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A feeding experiment was conducted to evaluate the supplemental effect of bile salts to a defatted soybean meal-based non-fish meal diet for rainbow trout Oncorhynchus mykiss. A fish meal-based diet (FM) and two non-fish meal diets with and without bovine bile salts (SC + B and SC, respectively) were fed to fish (13 g initial weight) for 10 weeks. Fish fed diet SC showed inferior growth and feed efficiency, while bile salt supplementation improved the parameters to the same levels as fish fed diet FM. Crude fat and starch digestibility of diet SC-fed fish decreased after the 10-week feeding trial compared to the data obtained with fish that had no experience of the diet. Total biliary bile salt content and intestinal maltase activity of fish fed diet SC were the lowest among treatments, while these parameters were improved by bile salt supplementation. Morphological changes occurred in the distal intestine and liver of the diet SC group, although the histological features of fish fed diet SC + B were similar to those of fish fed diet FM. These results suggest that bile salt supplementation to a soybean meal-based diet improves the nutrient utilization by normalizing digestive processes in rainbow trout.

An experiment was conducted to investigate the effect of various organic acid (OA) supplementation on phosphorus (P) and nitrogen (N) retention by rainbow trout fed low fishmealbased diets. Six experimental diets were formulated, and diet 0.5P was arranged as a positive control diet with 0.5% calcium phosphate and OP as a negative control without additional P. Diets CA and LA were supplemented with 1% citric (CA), and lactic (LA) acids, respectively, and diets MHA and LTE were supplemented with 1% methionine hydroxy analog (MHA) and 1% liquid trace elements (LTE), respectively. Fish fed CA and LTE showed similar growth to that of the positive control diet. P retention was lowest in the 0.5P group and was elevated with CA and LTE diets. Therefore, in this study it is suggested that it might not be necessary to supplement the low fishmeal-based diet of rainbow trout with P if certain organic acids such as CA are added.

:  The physiology of yellowtail fed a non‐fishmeal diet was examined, with a specific interest in the role of taurine in disease resistance and cholesterol metabolism. Decrease of disease resistance in fish fed a non‐fishmeal diet was confirmed by mortality due to natural infection with pseudotuberculosis and artificial infection with Lactococcus garvieae. It is suggested that the most important symptoms related to decrease of disease resistance in fish fed a non‐fishmeal diet is anemia. Anemia was improved by supplementation with taurine. Significant elevation of relative expression of HMG‐CoA reductase mRNA in fish fed a non‐fishmeal diet suggests that cholesterol synthesis would be activated and not dysfunctional. Plasma cholesterol of these fish was elevated to the levels of control fish by supplementation of both cholesterol and taurine. These results suggest that hypocholesterolemia observed in fish fed a non‐fishmeal diet compared with a fishmeal diet would be caused by insufficient dietary cholesterol and decrease of endogenous cholesterol due to the lack of dietary taurine.

To investigate the cause of morphological changes occurring in the liver and intestine of rainbow trout Oncorhynchus mykiss fed defatted soybean meal (SBM)-based non-fish meal diets, morphological observations were conducted on fish fed casein-based semipurified diets supplemented with soybean antinutritional factors (soya saponin, soya isoflavone, soya lectin, oligosaccharide, Ca-phytate and their mixture). Hepatocytes and the epithelial cells in the hepatic ducts were not atrophied in any of the treatments. Lack of microvilli and pinocytotic vacuoles, and fatty degeneration of the epithelial cells were observed in the distal intestine of fish fed diets containing soya saponin. The proliferation of connective tissue in the mucosal folds and submucosa was shown in the distal intestine of fish fed the diet containing all substances including lectin. These results suggest that both saponin and lectin are the responsible factors in SBM for the occurrence of morphological changes of the distal intestine in rainbow trout fed SBM-based diets.

This study was conducted to investigate the effect of dietary supplementation of cottonseed and soybean meal (CS) on growth performance, feed utilization, and gossypol accumulation in juvenile (mean body weight 11 g) Japanese flounder Paralichthys olivaceus. Five isonitrogenous and isocaloric experimental diets (designated CS0, CS10, CS20, CS30, and CS40) containing 0, 10, 20, 30, and 40% CS mixture (1:1 w/w) were formulated. After 9 weeks of feeding trial, fish fed all diets did not show significant differences in growth performances, feed utilization, and whole body compositions. Hemoglobin content gradually decreased (P < 0.05) with increments of CS inclusion levels. There was a positive linear relationship between dietary gossypol and total liver gossypol contents. Free radical scavenging activity in the experimental diets gradually increased with increment of dietary CS inclusion. This finding indicates that the mixture of cottonseed and soybean meal with methionine and lysine supplementation could replace up to 40% of fishmeal protein in diets. However, 20% fishmeal protein replacement by dietary inclusion of cottonseed (9.4%) and soybean (8.7%) meal might be the optimum and safe level for the commercial use of CS in juvenile Japanese flounder.

Twenty Lithuanian Black-and-White calves (10 bulls, 10 heifers) were used to evaluate the effects of the supplemental probiotic product, Enterococcus faecium M74 (2.4 g/day/calve), added to fresh milk and skimmed milk in a 56 day-study. The probiotic was administered by dietary supplementation to first group of calves and their respective pens (probiotic group), whereas the second group (control group) received no probiotic supplementation. The results of this trial indicate positive effects of the probiotic product Enterococcus faecium M74. The actual percentage of calves with diarrhoea was reduced from 50% to 20% among the calves fed the pre- and probiotic diet. Probiotic supplementation reduced the faecal count of clostridia and enterococci. The calves fed Enterococcus faecium M74 weighed more at 20, 40 and 62 days of age by 4.9%, by 9.7% (P less than 0.05) and by 9.4% (P less than 0.01), respectively, than the control calves. The calves fed Enterococcus faecium M74 had increased daily weight gains compared with the calves not fed a probiotic product. The average weight gain and the daily weight gain of the probiotic-supplemented calves were by 7.8 kg (P less than 0.01) and by 0.14 kg higher (P less than 0.01), resp., compared with the control calves. The calves given the Enterococcus faecium M74 also had forage and total DM intakes that were numerically higher than those fed the control diet, without any additive. During the 56 days experimental period, the average feed conversion rate was improved by 12.9% in the probiotic-treated group.

The effects of dietary taurine levels and lipid contents on the conjugated bile acid composition and growth performance of juvenile Japanese flounder Paralichthys olivaceus were investigated. Six types of diet (three different levels of taurine at two different levels of lipid) were fed to juveniles (average body weight, 0.04g). Fishmeal that was washed with 70% ethanol to remove taurine was used as the sole protein source. Feeding experiments were carried out at 20°C for 6 weeks. At the end of the experiments, fish were weighed and analyzed for free amino acids in the body and the composition of the conjugated bile acids. The body weight and percent weight gain of the juveniles were improved by the dietary taurine supplementation. The taurine contents of the whole body and tissues increased with the increase of the dietary taurine contents. The conjugated bile acids in the gall bladder consisted of taurocholic acid and taurochenodeoxycholic acid, which increased with the increase of the dietary taurine level. Taurocholic acid accounted for more than 95% of the total conjugated bile acids. This indicates that taurine is the sole amino acid to conjugate bile acid in Japanese flounder.

Dietary fish oil (FO) was replaced by olive oil (OO) in young yellowtail Seriola quinqueradiata to investigate its effects on growth, muscular fatty acid composition and prevention of color deterioration of dark muscle during storage. Yellowtail were fed one of four diets, where FO (80 g/kg diet) was replaced by OO (0, 25, 50 and 100%) for 40 days. No significant difference in growth was seen among the diet groups. In addition, these experimental diets did not affect the proximate compositions of the dorsal muscle, ventral muscle and the liver in these fish. Serum total protein, glucose and total cholesterol levels did not show significant differences; however, serum triglyceride levels were significantly higher in fish fed 50 and 100% OO diets. Fatty acid composition of ventral muscle reflected the composition of the respective diets. Dark muscle discoloration was reduced in fish fed OO diets after 12 to 18 h during storage at 4°C. Furthermore, the redness value of fresh dark muscle increased depending on the extent of FO replacement. These results indicate that the partial or total dietary replacement of FO with OO prevents discoloration of dark muscle without affecting the growth of young yellowtail after 40 days of feeding.

Inclusion of the water-soluble fraction of blue mussels Mytilus galloprovincialis as a feed additive was examined with tiger puffer Takifugu rubripes. The control diet mainly consisted of fish meal, potato starch, and pollack liver oil. Experimental diets were formulated to replace 30% and 40% of the fish meal protein with defatted soybean meal (SBM), and were supplemented with 0-20% mussel extracts. Fish of 18 g initial body weight were fed each diet to satiation, twice daily, 6 days per week for 7 weeks at 20degC. Weight gain and protein efficiency ratio of fish fed the diet containing SBM without the extract were significantly lower than those of the control at the 30% replacement level. Addition of 5% or 10% extract improved the growth and feed utilization to levels comparable to those of the control. At 40% substitution, statistically identical growth and feed performance to the control were obtained for diets supplemented with 10% or 20% extract; however, performance for 5% addition was significantly lower. Thus, the water-soluble fraction of blue mussels would be an effective feeding stimulant in aquaculture feed for tiger puffer that makes it possible to replace 30-40% of fish meal protein with SBM.