Browsing by Subject "Rainbow trout"

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Development of highly digestible fish feeds from locally available resources in Iran
(2025) Salehi, Hamed; Focken, Ulfert
In 2012, global aquaculture production (excluding aquatic plants) was 63.5 million tons, increasing to 94.4 million tons by 2022—a growth of 48%. In Iran, production rose by 62% during the same period, from 296,514 to 480,624 tons. Iran is a leading producer of rainbow trout (Oncorhynchus mykiss W.), contributing 15-21% of the global supply from 2012 to 2022. However, aquafeed, which accounts for 70% of production costs and 80% of environmental effluents, has been impacted by a decline in fish meal production in 2023. This may increase costs, especially for carnivorous species like rainbow trout, necessitating alternative protein sources. Currently, canola meal, a potential plant-based protein, is not widely used in Iran due to poor utilization by fish. Furthermore, local poultry by-products are viewed as low-quality protein sources compared to those in countries like Germany, due to a lack of processing technologies, which restricts their utilization in aquafeed industry. Therefore, some of these products like blood and feather meals are realised not comparable to fish meal in feeding rainbow trout for the aquafeed industry in Iran. Nutrient eutrophication in water bodies necessitates development of environmentally friendly aquafeed out of highly-digestible feed components, as well. Therefore, this research was conducted to assess the digestibility of various feed components, including poultry by-products such as PBM, BM, FeM, PPCon and plant-based proteins like CM and SBM, in rainbow trout. The test ingredients were incorporated into a semi-purified casein-based diet at a 30:70 ratio, with TiO₂ used as a marker, and then fed to the experimental fish. Feces were collected using the settling method in 57-liter aquaria. The apparent protein digestibility coefficients for PBM, FeM, PPCon, BM, CM, and SBM were 73%–93%, 73%–96%, 100%, 87%, 94%, and 97%, respectively. The most digestible feed components in terms of CP were chosen to create five fish-meal-free diets, with increasing levels of CM ranging from 20% to 40%, to compare with a casein-based diet in terms of growth performance and apparent digestibility in juvenile rainbow trout. Subsequently, the 35% CM diet, which achieved the least cost FCR, was slightly modified and extruded to feed fattening rainbow trout in tanks. This diet was then compared to a pelleted caseinbased diet to assess growth performance and nutrient effluents in tanks and simultaneously, the assessment of CP, CL,OMdigestibility as well as the availability of P in juvenile rainbow trout in aquaria set-up using the settling method. This extruded grow-out feed, which included 35% CM and approximately 32% highly digestible poultry by-products, proved to be comparable to the highly digestible semi-purified casein-based diet in terms of supporting growth performance and body criteria in rainbow trout. The utilization of macronutrients like CL, CP, and OM in this extruded feed was remarkably similar to that of the control feed (p>0.05). However, the P load from this practical diet was higher in the water compared to the control feed (p<0.05). This issue could potentially be addressed by lowering the phosphorus concentration in the feed for fish of that size and considering the phosphorus availability of each component used in the diet. This investigation showed that when terrestrial protein sources are properly combined to provide all essential nutrients to the fish, feeds without FM can not only promote high growth performance but also enable efficient nutrient utilization in rainbow trout. Lastly, properly processed poultry by-products can serve as valuable protein sources for the growing aquafeed industry in developing countries like Iran.
Jatropha meal and protein isolate as a protein source in aquafeed
(2011) Kumar, Vikas; Becker, Klaus
As aquaculture continues to develop, there will be an increasing need to use alternative plant proteins in aquaculture diets so that aqua eco-systems will be sustainable. Jatropha (DJKM, H-JPKM and DJPI) can be used as protein rich sources in the diets of fish and shrimp. There is a high potential for the safe use of DJKM, H-JPKM and DJPI in diets for fish and shrimp without compromising performance, provided that these ingredients are free of toxic factors. The detoxification process developed in Hohenheim is simple and robust and produces products that are safe and of good quality. Their addition to fish and shrimp diets gave excellent performance responses without any ill effects on animal health or safety. Effects on growth and nutrient utilization: ? Detoxified Jatropha kernel meal, H-JPKM and DJPI could replace 50%, 62.5% and 75% fish meal protein respectively without compromising growth performance and nutrient utilization in fish. In addition, DJKM could also replace 50% fish meal protein with no adverse effects on growth and nutrient utilization in shrimp. If the replacement levels are exceeded, the producer must examine the nutrient profile of the feeds carefully to ensure that desired production levels can be achieved and fish and shrimp health maintained. ? High inclusion (>50% fish meal protein replacement) of DJKM decreased the efficiency of conversion of feed to body mass. This could be explained partly by the increased mean feed intake which was possibly a reaction to the reduced protein retention, measured as protein efficiency ratio and protein productive value. No such effects were seen with the use of DJPI in common carp diets. ? Increased DJKM inclusion in diets caused a significant lowering of protein, lipid and energy digestibilities. No such effects were seen when DJPI was used in common carp diets. Effects on energy budget: ? Feeding DJKM and H-JPKM to common carp and Nile tilapia respectively did not change the major components of the energy budget (routine metabolic rate, heat released and metabolisable energy) compared to fish meal and soybean meal fed groups. These results revealed that dietary protein sources DJKM and H-JPKM can be efficiently utilized for growth by common carp and Nile tilapia respectively, as well as soybean meal and fish meal. Effects on expression of growth hormone and insulin-like growth factor-1 encoding genes ? As the level of DJKM inclusion increased in the common carp diet, growth rate decreased. The expression of Insulin-like growth factor-1 (IGF-1) in liver also decreased with increase of DJKM in the diet and that of the growth hormone in liver decreased. Effects on clinical health parameters and gut health: ? No mortality and unaffected haematological values suggested the fish were all in normal health. Alkaline phosphatase and ALT activities; urea nitrogen, bilirubin and creatinine concentration in blood were in the normal ranges which showed that there was no liver or kidney dysfunction. ? The measured plasma nutrient levels gave no indications of stress, but increasing the level of plant protein in the diet decreased plasma cholesterol. This may be related to high NSP content or reduced dietary intake of cholesterol. Decrease in muscle cholesterol level is also expected which could be considered good for human health. ? Histopathological evaluation of organs showed no damage to the stomach, intestine or liver of common carp or rainbow trout. Effects of Jatropha-phytate in Nile tilapia The defatted Jatropha kernel meal obtained after oil extraction is rich in protein (58−66%) and phytate (9 −11%). The phytate rich fraction was isolated from defatted kernel meal using organic solvents (acetone and carbon tetrachloride). It had 66% phytate and 22% crude protein and its inclusion in fish diets showed the following: ? Negative effects on growth performance, nutrient utilization and digestive physiology (nutrient digestibility and digestive enzymes). ? Adverse influences on biochemical entities such as metabolic enzymes (alkaline phosphatase and alanine transaminase) and electrolytes/metabolites. Salient changes include decreased red blood cell count and hematocrit content, decreased cholesterol and triglyceride concentrations in plasma and decreased blood glucose levels. The adverse effects observed may be due to the interaction of phytate with minerals and enzymes in the gastro intestinal tract, resulting in poor bioavailability of minerals and lower nutrient digestibility. The level of phytate used in the present study (1.5 and 3.0%) corresponds to 16.5% and 33.0% of DJKM in the fish diet. The DJKM at levels > 16.5% in the diet would exhibit adverse effects in Nile tilapia. Addition of phytase to the phytate containing diets would mitigate the adverse effects of at least up to 3% Jatropha phytate (or 33% DJKM) in the diet. Addition of phytase (1500 FTU/kg) in diets containing DJKM is recommended to maximize their utilization by Nile tilapia.
Nutritional evaluation of oilseed press cakes in fish nutrition with emphasis on rainbow trout (Oncorhynchus mykiss, W.)
(2019) Greiling, Alexander Michael; Rodehutscord, Markus
Fishmeal is a valuable, protein rich ingredient for fish feed. It is a source of highly digestible crude protein (CP) with a balanced amino acid (AA) profile, well digestible inorganic phosphorus (P), and a highly digestible energy content. However, its availability is decreasing owing to an increasing demand that is driven by the increased production of fish in feed-based production systems. Research has made great advances in counteracting the limited supply of fishmeal. As a result, the majority of dietary CP in fish feed is made available from oilseeds and their processed by-products. Despite the pre-existing research efforts, the continuous evaluation of feed ingredients in search for alternatives to fishmeal is key to facilitate a sustainable growth of feed-based fish production. Oilseed press cake represents a widely available source of CP. While numerous studies have evaluated the nutritional value of press cake in fish feed, the majority focused on species reared in warmwater production systems. Thus, the objective of this thesis was to add to pre-existing knowledge on press cake and its potential to replace fishmeal in fish feed, with special emphasis on rainbow trout (Oncorhynchus mykiss W.). Initially the nutrient digestibility of various press cakes (linseed, pumpkin seed, rapeseed, soybean, sunflower seed, and walnut kernel cake) was determined in rainbow trout. The press cakes differed greatly in their digestibility of crude nutrients, with CP digestibility ranging from as low as 25% (sunflower seed cake) up to 88% (pumpkin seed cake). Another digestibility experiment was conducted using rapeseed cake and sunflower seed cake whose fibre fractions were reduced using two different processing methods (sieving and dehulling of seeds prior to pressing). The fibre-reduced press cake of rapeseed and sunflower seed cake had a substantially higher CP digestibility than their unprocessed counterpart (Manuscript 1). Three growth experiments were conducted to study the effect of partial replacement of fishmeal with press cake on performance traits of rainbow trout. In all growth experiments groups of rainbow trout were fed with either a basal diet or diets in which fishmeal CP was in part replaced by press cake based on its CP digestibility that was determined in the preceding digestibility experiments. It was found that the performance traits were influenced to a different extent in dependence of the press cake and their inclusion level. Pumpkin seed cake has been shown to have the highest potential to replace substantial amounts of fishmeal of the basal diet without significantly reducing performance traits of rainbow trout. To investigate the potential utilisation of InsP-P and the formation of inositol phosphate isomers in fish two experiments were conducted. The single and interactive effects of a mineral P supplement (monoammonium phosphate; MAP; 1 g P/kg DM of diet) and an InsP6 hydrolysing enzyme (Aspergillus oryzae 6-phytase; 2800 FTU/kg DM diet) were compared between rainbow trout and Atlantic salmon (Salmo salar). For each species a digestibility experiment was conducted under common rearing conditions of each species but using the same four diets (basal diet, basal diet + MAP, basal diet + phytase, and basal diet + MAP + phytase). The faecal disappearance of InsP6 was generally low (approximately 8%) but similar between the species when the diets were devoid of either supplement. The supplementation of phytase significantly increased InsP6 disappearance in both species, but the effect was found to be more pronounced in rainbow trout. The analysis of lower inositol phosphate isomers revealed that their hydrolysis progressed to a greater extent in rainbow trout and it suggested that InsP6 is subject to a different degradation pathway in the two species. While no significant interactive effects on InsP6 disappearance were found between the two supplements for either species, the MAP supplementation slightly decreased InsP6 disappearance in Atlantic salmon but not in rainbow trout. The experiments provide an insight into the breakdown of InsP6 and the faecal appearance of specific lower inositol phosphates and suggest that the use of press cake in feed for rainbow trout seems to be more beneficial than in feed for Atlantic salmon with regards to a more sustainable use of P resources. However, more experiments are recommended to complement these initial findings to gain a better understanding of InsP6 hydrolysis in fish.