Two experiments were conducted to evaluate the effects of adding an organic acid salt blend (OAB, 10g acid moiety kg−1 of a mixture of sodium formate and butyrate, ratio 2:1) and plant proteins ...(soybean meal and pea protein concentrate) to diets for rainbow trout (Oncorhynchus mykiss) reared in freshwater. The experiments were designed according to a 2×3 factorial design, where the factors were: two protein sources (fish or plant meals) and three methods of applying OAB to the diets (none, before, or after extrusion). In Exp. 1, duplicate groups of 0.95-kg trout were used to assess the effect of OAB on digestibility of nutrients. The supplementation of OAB before extrusion in the plant protein-based diet significantly reduced the digestibility of dry matter, organic matter, crude fat, and most amino acids. Supplementation of OAB after extrusion reduced the digestibility of crude fat both in the fishmeal and plant protein-based diets. Partly replacing fishmeal with plant proteins reduced the digestibility of dry matter, organic matter, crude fat, phosphorous and several amino acids. In Exp. 2, triplicate groups of 0.23-kg trout were used to evaluate the effect of OAB on growth performance and gut health. Supplementation of OAB in both fishmeal and plant protein-based diets before extrusion significantly increased feed conversion ratio, and middle intestine to body weight ratio. Partly replacing fishmeal with plant proteins significantly increased feed conversion ratio. There was no effect of dietary treatment on morphology in the distal intestine. In conclusion, supplementing diets with a sodium formate and butyrate blend did not improve growth rate or feed utilization of rainbow trout. Replacing 36% fishmeal with a combination of soybean meal and pea protein concentrate negatively influenced the nutrient digestibility and feed conversion ratio, but did not affect the growth rate of rainbow trout.
The aim of this study was to investigate how diets containing partially deshelled or whole krill meals affected growth, digestibility of main nutrients, faecal excretion of minerals, fluoride ...accumulation, and organ indices and health parameters in Atlantic salmon (
Salmo salar). Three extruded diets were fed for 100
days to salmon with an average weight of 550
g, distributed into 9 tanks equipped with flow through sea water. The dietary treatments comprised a control diet based on high-quality fish meal (FM) and two experimental diets where the FM was substituted with either partially deshelled krill meal (PDKM) or whole krill meal (WKM). Shell removal reduced the chitin content from 28 to 8
g
kg
−1 dry matter (DM), while fluoride was only reduced from 940 to 631
mg
kg
−1 DM.
Growth rate for fish fed WKM was significantly lower than for salmon fed control diet whereas the PDKM diet did not appear to alter growth during the first feeding period. Digestibility of lipid tended to be higher for PDKM and lower for WKM compared to the FM control. No significant difference was seen for digestibility of nitrogen, but fish fed the FM diet had higher digestibility of threonine, serine, glutamine, histidine and lysine compared to fish fed the WKM diet. No major differences in plasma were seen for triacylglycerols, free fatty acids, glucose, total protein, albumin, globulin, urea, and total bilirubin. Trypsin activities in the pyloric and mid intestine were lower in fish fed the WKM diet compared to FM. Bile acid concentration in the pyloric intestine were significantly lower in fish fed the WKM diet compared to FM and PDKM. Fish fed both diets containing krill meal had signs of mild to moderate nephrosis. To conclude, PDKM could successfully replace FM as a sole protein source for Atlantic salmon, whereas the WKM slightly reduced growth rate compared to the FM and the PDKM diet.
The aim of this experiment was to determine the optimal inclusion level and ratio of lupin (LPC) and pea protein concentrates (PPC) in multiple essential amino acid-supplemented diets for rainbow ...trout (Oncorhynchus mykiss). Nine extruded diets, including eight plant protein based diets formulated using four mixtures of LPC and PPC (L/P ratio, 3:0, 2:1, 1:2 and 0:3) with two dietary inclusion levels (300 or 500g plant protein kg−1 dietary protein) and one diet with LT fish meal as the sole protein source (FM diet) were used. Duplicate tanks of 58g trout reared in 8.2°C water were fed the diets for 62days, followed by a 20-day digestibility experiment. No mortality occurred, an average weight gain (WG) of 181g and an average feed conversion ratio (FCR) of 0.72g ingested dry matter (g gain)−1 was obtained. Plant protein inclusion level or L/P ratio did not significantly affect feed intake, WG, body composition (except ash), or retention of nitrogen (N) or energy. High inclusion of plant protein concentrates resulted in significantly higher FCR, apparent digestibility (ADC) of N, lipid, methionine (Met) and tryptophan (Trp) and plasma triacylglycerols level than low inclusion. However, ADC of dry matter, starch and histidine, whole body ash content and plasma cholesterol levels were reduced. The diets with the highest L/P ratio (3:0) resulted in significantly higher FCR than the other diets with less LPC. ADC of starch was reduced by increasing dietary LPC. The diets with the most PPC (L/P ratio=0:3) inclusion resulted in significantly higher ADC of dry matter, N, starch and energy than other diets with less PPC, and higher plasma cholesterol level than diets with L/P ratio of 3: 0 and 1:2. Lipid digestibility was reduced by increasing LPC at the 500gproteinkg−1 dietary protein inclusion level, but not for 300gkg−1. The diet with most LPC also resulted in lower trypsin activity in mid-intestine digesta than diets with less LPC and the FM diet. No intestinal inflammation was observed for any of the dietary treatments. However, trout fed the diet with highest inclusion of PPC tended to have a slight decrease in mucosal fold height and a slight increase in fold fusion. In conclusion, any combination of LPC and PPC with essential amino acid-supplementation can be efficiently used when total plant protein inclusion is limited to 300gkg−1 crude protein in extruded diets for rainbow trout. At higher inclusion, PPC appears to be a preferable source of protein.
► Rapid growth and low FCR with lupin and pea protein in feed for rainbow trout. ► Higher digestibility of amino acids in plant protein diets than from LT fish meal. ► Any mixture of lupin and pea proteins can be used at 300gkg−1 protein replacement. ► Pea protein concentrate is preferable to lupin concentrate at high inclusion in feed.
Early sexual maturation of male chinook salmon (maturation 1 to 4 years prior to females in the same age class) results in reduced effectiveness of stock enhancement programs and a financial loss to ...the salmon farming industry. Previous studies in Atlantic salmon have shown that the age of maturity in males is affected by growth and/or body energy stores, but the relative roles of these two factors are not well understood. Therefore, an experiment was designed to determine when spermatogenesis was initiated, to characterize the endocrine changes during the onset of puberty in male salmon, and to determine if the level of whole-body lipid affects the incidence of early male maturation in a wild stock (Yakima River) of 1+ spring chinook salmon. Fry were fed a commercial diet from February until August and were then divided into groups of 320 fish (mean weight, 5.6 g) and fed one of five experimental diets (two replicate groups/diet) containing 4%, 9%, 14%, 18% or 22% lipid and 82%, 77%, 73%, 69%, or 65% protein for 13 months. Fish were reared on natural photoperiod and ambient temperature (6°C to 16°C), and pair-fed to a level based on the tank with the lowest feed consumption. Fish were weighed monthly and sampled to determine body composition, pituitary follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels, plasma insulin-like growth factor I (IGF-I) levels, and stage of gonadal development.
Throughout the experimental period the mean fish weight was similar among treatment groups. However, from December through the end of the experiment in the following September, maturing males were significantly larger than nonmaturing fish. Initial lipid levels in 0-age experimental fish were near 6%, which is similar to wild fish of the same stock and age captured in the Yakima River during August. Fish fed diets containing more than 4% lipid increased in whole-body lipid content during the first 2 months of feeding and then maintained at relatively constant levels during the course of the experiment. Whole-body lipid levels for the dietary treatment groups averaged 5.6%, 7.1%, 8.2%, 9.4%, and 9.6% from October through the following September.
Based on histological examination of the testes of experimental fish, type B spermatogonia and primary spermatocytes were first observed in some of the yearling males during November. These were designated maturing males. Pituitary FSH levels were significantly higher in maturing than nonmaturing males at this time and for the remainder of the study. Pituitary FSH levels increased as spermatogenesis proceeded in maturing fish, whereas pituitary LH levels increased in maturing 1+ males only during July and August, when testes were in late stages of spermatogenesis and in September during spermiation. Plasma IGF-I levels were significantly higher in maturing males than nonmaturing fish from December through the end of experiment. Since maturing males were significantly larger than nonmaturing fish of both sexes from December through September, the difference in IGF-I levels could be due to differences in growth or due to maturation.
The percentage of maturing males was significantly influenced by whole-body lipid, increasing from 34% in fish fed the 4% lipid diet to 45% in fish fed the 22% lipid diet. These data suggest that whole-body lipid levels influenced the incidence of maturation of male spring chinook salmon. In addition, both endocrine and histological indicators suggest that maturation was initiated in males approximately a full year prior to the time the fish will spawn.
The objectives of this work were to evaluate how dietary soybean meal (SBM) or a soy meal made by bioprocessing the SBM (BPSBM) to remove anti-nutritional factors affected hydrolytic capacity, amino ...acid absorption, intestinal morphology, and microflora along the intestinal tract of Atlantic cod at two life stages. Three fish meal based standard cod diets were formulated to contain no soy (FM control), 25% SBM, or 22% BPSBM. Prior to sampling the diets were fed to duplicate groups of 0.5 kg (1-year old) and 1.7 kg (2-year old) cod for a period of 3 months, and the groups reached 0.9 and 2.5 kg, respectively. Digesta was then sampled from different intestinal sections for analyses of trypsin and amylase activity as well as absorption of amino acids, nitrogen, and sulphur. Gastrointestinal sections were sampled for measurements of relative weight (kg
−
1
body weight), and tissues from these sections were sampled for analyses of brush border enzyme (alkaline phosphatase (ALP), leucine aminopeptidase (LAP), and maltase) activity and histological examination. Microflora was sampled from both digesta and the intestinal wall. The SBM diet stimulated relative growth of all gastrointestinal sections except the distal intestine in both age classes. Relative growth of the pyloric intestine was also stimulated by BPSBM. The pyloric caeca and the upper mid intestine were found to be the major sites for enzymatic hydrolysis of protein and starch and for amino acid absorption. Dietary SBM and BPSBM did not alter the activity of trypsin and LAP, but the activity of these enzymes in the proximal intestine was affected by age, being higher in 1-year old than in 2-year old cod. The rate of amino acid, nitrogen, and sulphur absorption along the gastrointestinal tract was not affected by SBM, but was slowed by BPSBM. Dietary SBM or BPSBM did not alter the morphology of the intestinal mucosa in any sections of the cod intestine. The distal-most structure of the intestine, a compartment with inlet and outlet (anus) valves, showed very high microbial colonisation in the mucosal brush border. Inclusion of SBM in the diet changed the intestinal microflora, increasing the population level of transient bacteria in the pyloric and mid intestine, but reducing the population level of adherent bacteria throughout the intestine. To conclude, Atlantic cod appeared to have a robust and flexible digestive system able to adjust to high dietary levels of soy protein meals.
The aim of this experiment was to define the optimal mixtures of plant protein concentrates in an extruded, fish meal free diet for rainbow trout. Three essential amino acids (EAA) and ...taurine-fortified plant protein mixtures (P-MIX, C-MIX, and S-MIX) were prepared by mixing four plant protein concentrates (pea protein concentrate (PPC), canola protein concentrate (CPC), potato protein concentrate, and soy protein concentrate (SPC)). Seven plant protein based diets were formulated based on a mixture design using P-MIX, C-MIX, and S-MIX alone (the PPC, CPC or SPC diets) or in combinations (the P+C, P+S, C+S, P+C+S diets) to provide >95% of the dietary protein. The diets were supplemented with 5% krill products as attractant. One fish meal based diet, which acted as a reference diet, used LT-fish meal as the sole dietary protein source (FM diet). All diets were tentatively balanced to contain equal amounts of digestible protein (400gkg−1) and digestible energy (21MJkg−1). Each diet was fed to two tanks of 61g rainbow trout reared in 9°C water for 72days. No significant differences (P>0.05) were seen in weight gain. Dietary plant protein treatments that gave significantly higher values than the FM diets were: feed intake for the CPC and SPC diets; feed conversion ratio (FCR) for all diets, except for P+C and P+C+S; apparent digestibility (AD) of phosphorus (P) for all diets; AD of Arg and Met for the SPC diet; whole body crude protein content for the SPC and P+S diets; retention of dietary P intake for all diets, except for the SPC and P+S diets; N intake, metabolic N loss and energy intake per kg gain for all diets; nitrogen (N) retained in growth per kg gain for the SPC and P+S diets; fecal N loss per kg gain for the CPC diet; fecal energy loss per kg gain for the PPC, CPC, SPC and C+S diets. Significantly lower values than the FM diets were obtained for: AD of N for the CPC diet; AD of lipid for the SPC diet; AD of energy for the CPC, SPC, and C+S diets; AD of all EAA, Cys, and total amino acids for the CPC diet; retention of dietary and digestible N intake for all diets; dietary energy intake per kg gain for the CPC, SPC and C+S diets; P intake and fecal P excretion per kg gain for all diets. Using the combination of P-MIX and C-MIX resulted in the highest retention of digestible N. A combination of P-MIX and C-MIX led to the most efficient feed conversion. AD of N and individual amino acids were highest when S-MIX was used alone. The most efficient AD of lipid and energy were obtained by a combination of P-MIX and S-MIX. Using C-MIX alone supported the highest AD and retention of P, and whole-body concentrations of ash, P, Ca and Mg, due to CPC being dephytinized. Retention of dietary N was most efficient when a combination of P-MIX and S-MIX was used, while retention of digestible N was most efficient for a combination of P-MIX and C-MIX. In conclusion, the mixture model proved useful for optimizing combinations of plant protein concentrates in a fish meal-free diet for rainbow trout.
► Similar growth in trout with 95% dietary plant protein as with LT fish meal only. ► Mixture modeling is useful to optimize diet composition. ► Combining dietary plant proteins is more efficient than single ingredient. ► Pea, Canola, and potato proteins combined gave best feed utilization. ► Soy protein concentrate was preferred for maximum protein digestibility.
A study was conducted to obtain more information about optimal macronutrient ratios in diets for Atlantic cod (
Gadus morhua). Fourteen extruded diets based on fish meal, fish oil and maize starch ...were fed to cod (initial weight 77 g) in 150-L tanks (
n
=
2–4) in an incomplete factorial design. The diets contained approximately 49, 54, 58 or 63% crude protein and 11, 16, 20, 23 or 28% crude lipid (6–23% starch). The growth trial was stopped during the third week because of a parasite attack, but the fish continued to receive their respective experimental diets. Seven weeks after the original start, the growth trial was re-started. Over the following 8 weeks, the fish grew from a mean weight of 121 g to final weights ranging from 196 to 261 g, but there was no significant effect of dietary protein or lipid levels on growth rate. The feed efficiency ratio (FER) was negatively correlated with the dietary starch concentration and positively correlated with the dietary lipid concentration. FER was significantly higher for cod fed the diets containing 20% or more lipid. Protein digestibility was slightly higher in the 63% protein diets than in those containing 58% protein and higher in the diets containing 23 or 28% lipid than in those containing 11% lipid (
P
<
0.05). The hepatosomatic index (HSI) increased during the total 15-week period from an initial level of 6.4% to a range of 7.4 to 13.2% and was significantly affected by an interaction between dietary protein and lipid concentrations. The dietary protein:energy ratio accounted for 69% of the variation in HSI. Nitrogen retention was significantly affected by the interaction between dietary protein and lipid levels. To remove the effect of the liver growth in the cod, the growth rate of the carcass was calculated. In the cod fed the diets containing 58% protein, carcass growth rate was greater than in those fed the 49% protein diets. At a dietary lipid level of 20%, which was optimal for FER, a comparison of the diets containing 49 or 58% protein showed no significant differences in feed intake, whole body or carcass growth rates, protein digestibility or HSI. The 49% protein diet led to greater nitrogen retention in the cod and is less expensive than the 58% protein diet and, thus, is recommended as the most optimal diet for cod under 300 g.
The long-term goal of this research program is to develop and validate bioenergetic models for juvenile salmonid production oriented toward practical hatchery applications. As an initial step toward ...attainment of this goal, the efficacy of the model was evaluated by comparing model simulations with published data for the growth of a wild strain of coho salmon and a domestic strain selected for its rapid growth characteristics. Model simulations were consistent with the observed growth for each strain when the consumption rate model coefficient was adjusted to account for differences in the stomach size. In an independent study, the growth and proximate composition of juvenile Chinook salmon were measured in response to high and low lipid diets supplied at two different feeding rates. Model simulations were closely comparable to these data when the model coefficients for consumption and apparent respiration rate were adjusted to account for ration and body lipid content. These insights and the successful simulation of measured growth data for eight different combinations of ration, food composition, and coho strain are useful and necessary steps needed to support the development of credible production-scale management models for juvenile salmonid fish production and waste by-product generation from aquaculture and mariculture activities.
•We applied a bioenergetic model for salmonid production to published data.•We compared model simulations with lab feeding studies for coho and Chinook salmon.•Model consumption rate for two coho salmon strains varied with stomach size.•Model respiration rate for Chinook salmon was adjusted for body lipid content.•Simulations matched growth data for eight combinations of ration, diet, and strain.
This experiment was done to study the effects of dietary soybean meal (SBM) and inulin (a prebiotic) on the capacity for digestive hydrolysis and amino acid absorption by Atlantic salmon, and how a ...dietary supplement of the broad-spectrum antibiotic oxytetracycline (OTC) modulated these responses. A control diet (FM) was made from fish meal, fish oil and extruded wheat. Two similar diets were made with 250 g soybean meal (SBM) or 75 g inulin kg
−
1
. Each diet was made with or without a supplement of 3 g OTC kg
−
1
. All six diets contained yttrium oxide for estimation of apparent nutrient absorption. Each diet was fed to two groups of 172 g salmon kept in 1 m
2 tanks with 9 °C saltwater for 3 weeks. Intestinal organs were then sampled and weighed. Gastrointestinal tracts (GIT) were sectioned for analyses of brush border alkaline phosphatase (ALP) and leucine aminopeptidase (LAP) activities. Tissue from the distal intestine (DI) was also fixed for histological examination. Digesta from the different sections were freeze dried for estimation of trypsin and amylase activities, and of apparent absorption of amino acids (AA), nitrogen (N), and sulphur (S). About 85% of the trypsin activity, 70% of the amylase activity, 85% of the ALP activity, and 82% of the LAP activity were found in the proximal (PI) and mid (MI) intestine of fish with functional DI, and the absorption of AA, N, and S was quantitatively completed in the MI. Dietary OTC resulted in lower relative liver weight, but apart from increased ALP and LAP activities in DI when feeding OTC in combination with inulin, OTC did not modify the responses to dietary SBM or inulin. Dietary SBM resulted in lower relative liver weight, and induced pathomorphological changes in the DI mucosa, thus lower the ALP and LAP activities in the DI. SBM also stimulated absorption of AA, N, and S in the PI, but at the same time increased the activities of trypsin and amylase in the DI, indicating reduced re-absorption and increased faecal losses of these endogenous enzymes. Dietary inulin did not damage the DI, and stimulated intestinal growth and higher relative mass of the GIT. Inulin without OTC did not affect the hydrolytic and absorptive capacity of the salmon GIT.
