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Growth rate, feed efficiency, and mortality were not adversely affected by reducing the level of herring meal in an open formula dry-pellet diet fed to rainbow trout (Salmo gairdneri) in aquaria through which 80–90% of the effluent water was recirculated. The herring meal was reduced from 35 to 18%, and the level of soybean meal increased from 10 to 39%. The fish gained 5.5 and 5.4 kg/100 fish from 8 to 40 wk of age on the high and low herring meal diets, respectively. Deletion of brewers' yeast, corn fermentation extractives, and whey powder from the diet with the higher level of herring meal increased weight gain to 7.0 kg/100 fish. When the fermentation by-products were removed from the diet with the lower level of fish meal the gain was reduced to 4.8 kg/100 fish. All the diets contained 4% of soybean or rapeseed oil or a marine oil; the type of oil did not influence the gains, but the conversion of feed to gain was most efficient for the diet containing the marine oil. The apparent digestibilities of the proximate components of three of the diets suggested that the fermentation by-products were not as digestible to the fish as the other components of the diet.

The formation of phosphatidylcholine by acylation of 1-acyl-sn-glycero-3-phosphorylcholine with fatty acids was demonstrated in microsomal preparations from the livers of rainbow trout (Salmo gairdneri). Maximum incorporation of fatty acids into phosphatidylcholine was highly dependent upon the addition of 1-acyl-sn-glycero-3-phosphorylcholine to the incubation medium when activated acids in the form of [14C]acyl-CoA esters were provided. The acyl-CoA: 1-acyl-sn-glycero-3-phosphorylcholine acyltransferase showed a selectivity for unsaturated (oleate) over saturated (palmitate) fatty acids when microsomes were prepared from rainbow trout acclimated to 7 or 15 C and assays conducted at both temperatures. The presence of an acyl-CoA hydrolase in the microsomal preparations is also reported. The possible function of the acyltransferase in rearranging the fatty acid composition of cellular phospholipid when fish are exposed to a change in environmental temperature is discussed.

Peroxide value (PV), anisidine value, and thiobarbituric acid (TBA) number were compared as methods for measuring oxidation in fish oils and fish diets. PV was the method of choice for estimating oxidation in the oil. Methods for measuring moderately oxidized oil after being mixed in the diets are discussed. Analyses of dietary samples revealed that the TBA numbers and percentages of polyunsaturated fatty acids were not greatly altered by the addition of moderately oxidized fish oil and by the long-term storage (24 wk) of the diet at room temperature. However, endogenous α-tocopherol levels in the diet were significantly (P

Subadult rainbow trout (Salmo gairdneri) were fed diets containing hexachlorobenzene (HCB) to establish mean body burdens of 225 and 440 μg HCB per fish. They were sampled after 0, 24, 55, and 110 d to estimate the rate of elimination. The biological half-life or T[Formula: see text] of HCB for trout under the prescribed laboratory conditions was estimated to be at least 7 mo, and perhaps as long as several years. T[Formula: see text] was calculated using body burden or μg HCB per fish, and tissue concentrations or μg/kg HCB. Estimates of T[Formula: see text] derived from tissue concentrations ranged from 61 to 117 d, but this was shown to be due to a relative increase in body weight over the study period. The implications of increasing body weight on kinetics measurements are discussed, and an equation is presented that adjusts for changes in body weight where estimates of T[Formula: see text] are calculated using tissue concentrations.The results of this and other studies on HCB were used to examine the kinetics of HCB in salmonids collected from Lake Ontario. Using the information derived from laboratory studies on rainbow trout, good agreement was achieved between the expected level and that monitored in field samples of rainbow trout, but only a fair agreement was suggested for lake trout (Salvelinus namaycush) and coho salmon (Oncorhynchus kisutch). Differences in the HCB kinetics of these species may be attributed to body weight, age, and perhaps feeding habits. Concentrations of HCB reported in field sampling programs generally range from 1 to 100 μg/kg in fish, and it is suggested that these levels are primarily due to the limited availability of HCB in the Lake Ontario environment.Key words: contaminants, hexachlorobenzene (HCB), half-life, elimination, depuration, rainbow trout, Salmo gairdneri; Lake Ontario

Rainbow trout (Salmo gairdneri) acclimated to 19 °C and fed a pelleted diet of either 6% soybean oil or 6% tallow fat had similar plasma thyroxine levels (0.62 ± 0.10 and 0.69 ± 0.08 μg/100 ml, respectively), although fish acclimated to 7 °C and fed the soybean diet gave significantly (P

Semi-purified diets containing either soybean or rapeseed meal were fed to four barrow pigs of 60-kg liveweight in balance study cages. Comparison of feed intake and feces and urine output showed that the apparent digestibilities and biological values of the soybean meal-containing diet were 87.8 and 84.0%, respectively; the corresponding values for the rapeseed meal-containing diet were 78.4 and 78.9%. Samples of feed and feces were hydrolyzed and the n-propyl N-acetyl esters of the amino acids were prepared and separated by gas-liquid chromatography. Apparent digestibilities of the amino acids in the two protein sources were calculated; for soybean meal the values ranged between 85 and 92%, with the exception of methionine, for which the value was only 79%; the value for lysine was 90%. The corresponding values for rapeseed meal were 74 and 86%, with values of 87% for both methionine and lysine. An attempt to use polyethylene glycol as a digestion indicator failed, because rapeseed meal appeared to contain material which interfered with the development of turbidity; however, for the soybean meal-containing diet there were no significant differences between the apparent digestibility values determined with the indicator and those determined using total feces collection.

A 15% protein corn-soy finisher diet was compared with an isonitrogenous corn-soy-rapeseed meal diet. The two diets were fed either as meal or as pellets. Twenty female pigs received each of the four experimental treatments from 45 to 90 kg liveweight. The treatments did not affect feed consumption and the substitution of 11% rapeseed meal in the diet fed as meal did not affect growth rate. Pelleting increased the growth rate of pigs on the corn-soy diet, but had no effect on the growth rate of the pigs receiving the corn-soy-rapeseed diet.The digestible energy value of the rapeseed meal and of the reground, pelleted rapeseed meal was determined using barrows of 50 kg liveweight. The digestible energy value of the rapeseed meal (2.74 kcal/g) was increased to 3.02 kcal/g by steam pelleting and regrinding.