Geology topics

R. E. Austic

Publications and source records attributed to R. E. Austic.

4 recordsLinked to original sources

USGS1988

Effect of feeding level and dietary electrolytes on the arginine requirement of rainbow trout (Salmo gairdneri)

Experiments were conducted to determine the effect of level of feeding (restricted feeding and feeding to satiation) and dietary variations in the balance of monovalent minerals on the arginine requirement of rainbow trout fingerlings. Based on growth and efficiency of feed utilization for growth, the arginine requirement was lower (3.5% of protein) when fish were fed to satiation than when they were fed at a restricted level (4.2% of protein). When calculated on the basis of the amount of arginine consumed per day, however, the requirements were similar for fish subjected to the two methods of feeding. Three balances (acidic, neutral, and alkaline) of sodium, potassium and chloride were used in several experiments. The arginine requirement tended to be higher when fish were fed diets containing the alkaline as compared to the acidic balance of minerals. These studies indicate that the method of feeding has a significant effect on the dietary concentration of arginine needed to maximize growth rate and feed utilization in rainbow trout.

Aquaculture↗

USGS1987

Interactions among dietary minerals, arginine and lysine in rainbow trout (Salmo gairdneri)

Studies were conducted to determine whether interactions occur among dietary lysine, arginine and monovalent minerals in rainbow trout. In one experiment, rainbow trout fingerlings were fed diets containing three levels of lysine (2.4, 3.1 and 3.8 g per 100 g diet), two levels of arginine (1.7 and 2.5 g per 100 g diet) and two mixtures of Na + K + and Cl in a 3×2×2 factorial design. The mixtures varied in the proportions of cations to anions such that Cl equalled the sum of Na + and K + (cations − anions = 0 mEq/kg diet) in one mixture and exceeded the sum of Na + and K + (cations − anions = −200 mEq/kg diet) in the second mixture. Growth and efficiency of feed conversion were not affected by dietary lysine and arginine in fish fed diets containing − 200 mEq/kg balance, but when fish were fed diets containing a 0 mEq/kg balance, 3.8% lysine and a combination of 3.1% lysine and 2.5% arginine depressed both measures of response. Trout receiving the 0 mEq/kg cation-anion balance had significantly higher free histidine concentrations and lower free lysine concentrations in muscle and higher hepatic arginase activity (P≤0.01) than those receiving −200 mEq/kg. In another experiment, trout were fed diets containing three levels of K + (21, 191 and 360 mEq/kg), two levels of Na + (21 and 191 mEq/kg) and two levels of Cl − (179 and 347 mEq/kg) in a 3×2×2 factorial design. Growth and efficiency of feed conversion were depressed and hepatosomatic index increased with higher levels of dietary K + (P≤0.01), Na + (P≤0.05) and Cl (P≤0.01), with significant K + x Cl + (P≤0.01) and K + x Na + x Cl (P≤0.05) interactions. Increasing dietary K + resulted in increased levels of muscle free histidine and decreased levels of muscle free lysine and arginine (P≤0.01), while increasing dietary Cl increased muscle free lysine, the effect of which was dependent on dietary potassium (K + x Cl − , P≤0.01). It is concluded that dietary levels of K + , Na + and Cl − , irrespective of overall cation-anion balance of these minerals, affects growth rate, efficiency of feed utilization and the metabolism of basic amino acids in tissues of trout. Excess lysine causes depressed growth and efficiency of feed utilization. These effects were due to a lysine toxicity rather than a lysine-arginine antagonism, as they were not prevented by supplemental dietary arginine.

Fish Physiology and Biochemistry↗

USGS1986

Urea cycle activity and arginine formation in rainbow trout (Salmo gairdneri)

Studies were conducted to determine whether rainbow trout fingerlings possess the ability to synthesize arginine via the urea cycle. Several urea cycle enzymes were detected in trout tissues. An experiment was conducted to determine whether the enzymes increase in response to starvation or in response to dietary protein level (0, 30, 40, 50% protein). Although some effects were observed, they did not appear to be consistent with the function of the urea cycle as a mechanism of detoxifying ammonia in the fish. The activities of kidney arginase and liver and muscle carbamoyl phosphate synthetase (CPS) were higher ( P < 0.05) when protein was omitted from the diet ( P < 0.05) than when it was present but were unaffected by protein level otherwise. The activities of liver arginase and kidney and muscle CPS and ornithine transcarbamoylase (OTC) were higher ( P < 0.05) in starved fish than in fish that received adequate levels of protein. Liver CPS and OTC were lower in starved fish than in fish fed 30% protein. L-[l- 14 C]ornithine hydrochloride and L-[ carbamoyl - 14 C]citrulline, injected intraperitoneally, were incorporated into tissue arginine, a finding consistent with arginine biosynthesis via the urea cycle. When one-half of dietary arginine was replaced by equimolar amounts of glutamic acid, ornithine or citrulline, glutamic acid markedly reduced growth ( P < 0.05), whereas growth was depressed only slightly by ornithine ( P < 0.05) and not depressed by citrulline ( P > 0.05). We conclude that trout have a urea cyle that provides for potential arginine biosynthesis.

Journal of Nutrition↗

USGS1984

Effect of dietary electrolytes and histidine on histidine metabolism and acid-base balance in rainbow trout ( Salmo gairdneri )

1. Rainbow trout fingerlings were fed diets containing 1.2, 1.8 and 2.6% histidine and two mixtures of Na, K and Cl ( Na + K - C l = 0 or -200 meq / kg diet ) in a factorial design. 2. Growth and efficiency of feed conversion were not affected by histidine in the diet when it contained the −200 meq/kg electrolyte mixture, but with the 0 meq/kg level, 2.6% histidine depressed both measures of response. 3. Histidine increased plasma and muscle histidine levels, increased hepatic histidase activity, but did not affect hepatic histidine-pyruvate aminotransferase activity. 4. Muscle-free histidine concentrations were markedly higher and lysine concentrations were lower in trout receiving 0 meq/kg than those receiving the −200 meq/kg electrolyte mixture. 5. The electrolyte balance of the diet has a marked effect on the metabolism of histidine in trout.

Comparative Biochemistry and Physiology, Part B: C↗