid genetic constitution (Wall & Richards 1992), genetic identity (strain) (Kincaid & Elrod 1991), UV radiation (Cullen et al 1993), cholinesterase inhibitors (Fraser et al 1989) and electrolytic imbalance (Iwata et al 1987).…”

Nutritional requirements of fish

“…These values are in line with other recent measurements (total S amino acid requirement of 9-6 g/kg diet or 24 g/kg dietary protein C O L I N B. COWEY A N D C . YOUNG CHO Cowey et al (1992), arginine requirement 14 g/kg diet or 42 g/kg dietary protein ). These requirement values, for all three amino acids are very much at the low end of previously reported requirements for rainbow trout.…”