T. Gibson Gaylord

Determination of digestibility coefficients of various feedstuffs for red drum (Sciaenops ocellatus)

Abstract The availability of nutrients and energy in feedstuffs to fish may vary considerably, depending on a variety of factors including fish species, ingredient quality and processing conditions. The red drum is an emerging aquaculture species for which information concerning nutrient and energy availability is needed to more precisely formulate diets to meet their requirements and to enable effective substitution of ingredients. This study was conducted with red drum to determine apparent organic matter, protein, lipid, and gross energy digestibility coefficients and apparent phosphorus availability of the following ingredients: select (low temperature) menhaden fish meal; regular-quality menhaden fish meal, poultry by-product meal, meat and bone meal, dehulled soybean meal, cottonseed meal, and wheat. Test diets consisting of a 70:30 mixture of reference diet to test ingredient were utilized with chromic oxide as the non-digestible marker. Organic matter digestibility of ingredients generally decreased as the nitrogen-free extract fraction increased, ranging between 94% for select menhaden fish meal to 47% for wheat. Crude protein digestibility was high for most ingredients, ranging from 77% for regular menhaden fish meal to 97% for wheat, with the exception of poultry by-product meal which was 49%. Lipid digestibility coefficients ranged from 59% for poultry by-product meal to 88% for wheat. Digestible energy coefficients were generally high for the animal meals, ranging from 72% for poultry by-product meal to 95% for select menhaden fish meal however, digestible energy coefficients for plant feedstuffs were considerably lower, from 62% for wheat to 70% for cottonseed meal. Phosphorus availability from animal products was variable, with a low of 27% for poultry by-product meal and a high of 66% for meat and bone meal. Phosphorus availability from soybean meal and cottonseed meal was 47% and 40%, respectively. Wheat had the highest phosphorus availability at 79%. Data from this study indicate red drum can digest and absorb the nutrients in animal products more completely than those from plant products. This difference presumably reflects their inability to effectively digest the nitrogen-free extract portion of plant products. These data provide more precise information concerning nutrient and energy utilization of red drum and will allow ingredient substitutions in practical diet formulations based on levels of available nutrients.

Dietary protein and energy modifications to maximize compensatory growth of channel catfish (Ictalurus punctatus)

A feeding trial was conducted to evaluate influences of dietary protein and energy modifications as well as indispensable amino acid supplementation on channel catfish growth and body composition during compensatory growth. Four diets were formulated to contain 32% or 37% crude protein and were maintained isocaloric at an estimated digestible energy (DE) level of 3.0 or 3.6 kcal/g; a fifth diet was formulated to be equal to the diet containing 32% crude protein and 3.0 kcal DE/g but with the addition of an indispensable amino acid supplement at 5% of diet. Each of the five experimental diets was fed to channel catfish initially weighing 17 g for 6 weeks using either satiate feeding (control) or not feeding for 3 days then feeding to apparent satiation for the next 11 days in three cycles. Weight gain of channel catfish was significantly (P < 0.05) affected by dietary treatment with a dietary energy level of 3.6 kcal DE/g enhancing weight gain. Cumulative weight gain also was increased in fish fed diets containing 37% crude protein compared to those fed diets containing 32% protein or the diet supplemented with amino acids. Compensatory growth was observed in response to the restricted feeding regime. Feed consumption was affected by dietary protein level and feeding regime. Fish fed diets containing amino acid supplementation and 37% protein reduced cumulative feed consumption compared to fish fed the diets with 32% protein. Fish on the restricted feeding regime had reduced feed consumption compared to satiate fed fish. Feed efficiency was improved in fish fed the high-energy diets and those fed the diet with 37% protein. Fish on the restricted feeding regime also had improved cumulative feed efficiency compared to fish fed daily to apparent satiation. Hepatosomatic index at the end of the experiment was altered by feeding regime, while intraperitoneal fat ratio was elevated by feeding higher dietary energy. Composition of liver and muscle was only slightly altered by dietary treatment. Therefore, the restricted feeding regime was capable of inducing elevated growth rates during refeeding but the dietary manipulations did not augment growth rates.

Determination of relative protein degradation activity at different life stages in rainbow trout (Oncorhynchus mykiss)

Rainbow trout were reared from 5 g to approximately 400 g on a diet formulated to supply the required protein from either fishmeal or plant proteins. The fish were sampled at every weight doubling and liver and muscle samples were obtained. From these tissue samples RNA and protein were isolated and analyzed for the expression of a number of muscle regulatory and protein degradation genes and enzymatic activity for proteins involved in the caspase, calpain, and ubiquitin-proteasome pathways for protein proteolysis. Only MyoD2 showed significant differences in expression between the two diets, while no significant changes over the course of the experiment were determined for MyoD2 or the other muscle factors. For the degradation genes significant changes in expression were determined for calpain1 and calpastatin. Calpastatin also showed a significant increase in expression over the course of the experiment in the muscle of fish fed a fishmeal diet and significant decrease in expression in the liver of fish fed the fishmeal based diet. Differences in proteasome enzyme activity were found between diets in the liver and muscle of fish and for caspase-3 activity in muscle. Significant changes in activity over the course of the experiment were noted for proteasome and calpain activity in the liver and muscle. These findings suggest that diets replacing fishmeal with plant material can have some effects on protein turnover in muscle and that some degradation pathways are differentially regulated during the growth of rainbow trout.

Digestibility of Gross Nutrients by Sunshine Bass in Animal By-Products and Commercially Blended Products Used as Fish Meal Replacements

Abstract To more accurately formulate feeds for hybrid striped bass (white bass Morone chrysops × striped bass M. saxatilis), data on the availability of nutrients from feedstuffs are needed to complement information on nutritional requirements. An experiment was conducted to determine the apparent digestibility coefficients (ADCs) of protein, lipid, energy, and organic matter for an assortment of commercially available feedstuffs and blended products used as fish meal replacements. The feedstuffs tested were ring-dried blood meal, poultry by-product meal, fish solubles, and four commercially blended fish meal substitutes (PRO-PAK, PRO-PAK 65, Pro-Con 65RDB, and 60FMC). Organic matter ADCs for these products ranged from 47% for 60FMC to 130% for fish solubles, while energy ADCs paralleled these values and ranged from 48% (60FMC) to 114% (fish solubles). Lipid ADCs ranged from 49% for PRO-PAK 65 to 79% for poultry by-product meal, and protein ADCs ranged from 47% for 60FMC to 70% for fish solubles. These v...

Evaluation of Protein Reduction and Lysine Supplementation of Production Diets for Channel Catfish

Abstract A 2-year continuous production trial was conducted in earthen ponds to evaluate lysine supplementation of practical diets as a means of reducing the need for total dietary protein and limiting the nitrogenous waste production of channel catfish Ictalurus punctatus. Fingerling channel catfish with an initial weight of 34.1 g were stocked in twelve 0.04-ha ponds in early summer at a density of 24,710 fish/ha. The experimental diets consisted of three practical diets containing 30% crude protein (control), 25% crude protein, or 25% crude protein supplemented with 0.5% lysine·HCl to provide the same level of lysine as the control diet. Each diet was fed to fish in four replicate ponds to apparent satiation once a day when water temperature was greater than 15°C. Ponds were top-harvested three times during the study with a 4.1-cm-mesh grader seine to remove marketable fish. The yields of marketable fish at each harvest period were not significantly (P > 0.05) affected by diet. Following each harvest, ...

Water system is a controlling variable modulating bacterial diversity of gastrointestinal tract and performance in rainbow trout

A two-phase feeding study evaluating performance of rainbow trout and comparing luminal and mucosal gastrointestinal tract (GIT) bacterial community compositions when fed two alternative protein diets in two rearing systems was conducted. Alternative protein diets (animal protein and plant protein diets) balanced with crystalline amino acids: lysine, methionine and threonine or unbalanced, were fed to rainbow trout in two separate water systems (recirculating (RR) and flow-through (FF)) for a period of 16 weeks. The four diets, each contained 38% digestible protein and 20% fats, were fed to rainbow trout with an average weight of 12.02 ± 0.61 g, and sorted at 30 fish/tank and 12 tanks per dietary treatment. Phase 1 lasted for 8 weeks after which fish from each tank were randomly divided, with one-half moved to new tanks of the opposing system (i.e. from RR to FF and vice versa). The remaining halves were retained in their initial tank and system, and fed their original diets for another 8 weeks (phase 2). After the 16th week, 3 fish/tank were sampled for each of proximate analysis, body indexes and 16S rRNA analysis of GIT microbiota. Fish weight (P = 0.0008, P = 0.0030, P<0.0010) and body fat (P = 0.0008, P = 0.0041, P = 0.0177) were significantly affected by diet, diet quality (balanced or unbalanced) and system, respectively. Feed intake (P = 0.0008) and body energy (P<0.0010) were altered by system. Body indexes were not affected by dietary treatment and water systems. Compositional dissimilarities existed between samples from the rearing water and GIT locations (ANOSIM: (R = 0.29, P = 0.0010), PERMANOVA: R = 0.39, P = 0.0010), but not in dietary samples (ANOSIM: R = 0.004, P = 0.3140, PERMANOVA: R = 0.008, P = 0.4540). Bacteria were predominantly from the phyla Proteobacteria, Firmicutes and Bacteroidetes. Their abundance differed with more dissimilarity in the luminal samples (ANOSIM: R = 0.40, P = 0.0010, PERMANOVA: R = 0.56, P = 0.0010) than those from the mucosal intestine (ANOSIM: R = 0.37, P = 0.0010, PERMANOVA: R = 0.41, P = 0.0010). Bacteria generally associated with carbohydrate and certain amino acids metabolism were observed in the mucosal intestine while rearing water appeared to serve as the main route of colonization of Aeromonas and Acinetobacter in the rainbow trout.