No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Different preference is modulated by the feeding stimulants supplementation in different Chinese soft-shelled turtle ( Pelodiscus sinensis ) basic diets
Aquaculture Nutrition
Abstract
Five 2-week feeding trials were conducted to investigate five stimulants on P. sinensis. Two isonitrogenous and isoenergetic diets were formulated, one contained 600 g kg–1 fishmeal (FM diet) and the other contained 420 g kg–1 fishmeal and 225 g kg–1 animal protein blend (APB diet), and each tested one stimulant with four levels. The feeding stimulant candidates were betaine, 2-carboxy-ethyl dimethyl sulphonium bromide (DMPT), inosine-5′-monophosphate (IMP), taurine and squid extract. In the experiment on each stimulant, turtles (10.85 ± 0.10 g) were equally divided into FM and APB groups and fed with an equal mixture of corresponding diets containing four levels of stimulants, respectively. Each diet contained a unique rare earth oxide as inert marker. Turtles were fed twice daily (8:00 and 17:00), and faeces were collected. Preference for each diet was estimated based on the relative concentration of each marker in the faeces. In the FM group, only IMP showed the enhanced attraction. But in APB groups, all the stimulants, except IMP, showed higher preference than basal diets for at least one inclusion level, and the optimum level was 10 g kg–1 for betaine, 0.1 g kg–1 for DMPT, 0.1 g kg–1 for IMP, 5 g kg–1 for taurine and 10 g kg–1 for squid extract, and the squid extract had the strongest stimulating effect among the stimulants.
... RPS diet was different from the RP diet by the inclusion of 1% squid paste. This concentration of squid paste was determined by the optimal dietary preference of Pelodiscus sinensis (Sun et al., 2018a;Sun et al., 2018b). To maintain the consistencies of essential amino acid profiles in the experimental diets, microcapsule lysine was supplemented according to the essential amino acid profiles of the CT diet. ...
... Three experimental feeds were randomly assigned to turtles with quadruplicate tanks. Management of the feeding trial was conformed to the method of Sun et al. (2018a) and Sun et al. (2018b). Feed pellets were put on a sedentary plate under the water. ...
... In the present study, turtles fed diets included squid paste presented lower peak mRNA level of CCK and CCK1R than that in other groups. It might be accounted for the improved activities of the digestive enzyme in the RPS group (Sun et al., 2018a;Sun et al., 2018b). Similar results were also found in grass carp (Liu et al., 2014;Huang et al., 2019). ...
Background
As the primary source of protein for aquaculture, fishmeal has reached the extremity of sustainable development, our previous studies have proven that rice protein concentrate and squid paste are outstanding protein source and stimulant for Pelodiscus sinensis . However, little attention has been given to the molecular mechanism of the appetite modulated by the dietary nutrient factor, especially for a reptile. Thus, the present study aimed to evaluate feed intake and brain-gut dynamic responses to dietary rice protein concentrate and squid paste in Chinese soft-shelled turtle Pelodiscus sinensis .
Methods
Three isonitrogenous and isoenergetic practical diets were formulated including 60% fishmeal (CT), 42% fishmeal + 18% rice protein concentrate (RP) and 42% fishmeal + 18% rice protein concentrate + 1% squid paste (RPS), respectively. Microcapsule lysine was supplemented in RP and RPS diets to balance the amino acid profile. Turtles (initial weight 30.65 ± 0.97 g) were fed three times daily to apparent satiation. After the 8-week feeding trial, the turtles were exposed to 48h food deprivation, then the dynamic expression of the orexigenic and anorexigenic peptides were measured.
Results
The results showed that no significant effect was observed on feed intake when fishmeal was replaced by rice protein concentrate ( P = 0.421), while significantly improved feed intake was found by squid paste supplemented ( P = 0.02). The mRNA expression of anorexigenic peptides, such as leptin receptor, insulin receptor, pro-opiomelanocortin, cocaine and amphetamine-regulated transcript, cholecystokinin (and its receptor) and glucagon-like peptide-1 receptor in the brain increased significantly at 3 h past feeding ( P < 0.05), and then decreased. Nevertheless, neuropeptide Y and peptide YY mRNA expression showed the valley at 3h and peak at 12h past feeding. Intestinal cholecystokinin receptor and glucagon-like peptide-1 receptor mRNA expression showed no difference during the postprandial time ( P > 0.05). The results suggested that squid paste is an outstanding stimulant for Pelodiscus sinensis . Furthermore, the orexigenic and anorexigenic peptides evaluated here might play an essential role in short-term fasting to this species, of which the dynamic expression levels were regulated by squid paste.
... The recommended protein level for Chinese softshell turtle (Pelodiscus sinensis) is 39.0-47.7% DM (61,62,63,64,65,66,67,68). In red-eared terrapins (Trachemys scripta elegans) a growth rate equal to the natural one was obtained with 25-40% CP (50). ...
... The recommended EE level for Chinese softshell turtle in commercial farms is around 4.2-8.8% (74,64,65,66,67,68,70,71,72). High-fat diets (13.9% EE) should be avoided as they lead to the accumulation of lipids in the liver and liver injury (65). ...
Captive chelonians should be fed a natural diet to achieve a growth rate similar to that of free-ranging animals. A wide range of commercially formulated foods dedicated to chelonians is available. Feeding commercial foods has the advantage of convenience. On the other hand, species-specific information on the nutritional requirements of chelonians is not available yet. The aim of this study was to analyse and evaluate commercial pellets and feeds for chelonians. Commercial pellets (ntortoise = 7, nturtle = 7, from 6 companies) dedicated to carnivorous aquatic turtles and herbivorous terrestrial tortoises, and other aquatic turtle feeds (lyophilised beef heart, dried aquatic invertebrates, and whole frozen fish) were bought in pet shops. Whole frozen fish served as a reference feed for carnivorous aquatic turtles. The chemical composition as well as calcium (Ca) and phosphorus (P) contents were determined. Single-sample t-test was used with the label information as null hypothesis and the results of own parallel analyses for crude protein (CP), ether extract (EE), crude fibre (CF), Ca and P. The labelling of some of the pellets was deficient as nutritive values, Ca or P data were missing (tortoise pellets: 4 out of 7; turtle pellets: 5 out of 7). The label data differed significantly (p<0.05) from the results of our own analysis for 13 out of the 14 pellets. None of the tortoise pellets met the requirements of the animals completely. Because of the inadequate Ca:P ratio only one turtle pellet could be accepted. Accordingly, none of the commercial pellets can be recommended as main or only feed. Key words: nutrition; pellet; metabolic bone disease; chelonian VREDNOTENJE KOMERCIALNIH ŽELV IN KRME ZA ŽELVE Izvleček: Želve v ujetništvu je potrebno hraniti z naravno krmo, da dosežejo podobno stopnjo rasti kot živali v prosti reji. Na voljo je širok izbor komercialno pripravljene hrane za želve. Prednost hranjenja želv s komercialno hrano je priročnost, vendar podatki o prehranskih potrebah za posamezne vrste želv še niso na voljo. Namen te raziskave je bil analizirati in ovrednotiti komercialne pelete in krmo za želve. V trgovinah za živali smo od 6 podjetij kupili komercialne pelete (npeleti za vodne želve = 7, npeleti za kopenkse želve = 7) za mesojede vodne in rastlinojede kopenske želve ter drugo krmo za vodne želve (liofilizirano goveje srce, posušene vodne nevretenčarje in zamrznjene cele ribe). Zamrznjene cele ribe smo uporabili kot referenčno krmo za mesojede vodne želve. Določili smo kemično sestavo in vsebnost kalcija (Ca) ter fosforja (P). Za ničelno hipotezo smo uporabili T-test enega vzorca s podatki na etiketi in rezultate lastne paralelne analize za surove beljakovine (an gl. crude proteins, CP), ekstrakt etra (angl. ether extract, EE), surovo vlaknino (angl. crude fibre, CF), Ca in P. Oznake nekaterih peletov so bile pomanjkljive, saj so manjkali podatki o hranilnih vrednostih, Ca in P (npeleti za kopenske želve = 4 od 7, npeleti za vodne želve = 5 od 7). Podatki na etiketi so se bistveno razlikovali (p < 0,05) od rezultatov naše analize pri 13 od 14 vrst peletov. Nobeni peleti za kopenske želve niso v celoti izpolnjevali potreb živali. Zaradi neustreznega razmerja Ca : P smo kot ustrezno določili le eno izmed 7 vrst peletov za vodne želve, zaradi česar nobenih od komercialnih peletov nismo določili kot priporočljivih za glavno ali edino krmo za želve. Ključne besede: prehrana; peleti; presnovna bolezen kosti; želve
... Therefore, it was necessary to look for glucose-lowering substances to alleviate the metabolic problems caused by the high-carbohydrate feed of M. amblycephala (He et al. 2021). Betaine was a natural compound derived from animals and plants and was widely used as a food attractant in aquaculture (Kasumyan and Døving 2003;Sun et al. 2018). It had stable properties, small dosage, and low price and could be produced on a large scale. ...
A 12-week experiment was conducted to explore the effects of betaine and/or TMAO on growth, hepatic health, gut microbiota, and serum metabolites in Megalobrama amblycephala fed with high-carbohydrate diets. The diets were as follows: CD group (control diet, 28.5% carbohydrate), HCD group (high-carbohydrate diet, 38.2% carbohydrate), HBD group (betaine-added diet, 38.3% carbohydrate + 1.2% betaine), HTD group (TMAO-added diet, 38.2% carbohydrate + 0.2% TMAO), and HBT group (diet added with both betaine and TMAO, 38.2% carbohydrate + 1.2% betaine + 0.2% TMAO). The results showed that the hepatosomatic index (HSI); whole-body crude fat; hepatic lipid accumulation; messenger RNA expression levels of gk, fpbase, g6pase, ahas, and bcat; serum branched-chain amino acids (BCAAs); ratio of Firmicutes-to-Bacteroidetes; and abundance of the genus Aeromonas were all significantly increased, while the abundance levels of the genus Lactobacillus and phyla Tenericutes and Bacteroidetes were drastically decreased in the HCD group. Compared with the HCD group, the HSI; whole-body crude fat; hepatic lipid accumulation; expression levels of fbpase, g6pase, pepck, ahas, and bcat; circulating BCAA; ratio of Firmicutes-to-Bacteroidetes; and abundance levels of the genus Aeromonas and phyla Tenericutes and Bacteroidetes were significantly downregulated in the HBD, HTD, and HBT groups. Meanwhile, the expression levels of pk were drastically upregulated in the HBD, HTD, and HBT groups as well as the abundance of Lactobacillus in the HBT group. These results indicated that the supplementation of betaine and/or TMAO in high-carbohydrate diets could affect the hepatic lipid accumulation and glycometabolism of M. amblycephala by promoting glycolysis, inhibiting gluconeogenesis and biosynthesis of BCAA, and mitigating the negative alteration of gut microbiota. Among them, the combination of betaine and TMAO had the best effect.
... Understanding the molecular mechanisms of growth regulation and the genetic basis of growth variation may contribute to the genetic improvement of P. sinensis. Nowadays, many studies of P. sinensis in the fields of nutrition (Cheng, Huang, Wang, & Guanghong, 2017;Ji, Liu, Li, & Yang, 2017;Sun et al., 2018), immune (Lyu et al., 2020), and sex control (Cai et al., 2016;Sun et al., 2017) have been reported, while the molecular mechanisms involved in its growth are poorly understood. ...
The Chinese soft‐shelled turtle, Pelodiscus sinensis, is an important aquaculture species in China. Understanding the molecular mechanisms of growth regulation may contribute to its genetic improvement and lead to increases in the production. Growth rate in this species varies greatly among individuals, and the variation apparently has a genetic basis. To identify growth‐related genes and explore the molecular mechanism of its growth regulation, fast‐growing and slow‐growing turtles were selected from two growth stages, juveniles or adults, respectively, for transcriptome sequencing with liver tissue using the Illumina sequencing platform. Analyses showed that, in juveniles, 303 genes were differentially expressed, of which 217 genes were expressed at higher levels in the fast‐growing turtles. In adults, 1,093 genes were differentially expressed, of which 682 genes were expressed at higher levels in the fast‐growing turtles. Gene Ontology (GO) enrichment of differentially expressed genes (DEGs) identifies three functional groups being significantly enriched in juveniles, but 71 functional groups in adults. Kyoto Encyclopedia of Genes and Genomes enrichment analysis of DEGs in juveniles identified only one pathway being significantly enriched, the proxisome proliferator‐activated receptor (PPAR) signaling pathway, while eight pathways mostly related to fatty acid metabolism were identified in adults. These findings suggest that regulation of growth is more complicated and involves more genes and pathways in adults compared with juveniles, and metabolic or metabolic‐related genes may relate to the growth difference of P. sinensis. Some key genes related to growth were identified from another six growth‐related signaling pathways, and DEGs in GH‐IGF 1 axis genes and Jak–STAT signaling pathway might play important roles in the growth difference of P. sinensis. In addition, 73 single‐nucleotide polymorphisms (SNPs) from 23 growth‐related genes were successfully genotyped. Growth association analysis in 280 individuals revealed that 2 SNPs in 2 key genes (IGF2R and SLC27A2) were associated with growth of P. sinensis. This study provides information on key genes, SNPs, and biological processes that may be involved in growth and highlights the differentiation of growth regulation in different growth stages of P. sinensis.
... Similarly, the garlic odor of asafoetida might play an important role in leading to such a result. The bioactive compounds including disulphide, organosulfur compounds, polysaccharide, and volatile organic acids in the asafoetida might also contribute to causing L. japonicus foraging behavior (Harada and Matsuda, 1984;Harada et al. 1993;Hara 1994;Xue and Cui 2001;Pan et al. 2014;Sun et al. 2017). Our luring experimental result showed that the FAA was significantly increased when the dietary asafoetida level reached 10 g/kg, and the value reached the highest among all groups at 15 g/kg diet. ...
The study was to investigate effects of asafoetida (Ferula sinkiangensis K. M. Shen) powder on feeding attraction activity (FAA), growth performance, healthiness, and digestive enzyme activity of juvenile Lateolabrax japonicus. Six concentration levels (0, 5, 10, 15, 20, and 25 g/kg diets) were formulated for luring and feeding experiment. Results showed that asafoetida could stimulate the appetite of L. japonicus at the dietary levels from 10 to 25 g/kg; reduce the feed conversion ratio (FCR) and feed intake (FI) at 10–20 g/kg; increase the weight gain (WG) and specific growth rate (SGR) at 5–10 g/kg; increase the hepatosomatic index (HSI), body crude lipid content, serum total protein (TP) content, and lysozyme activity at 10–15 g/kg; decrease the moisture at 10–15 g/kg; and increase the serum total superoxide dismutase (T-SOD) activity at 5–15 g/kg, when compared with the control group (p < 0.05). Digestive enzyme activities including amylase (AMS) and trypsin in the intestine were significantly affected by the asafoetida powder (p < 0.05). Regression analyses between the FAA, FCR, WG, SGR, HSI, LZM, T-SOD, AMS, trypsin, and the dietary asafoetida powder levels showed that the optimal additional amount was 16.95, 13.65, 8.36, 8.15, 15.45, 9.94, 8.75, 11.77, and 7.07 g/kg, respectively, indicating that the optimal amount of asafoetida powder was located in 7.07–16.95 g/kg diet. However, combined with the significant difference analyses obtained from the current study, we would suggest the additive suitable dosage was 10 g/kg.
... taste and smell) to locate food (Velez et al., 2011). Reports presented that volatile organic acids, sugars, amino acids and sulphur-containing organic compounds had significant influence in the feeding attraction activity of aquatic animals (Hara, 1994;Harada & Matsuda, 1984;Harada et al., 1993;Pan, Xian, Kou, Wang, & Miao, 2014;Sun et al., 2017;Xue & Cui, 2001;. In this study, medicinal plant garlic powder showed significant feeding attraction activity for Japanese seabass. ...
The study was to investigate the effects of garlic (Allium sativum) powder on feeding attraction activity, growth performance and digestive enzymes of juvenile Japanese seabass, Lateolabrax japonicus (initial weight: 29.82 ± 0.24 g). Six concentration gradients (0, 5, 10, 15, 20 and 25 g/kg diets) were formulated for luring and feeding experiment. The results showed a clear attractive trend of garlic powder for L. japonicus. A 28‐day feeding experiment indicated garlic could reduce the feed conversion ratio (FCR) (p < .05). The content of the body crude lipid was significantly increased at 10–15 g/kg diet (p < .05). Digestive enzyme activities including trypsin, amylase (AMS) and lipase (LPS) in the intestine were the highest at 10 g/kg diet (p < .05). Overall, garlic powder provides a promising and effective method for Japanese seabass healthy culture by improving fish growth and digestive ability. The results of this research suggested the additive suitable dosage of garlic powder was about 10 g/kg diet.
... Betaine incorporation to SBM based diet improved feed intake relatively similar to FM. Similarly, betaine was used as a feeding stimulant in red sea bream (38), dover sole (39), European eel (40), Tilapia (31), juvenile grouper (41), and Chinese soft-shelled Turtle (42). This may indicate that betaine improved palatability of the diets which might be through stimulation of cephalic index induced by betaine smell and taste. ...
The current experiment was randomly designed in a 2×2 factorial design. Two dietary protein sources were utilized; fish meal and soybean meal; with betaine incorporation to both of them. This study aimed to determine the impact of incorporation of beta-ine into soybean meal-based (SBM) diets through its effects on growth performance, intestinal healthiness and expression of some lipid metabolism-and growth-related genes. Fish (19.84±0.20 g) were stocked in 12 aquaria and allotted into triplicate four groups (10 fish per aquarium). Four test diets were formulated to contain fish meal (FM) as a positive control, FM with betaine (FM + Betaine), SBM diet and SBM with betaine (SBM + Beta-ine), respectively. After 60 days, dietary betaine improved the growth performance of fish fed FM or SBM as revealed by higher final body weight, body weight gain and average daily gain and lower feed conversion ratio. Monitoring the whole-body composition revealed that addition of betaine to diet relatively augmented flesh protein content and reduced its fat content. In addition, betaine incorporation in diets significantly (P<0.05) increased the intestinal villi length especially in the jujenal portion as well as the numbers goblet cells. Furthermore, betaine had a downregulating effect on expression of lipid metabolism related genes, fatty acid synthetase (Fas) and lipoprotein lipase (Lpl) and up-regulating effect on insulin growth like factor-1 (Igf-1) gene in liver. It could be concluded that dietary supplementation of betaine incorporation to soybean-based diets enable nu-tritionists to substitute FM in fish diet. Also, betaine could improve growth performance, carcass quality (through increasing protein and decreasing lipid in fish) and enhance intestinal functions capability.
... RPS diet differed from RP diet by the supplementation of 1% squid paste. This account of squid paste was determined by the best diet preference of Chinese soft-shelled turtle (Sun et al., 2017). To maintain the balance of essential amino acid profile, microcapsule lysine was supplemented in the experimental diets. ...
An 8-week feeding trial was conducted to evaluate growth performance, whole-body composition, metabolism and digestion of Chinese soft-shelled turtle Pelodiscus sinensis fed with fish meal replacement by rice protein concentrate and squid paste supplementation diets. Three isonitrogenous and isoenergetic practical diets were formulated with the inclusion of 60% fishmeal (CT), 42% fish meal +18% rice protein concentrate (RP) and 42% fish meal +18% rice protein concentrate +1% squid paste (feeding attractant) (RPS), respectively. Microcapsule lysine was supplemented in RP and RPS diets to balance the amino acid profile. Turtles (initial weight 30.65 g) were fed thrice (6:00, 12:00 and 18:00) daily to apparent satiation. The results showed that growth performance in RP group showed no significant difference with that in CT group (P > .05). In addition, daily squid paste supplementation significantly improved growth performance, nutrients retention and relative feed intake (P < .05). Significantly increased activities of hepatic alanine aminotransferase as well as intestinal protease, γ-glutamyl transpeptidase, aminopeptidase N and carboxypeptidase A were also observed in RPS group (P < .05). The results suggested that rice protein concentrate could replace 18% dietary fish meal in Pelodiscus sinensis with microcapsule lysine supplementation. Besides, diet with squid paste inclusion could improve feed intake and growth performance of Pelodiscus sinensis.
Leatherback sea turtle (Dermochelys coriacea) hatchlings have previously been kept alive for over a year in captive conditions but these were the few survivors of initially larger groups. In this report, newly hatched leatherback sea turtles were randomly harvested from two nests in Thailand and successfully reared before release back to the wild. In captivity, the survival of the turtles decreased sharply during the first 4 or 5 months, and then steadied until the end of the 12-month trial. The survival of yearlings from one nest was 13.3% and from the other nest 46.7%. Their growth was exponential, reaching 1.36-3.35 kg (n = 9) at the end of program. The causes of death of the reared turtles were accidents (25.0-38.5%) and infections from water and live food (61.5-75.0%). The dietary requirements of the turtles were investigated by determining the digestibility of protein and carbohydrate in vitro, using enzymes from the digestive tracts of hatchlings that had died in an accident (70.1-92.9 g body weight). The results indicated that the most suitable source of protein was wheat gluten, followed by soybean meal, nonruminant meat and bone meal, fish meal, nonruminant meat meal, pork meal, and skimmed milk, while suitable carbohydrate sources were mashed cassava, corn, wheat flour, and alpha starch, followed by cereal meal and rice flour. Findings from the current report provide a practical protocol for head-starting leatherback sea turtles, and indicate the possible basis of an effective artificial diet for this species.
Feed additives are compounds incorporated in the diet for specific purposes other than matching up with the nutrient requirements, including the improvement of the wellbeing of the cultured organism, and enhancement of culture environment, quality of fish as a final product, and physical and chemical characteristics of the feed. A good deal of research has provided evidence on the beneficial effects of feed additives on growth performance, feed utilization ability, immune responses, and final product quality in aquaculture. Functional feed additives such as feeding stimulants and palatability enhancers, antioxidants, coloring/pigmentation agents, antimicrobial agents, organic acids, immunostimulating agents, enzymes, and hormones can promote the sustainable development of aquaculture. This chapter aims at providing an overview of the application of functional feed additives in feeds.
This study aims to investigate the effects of three feed attractants on the growth performance, body composition, biochemical indicators, liver histology, lipid metabolism and appetite of Chinese perch (Siniperca chuatsi). An eight-week feeding trial was conducted using four diets, including a basal diet of 51% fish meal without attractant (control), with 5% stickwater (SW), 5% squid paste (SP) and a 5% mixture of SW and SP a ratio of 1:2 (Mix), respectively. The results demonstrated that SW diet significantly increased the weight gain rate and feed intake (P < 0.05), while resulted in the lowest crude lipid content of whole fish and liver in Chinese perch. Dietary attractants also significantly affected the contents of serum albumin (ALB), glucose (GLU), total cholesterol (CHO), triglyceride (TG) and low-density lipoprotein (LDLC), as well as the activities of aspartate transaminase (AST) and alanine transaminase (ALT). Compared with the control diet, the SW diet significantly increased the serum superoxide dismutase (SOD) and catalase (CAT) activities (P < 0.05), while obviously decreased the activity of malondialdehyde (MDA) (P < 0.05). In addition, dietary SW significantly increased the expression of neuropeptide Y (npy) and agouti-related protein (agrp) while significantly decreased that of cocaine- and amphetamine-regulated gene (cart) and pro-opiomelanocortin (pomc) gene in the brain. As for the peripheral appetite, dietary SW reduced the expression of leptin A, while significantly increased that of ghrelin. Gene expression analysis revealed that dietary SW reduced liver lipid accumulation probably by inhibiting the lipid synthesis related gene (fas) and inducing the lipid oxidation-related gene (cpt-1).) In general, our results indicated that the supplementation of 5% SW can improve the growth performance, increase the expression of appetite-promoting genes and antioxidant capacity, and reduce liver lipid accumulation in Chinese perch.
The present study was conducted to replace fish meal with alternative plant protein sources in aquafeeds. Therefore, soybean meal (SBM), corn gluten meal (CGM), and mix of SBM + CGM were used as alternatives to fish meal (FM) with or without betaine (B) in Nile tilapia diets. Positive control diet using FM and six other diets were formulated to contain SBM, SBM + B, CGM, CGM + B, SBM + CGM, or SBM + CGM + B. Dietary B improved fish growth and body protein content in comparison to the control and equal to fish fed FM-based diet. Reduced FCR and body fat content were observed in the case of fish fed FM, SBM + B, CGM + B, or SBM + CGM + B diets. The survival rate was significantly increased in the group of fish fed SBM + CGM + B when compared to fish fed CGM diet (P = 0.013) while no significant differences were reported among the other groups (P > 0.05). Markedly increased intestinal villi length and the number of goblet cells were found in FM, SBM+B, CGM+B, and SBM+CGM+B groups (P < 0.05). Hemoglobin, blood total protein, and IGF-1 gene expression were significantly (P < 0.05) increased in fish fed FM, CGM+B, SBM+CGM, and SBM+CGM+B diets, while fatty acid synthetase (FAS) and lipoprotein lipase (LPL) were downregulated. The highest RBCs, WBCs, and globulin were observed in fish fed SBM + CGM + B diet, while the lowest number was found in the fish fed CGM diet. To sum up, B supplementation in tilapia diets acted synergistically with SBM, CGM, or both SBM + CGM to improve the growth, intestinal morphometrical indices, hemoglobin, and total protein and IGF-1 as well as decreased FCR, FAS, and LPL.
This study was conducted to evaluate the effects of dietary taurine on growth performance and feed utilization of Nile tilapia (Oreochromis niloticus) larvae. Four plant protein-based, isonitrogenous (400 g kg−1 protein), isoenergetic (19 MJ kg−1) diets supplemented with four taurine concentrations (0.0, 5.0, 10.0 and 15.0 g kg−1; designated as T0, T0.5, T1 and T1.5, respectively) were prepared. The diets were fed to triplicate groups of fish larvae (0.024 g average body weight), to apparent satiation, three times per day for 60 days. Larval growth rates and feed utilization efficiency were significantly improved with increasing supplemental taurine up to 10 g kg−1 and decreased with further taurine supplementation. The quadratic regression analyses indicated that the maximum larval performance occurred at about 9.7 g kg−1 of total dietary taurine. Fish survival was significantly lower at 15 g kg−1 dietary taurine than at other taurine levels. Body protein significantly increased, while body moisture and ash decreased, with increasing dietary taurine up to 10 g kg−1 and decreased with further taurine supplementation to 15 g kg−1. Body lipid was not significantly affected by dietary taurine concentration. A number of body amino acids (tryptophan, arginine, histidine, leucine, isoleucine, valine, alanine, glycine, threonine and taurine) significantly increased with increasing supplemental taurine up to 10 g kg−1 and then decreased with further increase in dietary taurine levels. The rest of body amino acids were not significantly affected by dietary taurine. The present results suggest that about 9.7 g kg−1 dietary taurine is required for optimum performance of Nile tilapia larvae fed soybean meal-based diets.
Analyses of the free amino acids, quater-nary amines, guanido compounds, nucleotides, nu-cleosides, and organic acids in extracts of tissues from 10 species of marine teleost fishes and 20 species of invertebrates are reported. With multidimensional scaling techniques, the relative concentrations of the above chemicals in fishes, molluscs, and crustaceans are shown to cluster into separate taxon-specific groups. The greatest differences are between the fishes and the two groups of invertebrates. Similarities are more evident between the molluscs and crustaceans where eight of the nine most abundant substances are identical: i.e., betaine, taurine, trimethylamine oxide, glycine, alanine, proline, homarine, and arginine. The major tissue components in the fishes and invertebrates are correlated with compounds previously shown to stimulate feeding behavior in 35 species of fish. Glycine and alanine are major tissue components and are also the two most frequently cited feeding stimulants in the 35 species. Molluscs and crustaceans each contain high concentrations of five of the most frequently cited stimulants (glycine, alanine, proline, arginine, and be-taine); these substances all occur in much lower con-centrations in fish. Some minor tissue components, such as tryptophan, phenylalanine, aspartic acid, va-line, and uridine 5'-monophosphate, are, however, important feeding stimulants for some fish species. Stimulants for herbivores and carnivores are often dif-ferent. Several major feeding stimulants are substances that serve as "compensatory solutes," stabilizing en-zymes and structural proteins.
A review is provided of the chemical components in tissue extracts that elicit feeding behavior in marine fish and crustaceans. For most species, the major stimulants of feeding behavior in excitatory extracts are an assemblage of common metabolites of low molecular weight including amino acids, quaternary ammonium compounds, nucleosides and nucleotides, and organic acids. It is often mixtures of substances rather than individual components that account for the stimulatory capacity of a natural extract. Recent studies using a shrimp,Palaemonetes pugio, are described in which behavioral bioassays were conducted with complex synthetic mixtures formulated on the basis of the composition of four tissue extracts. These results indicate that synergistic interactions occur among the mixture components. The neural mechanisms whereby marine crustaceans receive and code information about chemical mixtures are also reviewed. Narrowly tuned receptor cells, excited only by particular components of food extracts such as specific amino acids, nucleotides, quaternary ammonium compounds, and ammonium ions, are common in lobsters and could transmit information about mixtures as a labeled-line code. However, since physiological recordings indicate that most higher-level neurons in the brain each transmit information about many components of mixtures, rather than about a single component, it is suggested that information about a complex food odor is transmitted as an across-fiber pattern, instead of a labeled-line code. Electrophysiological recordings of responses of peripheral and central neurons of lobsters to odor mixtures and their components reveal that suppressive interactions occur, rather than the synergistic interactions noted earlier in the behavioral studies. Possible reasons for these differences are discussed. Evidence from the behavioral study indicates that the "direction" of a mixture interaction can be concentration-dependent and the synergism may occur at low mixture concentrations, while suppression may occur at high concentrations.
The fish gustatory system provides the final sensory evaluation in the feeding process. Unlike other vertebrates, the gustatory system in fish may be divided into two distinct subsystems, oral and extraoral, both of them mediating behavioural responses to food items brought in contact with the fish. The abundance of taste buds is another peculiarity of the fish gustatory system. For many years, morphological and electrophysiological techniques dominated the studies of the fish gustatory system, and systematic investigations of fish taste preferences have only been performed during the last 10 years. In the present review, basic principles in the taste preferences of fish are formulated. Categories or types of taste substances are defined in accordance with their effects on fish feeding behaviour and further mediation by the oral or extraoral taste systems (incitants, suppressants, stimulants, deterrents, enhancers and indifferent substances). Information on taste preferences to different types of substances including classical taste substances, free amino acids, betaine, nucleotides, nucleosides, amines, sugars and other hydrocarbons, organic acids, alcohols and aldehydes, and their mixtures, is summarised. The threshold concentrations for taste substances are discussed, and the relationship between fish taste preferences with fish systematic position and fish ecology is evaluated. Fish taste preferences are highly species-specific, and the differences among fish species are apparent when comparing the width and composition of spectra for both the stimulants and the deterrents. What is evident is that there is a strong similarity in the taste preferences between geographically isolated fish populations of the same species, and that taste preferences are similar in males and females, although at the individual level, it may vary dramatically among conspecifics. What is noteworthy is that taste responses are more stable and invariable for highly palatable substances than for substances with a low level of palatability. Taste preferences as a function of pH is analysed. There is a good correspondence between development of the gustatory system in fish ontogeny and its ability to discriminate taste properties of food items. There is also a correspondence between oral and extraoral taste preferences for a given species; however, there is no correlation between smell and taste preferences. Taste preferences in fish show low plasticity (in relation to the diet), appear to be determined genetically and seem to be patroclinous. Fish feeding motivation and various environmental factors like water temperature and pollutants such as heavy metals and low pH water may shift fish taste preferences. Comparisons between bioassay and electrophysiological data show that palatability is not synonymous with excitability in the gustatory system. The chemical nature of stimulants and deterrents in various hydrobionts is outlined. The significance of basic knowledge in fish taste preferences for aquaculture and fisheries is emphasised.
In aquaculture, a diet both nutritionally sound and organoleptically pleasing is essential to guarantee satisfactory intake. This has not been fully achieved with soleids (Solea solea and Solea senegalensis) because of their special palatability requirements, which are difficult to satisfy with conventional diets. Nevertheless, soleids have long been considered interesting species for aquaculture. To improve the palatability of diets for this family, various substances have been tried. Betaine has been the most effective substance by far, for all the species studied and especially for sole, reporting good results but at too high a cost. In other areas of animal production, the problems of palatability are solved with commercial flavours, which offer scope for specialisation to satisfy the most demanding organoleptic requirements. The aim of the present work is to evaluate the use of a bivalve commercial flavour as an alternative to betaine in sole diets. An ethological methodology, adapted to the feeding behaviour of sole, is developed to qualify and quantify behavioural changes when faced with experimental diets containing either this commercial flavour or betaine. Results show that the commercial flavour externally applied to feed particles performs efficiently as an attractant and as an arrestant, being able to attract the animal to the food source from some distance, provoke the ceasing of locomotion close to the food particle and promote initiation of feeding. In this step of the feeding sequence, it may be considered a viable alternative to betaine from the organoleptic point of view and economic cost. When the commercial flavour is applied internally to the feed, its performance as a stimulant, to encourage the continuation of feeding, is not distinguishable from betaine. Other factors such as time of feeding and size of fish, also assessed in the experiment, strongly influenced the level of acceptation of diets, even more than the composition of the diet itself. The distribution of feed at a time out of the endogenous rhythm of the species provoked a lower feed acceptation. Slight differences in the size of fish also affected the degree of acceptation, this being lower in the smaller fish.RésuméModification du comportement alimentaire de la sole (Solea solea) par l’addition d’un arôme commercial en tant qu’alternative à la bétaïne. En aquaculture, il est essentiel qu’un aliment soit à la fois de bonne qualité nutritionnelle et agréable organoleptiquement pour garantir une alimentation satisfaisante. Cela n’a pas encore été réalisé avec les soléidés (Solea solea et Solea senegalensis) car leurs exigences particulières, en palatabilité, sont de satisfaire la plupart des exigences organoleptiques. Le but de ce travail est d’évaluer l’emploi d’arôme de bivalve provenant du commerce comme alternative à la bétaïne dans les aliments de la sole. Une méthodologie éthologique adaptée à son comportement alimentaire est difficile à satisfaire avec des aliments conventionnels. Néanmoins, les soléidés sont considérés comme des espèces intéressantes pour l’aquaculture. Pour améliorer la palatabilité des aliments destinés aux soles, différentes substances ont été testées. La bétaïne est de loin la substance la plus efficace pour toutes les espèces étudiées et pour la sole en particulier, donnant de bons résultats mais à un coût trop élevé. Dans d’autres sites d’aquaculture, les problèmes de palatabilité ont été résolus avec des arômes du commerce, qui offrent une gamme suffisante de spécialisation pour développer, pour évaluer de façon qualitative et quantitative les changements comportementaux des soles. Les résultats montrent que l’arôme commercial appliqué en surface des granules alimentaires provoque une attirance ainsi qu’une immobilisation des soles ; en effet, elles sont attirées par la source de nourriture à partir d’une certaine distance, cessent ensuite tout mouvement de locomotion près des particules alimentaires avant de s’alimenter. Lors de cette étape de l’alimentation, on peut considérer cet arôme comme une alternative viable à la bétaïne du point de vue organoleptique et économique. Lorsque l’arôme est incorporé à l’intérieur de l’aliment, il agit comme un stimulant et encourage la poursuite de la prise de nourriture, sans effet distinct de celui de la bétaïne. D’autres facteurs sont évalués, tels que l’heure de l’alimentation ou la taille du poisson, et influencent fortement le niveau d’acceptation des aliments et même davantage que la composition de l’aliment lui-même. La distribution de l’aliment lors d’une période hors du rythme endogène de l’espèce provoque une moindre acceptation de la nourriture. De légères différences dans la taille du poisson affectent aussi le degré d’acceptation qui est plus faible chez les poissons plus petits.
The roles of nucleotides and metabolites in fish diets have been sparingly studied for over 25 years. Beside possible involvement in diet palatability, fish feeding behavior and biosynthesis of non-essential amino acids, exogenous nucleotides have shown promise most recently as dietary supplements to enhance immunity and disease resistance of fish produced in aquaculture. Research on dietary nucleotides in fishes has shown they may improve growth in early stages of development, enhance larval quality via broodstock fortification, alter intestinal structure, increase stress tolerance as well as modulate innate and adaptive immune responses. Fishes fed nucleotide-supplemented diets generally have shown enhanced resistance to viral, bacterial and parasitic infection. Despite occasional inconsistency in physiological responses, dietary supplementation of nucleotides has shown rather consistent beneficial influences on various fish species. Although nucleotide nutrition research in fishes is in its infancy and many fundamental questions remain unanswered, observations thus far support the contention that nucleotides are conditionally or semi-essential nutrients for fishes, and further exploration of dietary supplementation of nucleotides for application in fish culture is warranted. Hypothesized reason(s) associated with these beneficial effects include dietary provision of physiologically required levels of nucleotides due to limited synthetic capacity of certain tissues (e.g. lymphoid), inadequate energetic expenditure for de novo synthesis, immunoendocrine interactions and modulation of gene expression patterns. However, currently there are numerous gaps in existing knowledge about exogenous nucleotide application to fish including various aspects of digestion, absorption, metabolism, and influences on various physiological responses especially expression of immunogenes and modulation of immunoglobulin production. Additional information is also needed in regard to age/size-related responses and appropriate doses and timing of administration. Thus further research in these areas should be pursued.
For many fish, olfaction is important in food search and consumption. Amino acids are known to elicit feeding behaviour in several species. The aim of the current study was to evaluate the contribution of amino acids to the odour of a natural prey organism of the Senegalese sole (Solea senegalensis). Both whole-body macerates and substances released to the water by living ragworms (Hediste diversicolor) were fractionated by molecular weight filtration followed by solid-phase extraction (SPE), and the olfactory activity of the resultant fractions was assessed by the electro-olfactogram (EOG) in the sole. The amino acid concentrations of the macerate and water were determined by gas chromatography and mass spectrometry (GC-MS). In the macerate, the majority of odorants were small molecular weight compounds (<500 Da) which were not retained by C-18 SPE cartridges. An artificial mixture of amino acids at the same concentrations as found in the macerate had similar olfactory potency. The odorants released to the water by living ragworms were also small molecular weight compounds (<500 Da) but the majority of olfactory activity could be extracted by C-18 SPE cartridges. The concentrations of amino acids in these samples were too low to contribute greatly to its olfactory potency. These results suggest that, whilst olfactory sensitivity to amino acids may explain most of the potency of the macerate, living ragworms are releasing additional odorants other than amino acids which may be equally important in chemosensory food location in the sole. (C) 2007 Elsevier B.V All rights reserved.
Long chain n-3 PUFAs (polyunsaturated fatty acids) are found in fatty fish and in fish oils. Substantial evidence from epidemiological and case-control studies indicates that consumption of fish, fatty fish and long-chain n-3 PUFAs reduces the risk of cardiovascular mortality. Secondary prevention studies using long-chain n-3 PUFAs in patients post-myocardial infarction have shown a reduction in total and cardiovascular mortality, with an especially potent effect on sudden death. Long-chain n-3 PUFAs have been shown to decrease blood triacylglycerol (triglyceride) concentrations, to decrease production of chemoattractants, growth factors, adhesion molecules, inflammatory eicosanoids and inflammatory cytokines, to lower blood pressure, to increase nitric oxide production, endothelial relaxation and vascular compliance, to decrease thrombosis and cardiac arrhythmias and to increase heart rate variability. These mechanisms most likely explain the primary and secondary cardiovascular protection afforded by long-chain n-3 PUFA consumption. A recent study suggests that long-chain n-3 PUFAs might also act to stabilize advanced atherosclerotic plaques, perhaps through their anti-inflammatory effects. As a result of the robust evidence in their favour, a number of recommendations to increase intake of long-chain n-3 PUFAs have been made.
Taurine is a conditionally-essential amino acid that is found in high concentrations in the CNS and is essential for growth and survival of neurons. Taurine had been clinically tested in a number of diseases with variable results. In the context of neuropsychiatry, taurine was found to be altered in some neurological and psychiatric disorders and its levels affected by mood stabilizers and by antidepressants as well as anti-Alzheimer drugs. Taurine is also a common component in energy drinks and it is claimed (without scientific support) to have stimulant properties. The present study was designed to test taurine's effects in animal models of affective and anxiety disorders and to evaluate its properties as a stimulant.
Mice were treated with two doses of taurine with sub-chronic or chronic administration (for different experiments) and tested in the open field, the black/white box and the forced swim test. Taurine's possible stimulant effects were also tested in conjunction with amphetamine administration.
For the doses and schedules tested, taurine did not have an effect on measures of anxiety- or depression-like behaviors and did not act as a stimulant, neither alone nor in conjunction with amphetamine. In contrast, high dose taurine administration resulted in a transient decrease in activity.
We suggest that any effects of taurine on affective-like behavioral measures may be very subtle (if any) and that prudence is recommended in claims regarding taurine activity as a stimulant.
The evidence that omega-3 fatty acids are essential for human development and most helpful to achieve good health throughout life is clearly documented by Dr. Joyce Nettleton in her new book Omega-3 Fatty Acids and Health. Omega 3 fatty acids are produced by the plants of the land and sea. The tissues of the body require the omega-3 fatty acids for their proper functioning just as they also need the omega-6 essential fatty acids. It is probable in man's evolutionary development that there has always been the proper balance between these two groups of essential fatty acids, but in the modern era with the provision of inexpensive vegetable oils it is possible that the pendulum for increased dietary omega-6 fatty acids in the form of linoleic acid has swung too far and the intake ofomega-3 fatty acids has actualIy declined. In particular, the 22 carbon omega 3 fatty acid, docosahexaenoic acid, which has six double bonds, is important in the membranes of brain cells, heart muscle cells, the rods and cones of the retina and spermatozoa. Docosahexaenoic acid is found only in foods such as fish and other sea life, having been synthesized by the phytoplankton of the waters. An outright deficiency of omega-3 fatty acids has led to a number of distur bances in animals and human infants such as impaired vision, abnormalities of the electroretinogram, of the eye and various behavioral aberrations.
The effect of a dietary supplemented sulfonium compound, dimethyl-β-propiothetin (DMPT), on growth of marine fish (red sea bream, yellowtail, and flounder) was examined. Optimum concentrations of DMPT used for feeding tests were 5 mM (585 μg its bromide/g diet) with red sea bream and 1 mM (117 μg its bromide/g diet) with yellowtail, respectively. Dietary adimnistration of optimum concentrations of DMPT elicited a significant increase in growth of these fish: the body weight gain of the DMPT group giving about 2.5 fold increase at the 18th day with red sea bream; about 4.5 fold increase at the 13th day with yellowtail; about 1.3 fold increase at the 13th week with flounder against the body weight gain of the control group. © 1990, The Japanese Society of Fisheries Science. All rights reserved.
The present investigation was conducted to identify the feeding stimulants for juvenile ell Anguila japonica using a synthetic extract, based on the composition of the marine worm Perinereis brevicirrus. Juvenile eel showed a marked preference for a diet flavoured with the synthetic extract over an unflavoured diet.
Feeding preference tests for the diet flavoured with one of the three major fractions (amino acids, uncleotides and other compounds) in the extract showed that the amino acids fraction was most stimulatory, followed by the “other compounds” fraction including glycine betaine and maltose, while the uncleotides fraction including adenosine-5'-monophosphate was inactive or repellent. The active constitunet in the amino acids fraction was identified as the fraction glycine, alanine, proline plus histidine whose activity fraction was mixed with uridine-5'-monophosphate, the resulting mixture was found to be more stimulatory than the amino acids fraction or the complete synthetic extract.
This experiment was conducted to investigate the effects of residual salts (mainly NaCl) and free amino acids in mysid Archaeomysis vulgaris meal on the growth of juvenile Japanese flounder Paralichthys olivaceus. Five experimental diets were designed. Diet 3 contained fish meal as sole protein source. Fish meal was replaced by de-salted mysid meal at the level of 37.5% and 77.5% in diets 1 and 2 respectively. Diet 4 contained 82.0% mysid meal and diet 5 was a commercial diet. Fish with mean body weight 0.16 g (experiment I) and 1.35 g (experiment II) were fed on the above diets for 14 days, respectively. Both size of juvenile flounder (0.16 and 1.35 g) fed the 77.5% de-salted mysid meal diet showed significantly better (/><0.05) growth than that fed the 82.0% mysid meal diet. These results clearly indicated that the excess amount of salts in the diet reduced the growth of juvenile flounder. On the other hand, the best growth was shown in the fish fed the 37.5% de-salted mysid meal diet containing 81.4 mg/g free amino acids (FAA) in total nitrogen compounds. The FAA analyses of fish total nitrogen compounds showed a similar profile to 37.5% de-salted mysid meal diet. These results suggested that growth of Japanese flounder juvenile was found to be affected by dietary FAA levels in de-salted mysid meal.
Growth and thrust power of goldfish, carp, and red sea bream fed on DMPT- DMT-, and the vitamin U- supplemented diets were examined. The growth of DMPT, DMT, and the vitamin U group fish in this order was greatly stimulated with increased culture periods. This trend was similarly confirmed in the experiments determining the thrust power of these fish fed on test compounds. During the short experimental period, values of feed efficiency in the DMPT group fish were much higher than those in the other fish group. Experiments examining blood components and viscera weight from tested carp suggest that the marked enhancement of growth and thrust power resulted from the dietary administration of DMPT is closely related to increased or decreased amounts of several blood components in test fish. © 1991, The Japanese Society of Fisheries Science. All rights reserved.
The feeding stimulant activities of nucleotides-related and tryptophan-related componunds were tested on young jack mackerel Trachurus japonicus at concentrations of 1 and 5 mmo1/100 g dry diet, respectively. Effective doses of inosine 5'-monophosphate (IMP) and L-tryptophan (Trp) added to the diet on feeding activity were also examined. Of 33 compounds tested, IMP, guanosine 5'-monophosphate (GMP), uridine 5'-monophosphate (UMP), UDP, UTP, and Trp were effective. Hipoxanthine, nucleosides (inosine, adenosine, guanosine, uridine), nucleotides including adenosine 5'-monophosphate (AMP), ADP, ATP, IDP, ITP, GDP, GTP, xanthosine 5'-monophosphate, 3'-IMP, 3'-UMP, 2-deoxy-IMP, allyltio-IMP, and Trp-related compounds (D-Trp, DL-Trp, 5-hydroxy-Trp, 5-methyl-DL-Trp, tryptamine, 5-hydroxy-tryptamine, indolepropionic acid, indole-3-pyruvic acid, β-indolelactic acid, indole) were all ineffective. These results suggest that the molecular structure of 6-hydroxy-or 2-amino-6-hydroxy-purine riboside-5-phosphate is required for feeding stimulation toward jack mackerel, and that the activity of Trp was lost by a chemical modification of the molecule. The minimum concentrations of IMP and Trp needed to show the maximum effect were estimated as 0.8 and 5 mmol/100 g dry diet, respectively. © 1991, The Japanese Society of Fisheries Science. All rights reserved.
The present investigation was conducted to identify the feeding stimulants for jack mackerel Trachurus japonicus by a bioassay method using the synthetic extract, based upon analysis of jack mackerel muscle. The purified casein basal diet flavored with the synthetic extract was readily ingested by the jack mackerel, but the unflavored diet was not ingested at all. By a series of omission tests with the synthetic extract, the nucleotides group was most stimulatory in the three major groups (amino acids, nucleotides, and other bases) examined. Of the nucleotides examined, only inosine-5'-monophosphate (IMP) was highly stimulatory, but its activity was interfered with the presence of inosine, adenosine-5'-diphosphate or creatine. From these results, we concluded that IMP is the most effective feeding stimulant for jack mackerel in its muscle extract.
An 8-week feeding trial was conducted to evaluate the potential of partial replacement of fish meal with rendered animal protein blend (APB) [meat and bone meal (MBM): expanding blood meal (EBM) = 4 : 1] in the diet of juvenile Chinese soft-shelled turtle Pelodiscus sinensis. Seven isonitrogenous and isoenergetic practical diets replacing 0%, 10%, 20%, 30%, 40%, 50% and 60% fish meal protein by APB were formulated. Weight gain, feed efficiency, protein efficiency and the apparent digestibility coefficients (ADCs) of dry matter and gross energy in the experimental diets all exhibited no significant difference (P > 0.05) when dietary fish meal was replaced for 0–40%, but decreased significantly (P < 0.05) with further increasing substitution levels. However, relative feed intake, ADC of lipid as well as the contents of whole-body moisture, protein, lipid and ash all showed little differences (P > 0.05) among all the treatments. Nitrogen retention and the ADCs of protein and most amino acids all decreased significantly (P < 0.05) when fish meal was substituted by more than 30%. The results indicated that fish meal in the practical diet of juvenile Chinese soft-shelled turtle could be replaced by 30–40% using a combination of MBM and EBM without negative effects on growth performance, nutrients digestibility and body composition.
Numerous aspects of the wet acidic digestion procedure for the assay of chromic acid in a small amount of feed and excreta were examined to study the digestibility of feed by marine fishes; these examined were the spectral absorption curves of solutions prepared by the wet acid digestion of chromic oxide (Fig. 1), the stability of chromic acid solution obtained (Tables 1, 2), the effects of the amount of perchloric acid added (Table 2) and the wavelength to pre-pare the concentration-optical density curve (Fig. 2). The results of the present work showed that the following procedures were adequate for the study of digestibility. Weigh 50-100mg sample containing 1-3mg chromic oxide, wrap in a piece of filter paper and transfer to a dry 100ml Kjeldahl flask. Add 5ml of concentrated nitric acid in such a manner that it will wash down the particles adhered on the inside of the flask and allow to stand for a short period. Heat flask over a micro-electric heater which has the holes in the asbestos board covered so as to allow more heat to come in contact with the flasks. Allow the sample to digest until white precipitate is obtained (for about 20 minutes). When black particles adhere to the neck or side of the flask, wash them down by turning the flask 180°. Turn off the heater, cool the flask and 3ml perchloric acid to the digestion mixture and then reheat until green colour changes to yellow, orange or red. The reversal change in colour frequently occurs if the flasks are cooled just after the change in colour from green to yellow, because of the insufficient oxidation of the content. Therefore, the extension of digestion for 10 minutes is necessary after the colour change. Cool slightly and add about 50ml distilled water. Cool to room temperature and make up to 100ml in a volumetric flask with distilled water. Allow to stand for a few minutes to precipitate inor-ganic material. Transfer solution gently from the volumetric flask to a colorimetric tube, and read optical density at 350mμ against distilled water. The standard curve obtained by the wet acid digestion technique is expressed by the following equation;, Y=0.2089X+0.0032, where Y is the optical density at 350mμ, and X is the chromic oxide content of the sample (mg/100ml).
About 33.29 million tonnes or 36.2% of the total world fisheries catch was destined for non-food uses in 2006, either targeted for reduction into dry meal (fish meal) and oil (fish oil) for use within industrially compounded animal feeds, or used directly as animal feed in fresh, frozen, or wet processed form. However, whereas the proportion of non-food landings destined for reduction has been relatively constant since 1970 (mean +/- SD: 23.17 +/- 3.74 million tonnes), "other" non-food use landings have risen markedly from 0.90 million tonnes in 1970 (3.7% total non-food use landings) to 13.14 million tonnes in 2006 or 39.5% total non-food use landings. At present, small pelagic forage fish species, including "low-value/trash fish," form the bulk of the fisheries catch destined for non-food uses, with the aquaculture sector currently being the largest consumer. In 2006, it is estimated that the aquaculture sector consumed an estimated 23.8 million tonnes of small pelagic forage fish in the form of feed inputs, including 3.72 million tonnes used to make fish meal, 0.83 million tonnes to make fish oil used in compounded aquafeeds, and an additional 7.2 million tonnes of low value/trash fish as a direct feed or within farm-made aquafeeds.
A key concern when developing artificial aquaculture diets is their palatability. This study investigated whether the palatability of artificial diets could be improved by incorporating a small quantity of highly preferred natural foods as feeding stimulants. The preference of Tripneustes gratilla for marine plants with which it co-occurs naturally in New South Wales, Australia, was assessed in a laboratory choice feeding experiment. T. gratilla displayed significant preference for the brown alga Ecklonia radiata over five other algae and one seagrass when they were offered simultaneously. Total protein or energy in the plants was not found to account for this preference. However, T. gratilla showed no preference among E. radiata, Sargassum linearifolium and Ulva lactuca when they were dried. Three artificial diets were made by incorporating one of each of these dried seaweeds at 5% dry weight. Although not statistically significant, T. gratilla ate more than twice as much the artificial diet containing S. linearifolium compared to the control diet containing no algae in a choice feeding experiment. In a no-choice feeding experiment, T. gratilla consumed significantly more of the Ecklonia and the Sargassum diets than the control diet despite each of the diets containing approximately the same protein and energy levels. T. gratilla consumed 49 and 43% more protein, and 37 and 44% more energy, respectively, when fed with the Ecklonia and the Sargassum diets compared to the control diet. Juvenile T. gratilla grew significantly faster on a wet weight basis on the Sargassum diet than the control diet at an average increase of 2.4% per day. These results indicate that the small amounts of palatable seaweed added to the artificial diets act as feeding stimulants, increasing the acceptability of artificial sea urchin diets, boosting the protein and energy consumption, and significantly increasing the growth of T. gratilla. Moreover, the fast growth of T. gratilla achieved in this study also indicates that this species would be a good candidate for commercial aquaculture.
Trivalent oxides of yttrium and rare earth metals were evaluated as inert markers in apparent digestibility studies with salmonids in four experiments. In Experiment 1, 100 mg kg−1 of each of 15 oxides (Dy2O3, Er2O3, Eu2O3, Gd2O3, Ho2O3, La2O3, Lu2O3, Nd2O3, Pr2O3, Sc2O3, Sm2O3, Tb(III and IV) oxide, Tm2O3, Y2O3 and Yb2O3) were included in a feed fed to rainbow trout. The ratio between each marker and Yb2O3 in stripped faeces was used as an indicator of recovery. Only Er2O3, Ho2O3 and Tm2O3 had lower recoveries than the other markers. Experiment 2 compared the excretion rates of Cr2O3 and of the selected alternative markers (La2O3, Y2O3 and Yb2O3). A feed with 7.5 g kg−1 of Cr2O3 and 750 mg kg−1 of each of the other markers was fed to Atlantic salmon for a period of 1 week. Thereafter, the fish were fed with a marker-free feed, and gastro-intestinal evacuation was evaluated by comparing the marker ratios in the feed and in the faeces sieved from the outlet water of the tanks. The results did not reveal any systematic differences in evacuation among the various markers. Experiment 3 compared in vitro solubility of Cr2O3, Dy2O3, La2O3, Y2O3 and Yb2O3 in weak acid (HCl, pH 3 as in stomach contents of Atlantic salmon), weak acid neutralised with NaOH, and in water. Cr2O3 was not dissolved. Only 1.3% of Yb2O3, 22% of Y2O3, 31% of Dy2O3, and 96% of La2O3 was soluble in weak acid, but more than 99% of the dissolved markers precipitated when neutralised, and none of the markers were soluble in water. Experiment 4 compared the estimates of apparent digestibility coefficients (ADCs) of nitrogen and fat in rainbow trout when using Cr2O3, La2O3, Y2O3 and Yb2O3 as markers. The feed contained 10 g kg−1 Cr2O3 and 100 mg kg−1 of each of the other markers. Markers in feeds and stripped faeces were dissolved for the analysis with both HCl:HNO3 and H3PO4:MnSO4. Except for Cr2O3, the markers gave similar ADCs within each acid solubilisation procedure. The ADCs of fat were similar with both procedures, but the ADCs of nitrogen were 0.2% lower with HCl:HNO3 than with H3PO4. Cr2O3 was incompletely dissolved in HCl:HNO3, resulting in low ADCs. With H3PO4, no differences were seen among the ADCs obtained with Cr2O3 and the other markers. In conclusion, trivalent metal oxides, such as La2O3, Y2O3 and Yb2O3, can substitute Cr2O3 in digestibility studies with salmonids, and can be used at lower concentrations without affecting accuracy.
The feed intake of first-feeding spring chinook salmon (Oncorhynchus tshawytscha) changed significantly when the amino acid glycine or the ammonium-containing trimethylamine was added to experimental diets in a 2-week feeding trial. Glycine enhanced feed consumption, whereas trimethylamine (which occurs in rancid fish meals and oils) decreased it. This effect of trimethylamine may indicate that the fish were sensitive to it as an indicator of the freshness of their feed: this possible sensitivity may play a role in the apparent aversion that salmonids and other fish show toward highly oxidized meals and oils.
A study was conducted to determine the effects of various potential feed intake modifiers on initial feed consumption by spring Chinook salmon (On- corhynchus tshawytscha). Feed intake was immediately and significantly influenced when glycine, trimethyl- amine, or betaine was added to experimental diets. Results support the notion that glycine enhances feed intake. whereas trimethylamine and betaine decrease it. The reduced consumption of diets containing betaine, which has often been described as a feeding attractant. may have been a response to the chemical form of this compound used in this study (betaine hydrochloride) and may not occur if the free form of betaine is used.
Gustatory neural responses of the Pacific bluefin tuna Thunnus orientalis (Temminck and Schlegel) to extracted compounds of prey organisms, such as amino acids, nucleotide-related substances, organic acids and organic bases, were electrophysiologically recorded from the facial nerve supplying the anterior palate. Of the 17 amino acids tested, l-proline was the most potent amino acid at 10−2 M, and its threshold was the lowest at around 10−6 M. l-leucine, l-methionine, l-alanine, l-valine and l-isoleucine were also highly stimulatory at 10−2 M; however, the other 11 amino acids examined were not as effective or were ineffective. Thus, the gustatory receptors for amino acids of the Pacific bluefin tuna show a narrowly tuned response profile. Among the seven nucleotide-related substances tested, uridine-5′-monophosphate, inosine-5′-monophosphate and adenosine-5′-diphosphate were highly stimulatory, and their thresholds were 10−4–10−5 M. Inosine elicited a positive response at 10−2 M but its response magnitude was not so high. Organic acids l-lactic and pyruvic acids were effective at 10−2 M, but no response was elicited at 10−3 M. Among organic bases, betaine was highly stimulatory, and its response magnitude at 10−2 M is almost equal to that of l-proline at the same concentration. The threshold for betaine was determined to be at around 10−5 M. Trimethylamine oxide and ammonium chloride were ineffective.
A simple and practical method for quantification of feeding stimulation of shrimp Litopenaeus vannamei was developed using feed preference as an index of comparison. Feed preference was defined as the percentage of shrimp observed in each feeding tray. Preliminary trials were undertaken with two commercial feeds (45% protein with 5% squid meal and 40% protein without squid meal). Results indicated the following criteria were suitable for use as methodology for evaluating feeding stimulation in 5-m diameter static flow tanks: shrimp density (2.5 shrimp/m2); observational period (1 or 2 h post-addition of feed to trays), feed rate (2%), and between-trial feed rate (2%). A further investigation was undertaken to evaluate the influence of protein level and source on feed preference using a basal diet consisting of wheat flour, casein, carboxymethyl cellulose binder, and limestone, with or without krill meal as a feeding stimulant. A significant difference was shown in feeding preference for the 16% protein/4% krill meal vs. one without krill meal; however, this relationship was not shown in 45% protein feed comparisons. A second trial comparing 0, 16,30, and 45 % protein/casein-based feeds showed similar results. From these findings, it was postulated that casein, itself, also serves as a feeding stimulant at high dietary inclusion levels. A third trial comparing 16% protein/casein or wheat gluten-based feeds Indicated a delay of at least 2 h in maximum feeding preference response in feeds in which 4% krill meal was added as a feeding stimulant. It was postulated that chemical stimulants from krill meal were more slowly released in wheat gluten-based feeds. Our methodology appears suitable for evaluation of potential feeding stimulants when incorporated into low-protein casein-based or wheat-gluten-based feeds.
Two experiments were conducted to confirm and define quantitatively and qualitatively the efficiency of a mixture of attractive chemical substances (betaine, glycine, L-alanine, L-arginine, L-glutamic acid, inosine) for the weaning of 35-day-old, 120 mg weight soles. During the weaning period, a relatively high quantity (6.9% of the diet) is needed. Addition at lower levels (2.9%, 1.5%) resulted in slower growth (specific growth rate from 4.9% to 4.1%), lower survival (from 78% to 50%) and poorer feed conversion (from 2.2 to 5.5). The chemical mixture can be simplified by using only betaine, glycine and inosine, without any loss in attractive efficiency as compared to the original mixture.
An 8-week feeding experiment was conducted to determine the effect of dietary betaine levels on the growth performance and hepatic intermediary metabolism of genetically improved farmed tilapia (GIFT) strain of Nile tilapia Oreochromis niloticus (mean initial body weight: 78.3 ± 1.3 g, means ± SD). Six practical diets were formulated with the incorporation of betaine at the levels of 0 (control), 5, 10, 15, 20 and 25 g kg−1. Survival showed no significant differences among the treatments (P > 0.05). The highest and lowest weight gain (WG) and specific growth rate (SGR) were observed for fish fed the diets containing 5 and 0 g kg−1 (control) betaine, respectively. Feed intake showed similar trend with WG and SGR. In contrast, feed conversion ratio was the lowest when dietary betaine level was 5 g kg−1. In general, dietary betaine supplementation showed no significant effect on hepatic composition of tilapia. Condition factor and viscerosomatic index tended to increase with increasing dietary betaine levels from 0 to 5 g kg−1 and then decline when dietary betaine levels further increased from 5 to 25 g kg−1. In contrast, hepatosomatic index declined with increasing dietary betaine levels (P < 0.05). Dietary betaine levels significantly influenced several hepatic enzymatic activities, including succinate dehydrogenase, lactate dehydrogenase, malic dehydrogenase, lipoprotein lipase and hepatic lipase, suggesting that dietary betaine addition had significant effects on nutrient metabolism in the liver. Based on the second-order polynomial regression analysis of WG, 12.5 g kg−1 of dietary betaine level seemed optimal for genetically improved farmed tilapia strain of O. niloticus.
This study examined the long-term effects of a feeding deterrent, oxytetracycline (OTC), and a feeding stimulant, squid extract, on feed intake, growth and dry matter (DM) digestibility in Atlantic salmon, Salmo salar L. Fish were fed one of four diets for 9 weeks: 1. commercial feed formulation (basic); 2. BM (basic plus 20 g kg−1 OTC); 3. BMS (BM plus 10 g kg−1 squid extract); 4. BS (basic plus 10 g kg−1 squid extract). OTC initially reduced the palatability of the feed, but the fish seemed to become accustomed to the taste of OTC over time. Addition of squid extract to the medicated feed (BMS) seemed to mask the aversive taste of OTC, but the effect on feed consumption was of short duration. Addition of squid extract to the basic feed (BS) had no significant effect on feed intake, growth or feed digestibility. The growth of fish fed medicated diets (BM and BMS) was depressed, probably as a consequence of reduced feed digestibility. The two additives led only to temporary changes in feed acceptability, but both growth and DM digestibility were affected by OTC. Thus, we suggest that short-term studies may be inadequate to test whether deterrent or stimulant properties of feed ingredients are of practical importance in feed formulation.
A biological assay was conducted to evaluate the suitability of various leguminous seed meals and leaf meals as dietary protein sources for Asian sea bass, Lates calcarifer. In the growth experiment, fish (initial mean weight ± standard error (SE) of 3.8 ± 0.5 g) were fed isonitrogenous and isocaloric diets containing test ingredients to replace 13–18% of the diet. The same diet formulations were used in a digestibility experiment, except that 1% Cr2O3 was added as an external indicator. The growth of the control fish was comparable to fish fed leguminous seed meal-based diets, and better than those given leaf meal-based diets. The control diet had the highest apparent protein digestibility (APD) value. No significant differences were observed between the APD of white cowpea (Vigna unguiculata), green mungbean (V. radiata) and papaya (Carica papaya) leaf meal-based diets. However, the cassava (Manihot esculenta) leaf meal-based diet had the lowest APD value. The present findings suggest that white cowpea and green mungbean meals can be used as protein sources in practical diets to replace 18% of the sea bass diet without affecting their growth.
The requirement for taurine in juvenile Japanese flounder Paralichthys olivaceus was determined by feeding diets containing various levels of taurine and cystine. Test diets supplemented with 0.5, 1.0 and 1.5% of taurine or with 0.5, 1.0 and 1.5% of L-cystine were prepared. The basal diet contained 55% protein from white fish meal. These diets were fed to juvenile Japanese flounder with an initial mean bodyweight of 0.9 g (total length (TL) 48 mm) for 5 weeks. Approximately 1.4% taurine content in the diet was required for optimum growth of juvenile flounder. A positive linear relationship was noted between the content of taurine accumulated in the muscle, liver and brain and the level of taurine in the diet. However, there was no increased taurine content in tissues of fish fed the cystine-supplemented diet. In contrast, the fish fed control and cystine-supplemented diets showed higher contents of cystathionine in the tissues. The concentration of cystathionine in tissues rapidly decreased with an increase of taurine in the diet. It was also observed that for each of the dietary groups, a trace amount of taurine was excreted. These results suggest that the taurine content in the diet affects the sulfur amino acid metabolism of juvenile Japanese flounder, and indicate that juvenile flounder are unable to biosynthesize taurine from cystine.
This study was conducted to evaluate the effect on growth and feed efficiencies of the mangrove red snapper (Lutjanus argentimaculatus) when dietary fishmeal is partially replaced by defatted soybean meal (DSM). In the preliminary experiment, snapper (mean weight±SD, 58.22±5.28 g) were fed in triplicate with different dietary amounts of DSM (7.8–42.2%) that were formulated to be isonitrogenous and isocaloric. After 14 weeks, survival, growth and feed efficiencies, and hepatosomatic index (HSI) did not differ. Based on these results, a feeding trial was done using a positive control diet that contained 64% fishmeal, while the other four diets had DSM levels of 12%, 24%, 36%, and 48% that replaced fishmeal protein at 12.5%, 25%, 37.5%, and 50% respectively. All diets were formulated to have about the same protein level (50%), protein to energy ratio (P/E of 25-mg protein kJ−1), and dietary energy (19.8 MJ kg−1). These were fed to triplicate groups of snapper (mean total weight tank−1±SD, 73.19±1.2 g) at 15 fish (average weight, 4.88 g) per 1.5-t tank for 19 weeks. Growth (final average weight and specific growth rate (SGR), feed conversion ratio (FCR), survival, and HSI were not significantly different (P>0.05) while protein efficiency ratios or PERs were similar in treatments with DSM. Among snapper fed DSM, haematocrit value was significantly lower in fish fed 48% DSM and not different with fish fed 36% DSM. Whole-body crude fat of snapper fed 48% DSM was lowest while the crude protein and nitrogen-free extract (NFE) levels were highest. Histopathological analysis showed that lipid vacuoles in livers of snapper were reduced in size as dietary DSM increased. There was slight lipid deposition in the liver of snapper at 36% DSM while at 48% DSM it was excessive and hepatocytes were necrotic. There were no differences in the histology of snapper intestine. Under the experimental condition of this study, DSM can be used in snapper diets at 24% (replacing 25% of fishmeal protein) based on growth, survival and feed efficiencies, and histology of liver and intestine. For a lesser diet cost, an inclusion level higher than 24% DSM is possible with a bioavailable phosphorus supplement.
A study was conducted to determine the dietary protein requirement of the juvenile soft-shelled turtle Trionyx sinensis Wiegmann. Six isocaloric diets containing approximately 4.9 kcal g−1 of gross energy and 30%, 35%, 40%, 45%, 50% or 55% of crude protein were fed to turtles weighing nearly 5.1 g each for a 14-week experimental period (n = 3). The turtles were raised in aquaria provided with a dry area for feeding and were fed to satiation twice a day. Feed consumption and body weight were determined every 2 weeks. There was a general increase in body weight with protein concentration of feed. After 6 weeks of feeding, the turtle fed 45%−55% protein diets had significantly higher body weight than those fed 30%−35% protein diets. At 14 weeks, the body weight and the feed conversion ratio with 45% protein diet were significantly better than with 30% and 35% protein diets, but were not significantly different compared with 50% and 55% protein diets. The protein and energy retention tended to increase with dietary protein, increasing from 30% to 45% and decreasing thereafter. Survival of turtles fed diets with 50% and 55% protein was significantly higher than those fed with 30%−40% protein. The protein accretion increased with dietary protein concentration. A broken-line regression analysis of the final body weight indicated that a 46.48% dietary protein level optimally supports the performance of the juvenile soft-shelled turtle.
Nine commercial feeding attractants and stimulants for Litopenaeus vannamei were evaluated by observation of behavioral responses in animals allotted in one Y-maze aquarium apparatus. In the validation phase, fishmeal–Brazilian origin (FMBO); fishmeal–Peruvian origin (FMPO); blood meal (BM), meat and bone meal (MBM), squid meal (SM), fish oil (FO) and fish solubles (FS) were evaluated. There was also a control without stimulatory raw material. The tested materials were included at 3% in neutral gelatin pellets (wet basis). In each behavioral observation, two different ingredients were offered at the same time in equal quantities, being allotted in the end of each chamber's arm. In Phase II after system validation, the following commercial attractants were tested: 80% crude protein (CP) vegetable dried biomass (VDB80), 68% CP vegetable dried biomass + glutamate + betaine (VDB68), complex of amino acids (alanine, valine, glycine, proline, serine, histidine, glutamic acid, tyrosine and betaine) with enzymatically digested bivalve mollusk (CAA), condensed fish soluble protein (CFSP), squid liver meal (SLM), betaine (Bet), dried fish solubles–low biogenic amines (DFSLB), dried fish solubles–high biogenic amines (DFSHB) and whole squid protein hydrolysate (WSPH). Attractants were used at a 3% level wet basis with neutral gelatin, without any additional ingredient source available. The best four commercial attractants from this phase (CAA, CFSP, SLM and WSPH) were compared under 0.5% and 1.0% levels. In Phase I of the study, a higher percentage of choices were observed for FMPO and FMBO. BM and FO were the least chosen ingredients. In Phase II, the worst results were observed for Bet, DFSHB and, mainly, for VDB80 and VDB68. When two-by-two comparisons were performed, results suggested that CFSP and CAA were the best commercial attractants tested. In the last phase, both CFSP and CAA at 1.0% level were significantly more chosen by shrimp than CFSP (0.5%), SLM (0.5 or 1.0%) or WSPH (0.5 or 1.0%). At both 0.5% and 1.0% levels, shrimp spent a similar amount of time feeding on CFSP and CAA. However, only CAA was statistically better than SLM and WSPH together. Further work is required to better elucidate the chemical drivers of chemostimulation for L. vannamei for each one of the attractants tested.
The objectives of this work were to study the effects of several feeding stimulants on gibel carp fed diets with or without replacement of fish meal by meat and bone meal (MBM). The feeding stimulants tested were betaine, glycine, l-lysine, l-methionine, l-phenylalanine, and a commercial squid extract. Three inclusion levels were tested for each stimulant (0.1%, 0.5%, and 1% for betaine and 0.1, 0.25 and 0.5% for the other stimulants). Two basal diets (40% crude protein) were used, one with 26% fish meal (FM), and the other with 21% fish meal and 6% MBM. Betaine at 0.1% in the fish meal group and at 0.5% in the meat and bone meal group was used in all experiments for comparison among stimulants. In the experiment on each stimulant, six tanks of fish were equally divided into two groups, one fed the FM diet, and the other fed the MBM diet. After 7 days' adaptation to the basal diet, in which the fish were fed to satiation twice a day, the fish were fed for another 7 days an equal mixture of diets containing varying levels of stimulants. Each diet contained a unique rare earth oxide as inert marker (Y2O3, Yb2O3, La2O3, Sm2O3 or Nd2O3). During the last 3 days of the experiment, faeces from each tank were collected. Preference for each diet was estimated based on the relative concentration of each marker in the faeces.Gibel carp fed the FM diet had higher intake than those fed the MBM diet, but the difference was significant only in the experiments on betaine, glycine and l-methionine. None of the feeding stimulants tested showed feeding enhancing effects in FM diets. All feeding stimulants showed feeding enhancing effects in MBM diets, and the optimum inclusion level was 0.5% for betaine, 0.1% for glycine, 0.25% for l-lysine, 0.1% for l-methionine, 0.25% for l-phenylalanine, and 0.1% for squid extract. The squid extract had the strongest stimulating effect among all the stimulants tested.
Three trials were performed to identify feed enhancers for largemouth bass. Fish trained on dry pellets were stocked into 45 1 aquaria. Trial 1 evaluated the palatability of diets in which fish meal (FM) was replaced with 0, 20, 40, and 60% soybean meal (SM-00, SM-20, SM-40 and SM-60). Feed intake declined as dietary concentration of soybean meal increased (P < 0.01). SM-60 was used as the control and basal diet in trials 2 and 3. Trial 2 tested the following mixture of substances: (1) amino acids: alanine, glycine, proline, serine, leucine, valine, histidine, and tryptophan; (2) nucleotides: inosine and inosine-5-monophosphate (IMP-5′); (3) betaine. Dietary concentrations of chemicals were kept in the same molar ratio as in aqueous krill (Euphasia pacifica) extract. Chemical groups were tested alone or in all possible combinations. Nucleotides alone enhanced feed intake of fish by 46% compared with the control diet (P < 0.05), while amino acids and betaine were ineffective (P > 0.05). No additive effects among chemical groups were observed (P > 0.05). In trial 3, inosine and IMP-5′ were tested alone at 1400, 2800, and 5600 mg kg−1 of feed or together, each at 2800 mg kg−1 of feed. A diet with 10% fish meal (FM-10) was also evaluated. Effective dietary concentration of IMP-5′ seems to be about 2800 mg kg−1 of feed which gave a feed intake 23% higher than the control diet (P < 0.05). Dietary IMP-5′ level of 5600 mg kg−1 of feed failed to further increase feed intake (P > 0.05). Inosine was not an effective feed enhancer at the dietary levels tested (P > 0.10). No significant additive effect of inosine in a diet flavored with IMP-5′ at 2800 mg kg−1 of feed was found (P > 0.10). Feed intake was highest for fish fed FM-10 (P < 0.01), about 58% superior than feed intake for the control diet. This study showed that IMP-5′ and fish meal were effective feed enhancers, while increasing dietary concentration of soybean meal depressed feed intake of largemouth bass.
Common dentex were fed three isoprotein and isoenergetic diets to investigate the effect of partial substitution of fish meal by soy protein concentrate (0 [FM], 25 [SM25] and 40% [SM40]) in the presence or absence of taurine (T) supplementation (2 g kg− 1 on a dry weight basis) [FM + T], [SM25 + T] and [SM40 + T], on growth related parameters, muscle composition and bile salt activated lipase activity. The fish were fed twice a day by hand to apparent satiation over the course of a 12-week growth trial.
A feeding trial was conducted to evaluate the potential of replacing fish meal with processed animal by-product meals, meat meal and blood meal (4:1 ratio), in practical diets for juvenile grouper (Epinephelus coioides). Eight isonitrogenous diets were formulated to contain 45% protein and 12% lipid. Fish meal was replaced by 0%, 10%, 20%, 30%, 40%, 60%, 80%, and 100% of meat meal and blood meal (4:1) mixture (diets 1–8). The diet with 100% fish meal (diet 1) or trash fish as feed (diet 9) were used as controls. Grouper juveniles were reared in 250-l circular fiberglass tanks maintained in a flow-through seawater system. Each dietary treatment was tested in quadruplicate groups of 25 fish per tank arranged in a completely randomized design. Fish were fed the diets twice per day at a daily feeding rate of 5–6% of biomass and trash fish at 10–12% of biomass for 60 days. Percentage weight gain, specific growth rate (SGR), survival, feed conversion ratio (FCR) and body composition of grouper juveniles were measured. There were no significant differences (P>0.05) in growth performance among fish fed diets 1–7 (0–80% fish meal replacement) with those fed diet 9 (trash fish as feed). However, fish fed diet 3 had significantly higher (P<0.05) growth than those fed diet 8 (100% fish meal replacement). Survival among fish fed the experimental diets did not significantly differ (96–100%) but was significantly higher (P<0.05) than survival (90%) of fish fed trash fish. These results showed that up to 80% of fish meal protein can be replaced by processed meat meal and blood meal coming from terrestrial animals with no adverse effects on growth, survival, and feed conversion ratio of E. coioides juveniles.
Taurine has been demonstrated to be conditionally indispensable for several carnivorous fish species. Current trends in trout production include decreasing levels of fish-meal content in feeds, along with faster growing strains of fish. Taurine may be a limiting nutrient in support of elevated planes of growth for rainbow trout. A 9-wk feeding trial was conducted using a factorial treatment design with protein source (fish meal or plant) and taurine supplementation (four levels) as the main effects. The fish-meal diet series included 23% herring meal and contained 1.76% total sulfur amino acids (TSAA). The plant diet series did not contain any animal proteins and substituted protein from soy protein concentrate in place of the herring-meal protein and contained 1.5% TSAA. Taurine was supplemented at 0, 5, 10, and 15 g/kg dry diet to each of the diets in the plant series and the fish-meal series of diets. All diets were formulated to contain 43.8% crude protein and 20% lipid with an estimated physiological fuel value of 4.2 kcal/g. Fifteen fish were stocked in each of 24 tanks with a mean initial weight of approximately 26.8 g per fish. The unsupplemented fish-meal diet contained 2 g/kg taurine, and the unsupplemented plant diet had taurine levels below the detection limit of 0.1 g/kg diet. Taurine supplementation improved growth, feed conversion ratios, protein retention efficiencies, and energy retention efficiencies of fish fed the plant protein diets. No effects of taurine supplementation were observed for these response factors in fish fed the fish-meal series diets. This study demonstrates that taurine supplementation may be necessary for rainbow trout fed plant-protein-based feeds.
Two experiments were conducted to investigate the effect of dietary taurine and cystine on growth and body composition of juvenile red sea bream Pagrus major. In Experiment I, a casein-based semi-purified diet included a small amount of fish meal were supplemented with taurine at the levels of 0 (control) and 1.0%. The experimental diets in Experiment II were without fishmeal and supplemented with taurine at 0 (control), 0.5, 1.0 and 2.0% or cystine at 1.0 and 2.0%. These diets were fed three times a day for 6 weeks to fish (average body weight: 2.3 g in Experiment I and 2.5 g in Experiment II). In Experiment I, fish fed the taurine-supplemented diet showed significantly (P < 0.05) improved growth, feed efficiency and feed consumption relative to fish fed the unsupplemental diet. The whole body taurine content increased, whereas the non-essential amino acid contents decreased, in fish fed the taurine-supplemental diet compared to fish fed the unsupplemented diet. In Experiment II, the growth, feed efficiency and feed consumption of fish fed the taurine-supplemented diets, irrespective of the dietary taurine levels, were significantly higher than those of fish fed the control diet and the cystine-supplemented diets. Taurine content in the whole body increased with the dietary taurine level, while the taurine contents did not increase by the supplemental cystine. Other free amino acid contents in the taurine-supplemented diet groups followed similar trends to those in Experiment I. These results indicate that supplemental taurine to a casein-based semi-purified diet at more than 0.5% improved the growth and feed performance of juvenile red sea bream. It is also suggested that juvenile red sea bream cannot metabolize cystine into taurine
At present, small pelagic forage fish species (includes anchovies, herring, mackerel, sardines, etc.) represent the largest landed species group in capture fisheries (27.3 million t or 29.7% of total capture fisheries landings in 2006). They also currently constitute the major species group actively fished and targeted for nonfood uses, including reduction into fishmeal and fish oil for use within compound animal feeds, or for direct animal feeding; the aquaculture sector alone consumed the equivalent of about 23.8 million t of fish (live weight equivalent) or 87% in the form of feed inputs in 2006. This article attempts to make a global analysis of the competition for small pelagic forage fish for direct human consumption and nonfood uses, particularly concerning the important and growing role played by small pelagic forage fish in the diet and food security of the poor and needy, especially within the developing countries of Africa and the Sub-Saharan region.
The zebrafish chemosensory systems of olfaction, taste and solitary chemosensory cells (SCCs) are established during the first week after fertilization (a.f.). These systems presumably support the early development of feeding behaviors required as yolk supplies diminish over the same period. Yet there is no previous data reporting early chemosensory responses in zebrafish. We therefore assayed the chemosensory behavior of newly hatched zebrafish on days 3, 4 and 5 a.f. Responses were compared between fish exposed to water alone versus water containing a mixture of 12 amino acids (100 microM each) flowing through a 50 ml test chamber at 4 ml/min; computer-assisted motion analysis was used to quantify responses. Behavioral responses were first observed at day 4 a.f.; the number of fish swimming, their swimming speeds, and their net-to-gross displacement (NGDR) all increased significantly in response to amino acid stimulation. Because taste buds first appear 4-5 days a.f. and the SCCs may not respond to amino acids, these initial chemosensory responses of day 4 fish may be mediated by already established olfactory neurons. The onset of chemosensitivity in day 4 fish corresponded with an easily recognizable developmental phenotype of inactive floating; day 3 fish were inactive and resting on the bottom while day 5 fish were active and moving through the water column. The ease of identifying responsive day 4 fish suggests these animals may be useful for characterizing odorant sensitivity or developmental plasticity or for screening for chemosensory mutations.
Alternative protein sources in aquaculture diets
- D. M. III Gatlin
- P. Li