Ronald G. Twibell

Effects on growth performance and body composition in Nile tilapia, Oreochromis niloticus, fry fed organic diets containing yeast extract and soyabean meal as a total replacement of fish meal without amino acid supplementation

Fish meal (FM) is the main protein source in aquaculture diets owing to its palatability and quality. Available quantities of FM have remained constant for the past several decades; however, demand has dramatically increased due to its inclusion in diets used for the global aquaculture industry. There are various alternative protein sources that can be used in aquaculture diets, with soyabean meal (SBM) being the most widely used plant protein ingredient; however, use of SBM as the sole protein source has often resulted in reduced fish growth. There is a growing segment of consumers who desire organically grown foods, and since Nile tilapia is one of the most-cultured fish in the world and has herbivorous/omnivorous feeding habits, Nile tilapia fed an organic diet may allow producers to enter this rapidly developing market. A feeding experiment was conducted to evaluate the combination of organic SBM and an organic yeast extract (YE) as complete replacements for FM. Five isonitrogenous, isocaloric diets were fed to small (0.1 g) Nile tilapia, Oreochromis niloticus, for 6 weeks. Diets contained various percentages (0%, 10%, 20%, 30% and 40%) of YE, with Diet 1 formulated to be similar to a high-quality commercial diet containing 0% YE and 20% FM. At the conclusion of the feeding trial, fish fed Diet 1 had statistically significantly (p < 0.05) higher mean final weight (3.99 g) and specific growth rate (8.48% day− 1), and a lower feed conversion ratio (1.40) than fish fed all other diets. Based upon the data, an organic diet which replaces FM with a combination of SBM and YE appears promising but further research is needed to refine formulation so as to have similar growth performance with a FM-based diet.

Altered Growth Rates, Carcass Fatty Acid Concentrations, and Tissue Histology in First-Feeding Steelhead Fed a Fish-Meal- and Fish-Oil-Free Diet

Abstract A 12-week feeding trial was conducted to evaluate a fish-meal-free, fish-oil-free diet for use with first-feeding steelhead Oncorhynchus mykiss. The marine-based control diet (marine diet) contained sardine (Sardinops spp.) meal and pollock (Pollachius virens) liver oil as the primary sources of protein and lipid, respectively. The experimental diet (terrestrial diet) contained only terrestrial sources of protein (poultry by-product meal, blood meal, canola, corn gluten, and wheat gluten) and lipid (canola oil and flaxseed oil). Each diet was administered to five replicate groups of first-feeding fry. At the conclusion of the feeding trial, fish that were fed the marine diet exhibited significantly higher weight gain and feed efficiency than fish that were given the terrestrial diet. Survival was not significantly affected by dietary treatment. However, fish that received the terrestrial diet exhibited significantly lower hemoglobin concentration and percent packed cell volume. Histological exami...

Evaluation of Commercial Diets for First-Feeding Spring Chinook Salmon

Abstract In 2006, Bio-Oregon, Inc., the only commercial producer of cold-extruded moist diets (∼20–27% moisture) formulated for salmonids, announced that it would discontinue production of this diet line. One of these diets, BioDiet starter (19.5–21.5% moisture) was the primary feed used in many hatcheries that produce Chinook salmon Oncorhynchus tshawytscha. Thus, a feeding trial was conducted to identify an alternative starter diet for spring Chinook salmon. Five commercial diets were evaluated: Skretting BioVita (<10% moisture), EWOS Micro (<10% moisture), Rangen Starter (<10% moisture), Rangen Soft-Moist (14–17% moisture), and Silver Cup Soft-Moist (<13% moisture). Each dietary treatment was fed to quadruplicate groups of 200 randomly selected first-feeding fry reared in fiberglass tanks. Initial weight of the fish averaged 0.34 g/fish. The flow-through water supply was 12°C throughout the 8-week feeding trial. At the end of the study, fish fed Skretting BioVita exhibited significantly higher (P < 0.0...

Influence of Lineage, Broodstock Conditioning, and Hormone Injection on Gila Trout Reproductive Success and Egg Fatty Acid Composition

Abstract Successful reproduction of captive-reared fishes depends on hatchery practices and proper broodstock nutrition. Nutrient requirements and environmental conditions stimulating reproductive development are unknown for many threatened and endangered species and may differ between lineages within species. Accordingly, prior to spawning, Main Diamond Gila Trout Oncorhynchus gilae broodstock were exposed to different thermal cycles and hormonal injection to improve reproductive success. Additionally, egg fatty acid composition and hatching success of Main and South Diamond Gila Trout were evaluated to determine the extent of phenotypic differences between lineages. Thermal conditioning of broodstock accompanied with injections of exogenous luteinizing hormone releasing hormone analog (LHRHa) prior to spawning improved progeny survival over historic hatchery means as well as means for broodstock reared in raceways at constant temperatures without LHRHa. Egg n-6 fatty acid content appears to be associate...

Evaluation of Dietary Lipid Sources for the Juvenile Lost River Sucker

AbstractThe establishment of a propagation program is among the recommended actions of the U.S. Fish and Wildlife Service recovery plan for the endangered Lost River Sucker Deltistes luxatus. As an initial step in diet development, a feeding trial was conducted to identify appropriate dietary lipid sources to feed juvenile Lost River Suckers at a rate of 0.47 g/fish. Six dietary treatments were produced by adding the following to a basal diet: (1) marine fish oil (Fish) as a control, (2) flaxseed oil (Flax), (3) soybean oil (Soy), or a 1:1 mixture of (4) fish and flax oil (Fish/Flax), (5) fish and soy oil (Fish/Soy), or (6) flax and soy oil (Flax/Soy). At the conclusion of the feeding trial weight gain of fish fed the control diet (Fish) was not significantly different than that of fish fed the other dietary treatments. However, weight gain of fish fed Soy was significantly higher than that of fish fed Fish/Flax. Whole-body lipid was significantly higher in fish fed Soy than in fish fed Fish, Flax, Fish/F...

Evaluation of First Feeds for Larval Lost River Suckers

AbstractThe Lost River Sucker Deltistes luxatus is endemic to the Klamath Basin in southern Oregon and northern California. Population declines led to listing this species as endangered in 1988. Its native habitat has been greatly reduced and degraded putting their future in question. If this species is to be reared in captivity to prevent extinction, the development of culture methodologies is necessary. Successful initial feeding methods are one of the first areas of culture that need to be developed. Lost River Suckers begin feeding during the larval life stage. Larval fish often require live prey at the onset of feeding; however, it may be possible to start larvae on formulated microdiets. We investigated the use of live Artemia and two commercial microdiets (Hikari and Otohime brands) as first feeds over the course of a 41-d feeding trial. Starting on day 21 of the trial, feed sizes were increased, and the Artemia-fed fish were offered a commercial microdiet (Otohime) while being co-fed Artemia throu...

The Effects of a Transition Diet on the Smoltification of Chinook Salmon

AbstractTransition diets, often supplemented with salt and other additives, have been used to prepare Pacific salmon Oncorhynchus spp. being moved directly from freshwater to saltwater net pens for aquaculture production. However, the use of transition diets to prepare hatchery-reared salmon released into freshwater prior to out-migration to the ocean has shown mixed results. We compared the physiological (size, condition factor, Na+,K+-ATPase [NKA] enzyme activity, survival during a saltwater challenge) and nutritional (proximate composition, fatty acid profile) condition of juvenile Chinook Salmon O. tshawytscha that were fed either a standard hatchery feed or a commercially available transition diet for the final 6 weeks of hatchery rearing to determine whether the transition diet altered smolt condition. At release, NKA activity of fish fed the transition diet was higher than that of fish fed the control diet, though survival during a saltwater challenge was similar between groups. Differences were se...