Effect of dietary fish meal and fish oil replacement on lipogenic and lipoprotein lipase activities and plasma insulin in gilthead sea bream (Sparus aurata)

The effects of a double replacement of fish oil (FO) and fish meal (FM) by dietary vegetable ingredients in juvenile gilthead sea bream (Sparus aurata L. 1758) on some indices of lipid metabolism and plasma insulin levels were analysed. Four experimental diets with a replacement of 75% of FM by plant proteins (PP) were administered. Added oil was either FO (75PP/FO diet), or a vegetable oil mix (VO), replacing 33%, 66% or 100% of FO (75PP/33VO, 75PP/66VO, 75PP/100VO diets). Another diet with 50% of substitution of FM by PP and with 100% of VO was also tested (50PP/100VO diet). Final body weight was similar in all diet groups, except for the 75PP/100VO group, which presented lower values. Circulating insulin levels increased with feed administration in all groups and no differences between diets were observed, with the exception of the 75PP/FO group, which presented higher plasma insulin values. In adipose tissue, glucose‐6‐phosphate dehydrogenase and malic enzyme activities decreased with the inclusion of vegetable oil, especially 5 h after feeding. Diet had no significant effect on the hepatic activity of either enzyme. Lipoprotein lipase activity decreased in white muscle and adipose tissue with the replacement of fish oil in 75PP diets, 5 h after feeding. In conclusion, the use of a combined replacement of fish oil and fish meal by vegetable ingredients in gilthead sea bream permits satisfactory growth, with moderate changes in tissue lipogenesis and lipid uptake.     

Effect of supplemental dietary zinc sources on the growth and carbohydrate utilization of tilapia Smith 1840, Oreochromis niloticus × Oreochromis aureus

An 8‐week feeding trial was conducted to investigate the effect of supplemental dietary zinc sources on the growth performance and carbohydrate utilization of juvenile tilapia Smith 1840, Oreochromis niloticus × O. aureus. The goal was to compare the bioavailability of two zinc sources, zinc sulphate (ZnSO₄) or zinc methionine (ZnMet), by using two practical basal diets with 350 g kg^?1 (C350) or 400 g kg^?1 (C400) carbohydrates based on wheat as the carbohydrate source. The results showed that fish fed with a diet supplemented with 60 mg kg^?1 Zn from either ZnSO₄ or ZnMet had a significantly (P < 0.05) greater specific growth rate and protein efficiency ratio than those fed with the diets of ≤30 mg kg^?1 Zn. The composition of tilapia carcass was also found to be influenced by various levels of dietary zinc from the two zinc sources. The G6P‐DH in fish fed with the 20 mg kg^?1 ZnMet diet and the PK levels in fish fed with 20 mg kg^?1 ZnSO₄ and 30 mg kg^?1 ZnMet diet were significantly (P < 0.05) higher than those in fish fed with the C400 diet. The data suggest that supplemental dietary zinc from either ZnMet or ZnSO₄ significantly affects the growth performance and carbohydrate utilization of tilapia.     

Do plant‐based diets for Atlantic cod (Gadus morhua L.) need additions of crystalline lysine or methionine?

Atlantic cod (Gadus morhua), initial weight 15 g, were fed ten experimental diets for 15 weeks. The diets were based on a mixture of plant proteins (PP) and fish meal (FM), where PP constituted 65% of dietary protein. PP mixtures were chosen to reach as low levels of lysine and methionine as possible. The diets were supplemented with increasing amounts of lysine (19.2–31.9 g kg^?1 diet) or methionine (9.4–12.3 g kg^?1 diet), in a regression design. No growth difference among diet groups was found in the plant‐based diets. Increased dietary lysine resulted in decreased liver size, plasma triacylglycerol concentration (TAG) and lipid productive value (LPV). Methionine additions did not result in changed Hepatosomatic index (HSI), LPV or plasma TAG. Feed conversion ratio (FCR) and protein utilization were neither affected by lysine nor methionine. Plasma and muscle concentrations of free lysine and methionine correlated with dietary levels 5‐h post feeding. Overall conclusion was that cod maintain growth rates in plant‐based diets if dietary protein was high, without additional supplements of crystalline lysine or methionine. Lysine intake significantly influenced lipid metabolism, showing the necessity to add lysine in plant protein‐based diets to hinder increased lipid deposition. No such effects were found because of lack of methionine additions.     

Relationship between nutritional and rearing parameters of Octopus maya juveniles fed with different rations of crab paste

To study the effect of feed ration on rearing and nutritional conditions of Octopus maya juveniles (7–10 days old), two groups of octopuses were fed on 10% and 30% rations, using a crab paste agglutinated with gelatine, when compared to another control group fed ad libitum on crab muscle tissue. The agglutinated diet was well accepted by the octopuses at this early stage. When considered together, the marginally higher survival of the 30% group and probably higher levels of the other rearing performance parameters (growth and feeding rate) indicate that this feed ration is more adequate than a 10% feed ration for rearing O. maya under these conditions. Octopuses fed 30% also generally showed higher total energy per gram of arm tissue and oxygen consumption, as well as different proteolytic activity. In addition, the mentioned nutritional differences influenced by the feed ration were found to be statistically correlated to the promoted growth and the end survival and feeding rates.     

Effect of masking organoleptic properties of fat on diet self‐selection by the sparid Diplodus puntazzo

Fish are able to select a balanced diet according to their nutritional needs by choosing among incomplete feeds or even pure macronutrients. However, the relevance of both the organoleptic properties of diet and the postingestive signals that they produce remains unclear. Thus, sharpsnout seabream were allowed to select between diets containing different edible oils with their organoleptic properties masked by using gelatine capsules. Fish were fed capsules of two different colours so that they could associate the capsule colour with its corresponding postingestive effect. The longitudinal experiment included a first phase during which the fish were adapted to consuming the gelatine capsules. In a second phase, the fish were challenged with two different encapsulated diets: one comprising a complete diet containing fish oil and the other a fat‐free diet. Sharpsnout seabream showed a preference for the fish oil capsules (3.8 ± 1.1 g kg^?1 body weight (BW), 66.8% of total intake) over the fat‐free capsules, showing that they were able to associate the colour of the capsule with their nutritional content through postingestive signals. After that, the fish were challenged to select between the capsules containing the fish oil diet and capsules containing a vegetable oil (linseed or soybean), in which case they showed no preference between diets (2.4 ± 0.3: 2.1 ± 0.5 g kg^?1 BW of fish oil versus linseed oil capsules and 2.2 ± 0.2: 1.8 ± 0.6 g kg^?1 BW of fish oil versus soybean oil capsules), indicating that the fatty acid composition of the different oils was not sufficient to affect dietary selection through postingestive signals. So, in conclusion, when orosensorial information from food is absent, the fish are able to select between diets at a macronutrient level by using postingestive information. However, this information is not sufficient for distinguishing between diets that differ in the type of oil used.     

Effect of dietary inclusion of various plant ingredients as an alternative for Sargassum thunbergii on growth and body composition of juvenile sea cucumber Apostichopus japonicus

Two feeding experiments were conducted to investigate the effects of dietary inclusion of different plant ingredients on growth and body composition of juvenile sea cucumber. In the first experiment, three replicate groups of the sea cucumber (average weight of 1.5 ± 0.05 g) were fed one of the seven experimental diets containing Sargassum thunbergii (CON), Undaria (UND), Laminaria (LAM), Brassica oleracea L. var. capitata (BRA), fermented soybean (FSB), distillers dried grain (DDG) and rice straw powder (RIC) for 10 weeks. After the feeding trial, survival was not significantly different among the dietary treatments. Specific growth rate (SGR) of sea cucumber fed the FSB diet (0.73) was significantly higher than that of sea cucumber fed the other diets (P < 0.05), except for the DDG diet (0.64). The lowest SGR was observed in sea cucumber fed the CON diet (0.14). Based on the result of the first experiment, the second experiment was conducted to determine the proper level of dietary DDG for growth of juvenile sea cucumber. Three replicate groups of sea cucumber (average weight of 1.6 ± 0.02 g) were fed one of the five experimental diets containing different levels (g kg^?1) of DDG (DDG0, DDG10, DDG20, DDG30 and DDG40) for 12 weeks. Survival was not significantly different among the treatments (P > 0.05). The best SGR was obtained in sea cucumber fed the DDG10 diet (10.1) and the value of sea cucumber fed the DDG40 diet (5.6) was the lowest (P < 0.05). The SGR of sea cucumber fed the DDG10 diet did not differ from that of sea cucumber fed the DDG20 diet (P > 0.05). Moisture, crude protein, crude lipid and ash contents of whole body in sea cucumber among the dietary treatments (P > 0.05) did not differ significantly at both experiments. Results of two feeding trial suggest that dietary inclusion with 100 g kg^?1 FSB or 100–200 g kg^?1 DDG may improve growth of juvenile sea cucumber, and especially DDG could be used as a good ingredient for the low‐cost feed formulation.     

Effect of dietary thiamin supplement on immune responses and intestinal microflora in juvenile Jian carp (Cyprinus carpio var. Jian)

This study was to investigate the effect of dietary thiamin on the immune response and intestinal microflora in juvenile Jian carp (Cyprinus carpio var. Jian). Seven diets (0.25, 0.48, 0.79, 1.06, 1.37, 1.63 and 2.65 mg thiamin kg^?1) were fed to Jian carp (8.20 ± 0.02 g). At the end of feeding trial, red blood cell counts and white blood cell counts increased with increasing dietary thiamin levels up to 0.79 and 1.06 mg kg^?1 diet, respectively (P < 0.05); Lactobacillus counts in intestine increased gradually, and maximum values obtained when the thiamin level was at 0.79 mg kg^?1 diet (P < 0.05). After the feeding trial, fish were injected with Aeromonas hydrophila only one time on the first day of the challenge trial and fed the same diets as the growth trial for 17 days. The survival rate, leucocyte phagocytic activity, lectin potency, acid phosphatase activity, lysozyme activity, total iron‐binding capacity and immunoglobulin M content of fish after being injected with A. hydrophila were all improved with increasing dietary thiamin levels up to a point, respectively (P < 0.05). These results suggested that thiamin could improve immune response and the balance of intestinal microflora of juvenile Jian carp.     

Growth performance of the white shrimp,Litopenaeus vannamei,fed on practical diets with increasing levels of the Antarctic krill meal,Euphausia superba,reared in clear‐ versus green‐water culture tanks

Litopenaeus vannamei were stocked in 25 clear‐water 500‐L tanks at 100 shrimp m^?2 and in 25 green‐water 1000‐L tanks at 60 animals m^?2. Four diets were formulated to include krill meal at 10, 50 or 110 g kg^?1; or krill oil at 25 g kg^?1 by replacing fish meal, fish oil, soybean lecithin and cholesterol. Diets had similar levels of crude protein, total energy and essential amino acids. After 72 days, shrimp reared in clear and green water showed no differences in performance among diets. In clear water, shrimp attained 13.1 ± 0.59 g body weight, 1.00 ± 0.06 g week^?1 growth, 81.4 ± 7.3% survival, 780 ± 118 g m^?2 yield, 16.9 ± 1.8 g shrimp^?1 apparent feed intake (AFI), and 2.18 ± 0.29 food conversion ratio (FCR). In green water, shrimp attained 14.3 ± 0.81 g body weight, 1.04 ± 0.09 g week^?1 growth, 91.4 ± 5.4% survival, 569 ± 69 g m^?2 yield, 20.9 ± 3.2 g shrimp^?1 AFI, and 2.22 ± 0.34 FCR. Diets containing krill meal or krill oil were able to fully replace the protein and lipid value of fish meal, fish oil, soybean lecithin and cholesterol at no cost to performance.     

Effects of dietary methionine hydroxy analogue supplement on growth,protein deposition and intestinal enzymes activities of juvenile Jian carp (Cyprinus carpio var. Jian)

A total of 900 juvenile Jian carp (Cyprinus carpio var. Jian) (8.24 ± 0.03 g) were fed practical diets containing graded levels of methionine hydroxy analogue (MHA) (0, 5.1, 7.6, 10.2, 12.7 and 15.3 g kg^?1 diet) for 60 days to investigate the effects of MHA on growth, protein deposition and intestinal enzymes activities. Per cent weight gain (PWG) significantly increased with increasing levels of MHA up to a point (P < 0.05), and thereafter declined. Feed efficiency was the highest when MHA level was at 5.1 g kg^?1 diet. Feed intake (FI) significantly enhanced with dietary MHA level up to a point (P < 0.05), beyond which it plateaued. Patterns of differences in protein production value, lipid production value, intestosomatic index, folds height, lipase, chymotrypsin, γ‐glutamyl transpeptidase, Na⁺, K⁺‐ATPase, creatinekinase, glutamate‐oxaloacetate transaminase and glutamate‐pyruvate transaminase activities were the same as that in PWG, whereas the trend of plasma ammonia content was opposite. Hepatopancreas protein content, trypsin and amylase activities followed the same trend as that of FI. The optimal supplemental level of MHA for fish meal and miscellaneous meals–based diet (6.9 g methionine kg^?1 diet) for PWG was 8.2 g kg^?1 diet by the quadratic regression analysis.