Harold Phillips

Dietary calcium, phytate and zinc interactions in channel catfish

Abstract Interactions among dietary calcium, phytate and zinc were investigated by feeding eight purified egg-white diets containing 0.5 or 2.0% Ca, 0.5 or 1.5% phytate and 20 or 200 mg Zn/kg in a factorial arrangement to triplicate groups of fingerling channel catfish (Ictalurus punctatus) in aquaria for 12 weeks. A significant (P

Dietary protein requirement of juvenile golden shiners (Notemigonus crysoleucas) and goldfish (Carassius auratus) in aquaria

Abstract Two feeding trials were conducted to establish the dietary protein level required to optimize weight gain, feed efficiency, survival, protein efficiency ratio (PER) and whole-body protein of juvenile golden shiners and goldfish. The individual average initial weight of both golden shiners and goldfish was 0.2 g. Semipurified diets contained 21.2, 25.3, 28.9, 31.1 or 34.5% protein from a combination of fish meal and casein. Estimated available energy of the diets averaged 2.8 kcal/g, based on digestible energy values of these feed ingredients for catfish. Golden shiners and goldfish were raised in flow-through aquaria with a water temperature of 25±2°C for 6–8 weeks. Weight gain and feed efficiency were best in fish fed diets containing 28.9% protein or more in all experiments. The PER values declined in fish fed diets containing more than 28.9%. Survival was independent of diet, and whole-body protein was not a reliable indicator of protein requirement. There were no differences in requirements attributable to fish species. Quantitative protein requirements of golden shiners and goldfish were similar to those reported for other warmwater species. The calculated dietary energy/protein ratio that supported best performance of these baitfish (9.7 kcal/g) was similar to that reported for other warmwater species. Because golden shiners and goldfish fed diets containing 29% protein showed optimal performance in the absence of natural food, the use of feeds containing 32% protein in pond culture of these fish does not seem warranted, especially because they derive significant amounts of nutrients from pond biota.

Effects of various levels of dietary copper and zinc on channel catfish

Furified egg white diets containing 1 or 20 mg Cu/kg and 20, 100 or 200 mg Zn/kg in a factorial arrangement were fed to triplicate groups of fingerling channel catfish (Ictalurus punctatus) in aquaria to investigate possible interactions between dietary copper and zinc. At the end of the 12-week feeding trial, weight gain and feed efficiency values of catfish fed the various diets were similar. Dietary zinc had a significant (P < 0.01) effect on hematocrit, which was generally reduced at higher levels of zinc intake. However, such a response was not observed in hemoglobin from fish fed the various diets. Dietary zinc also had a significant (P < 0.01) effect on catfish bone zinc and liver iron, but not liver zinc concentrations. Hepatic copper concentration and activities of heart cytochrome c oxidase and liver copper-zinc superoxide dismutase (SOD) were significantly (P < 0.05) reduced in catfish fed 1 mg Cu/kg compared to those fed 20 mg Cu/kg, while manganese SOD showed a compensatory increase in activity at low copper intake. Based on these enzyme activities as well as hemoglobin and tissue mineral concentrations, increasing levels of dietary zinc did not affect copper bioavailability. Therefore, supplementation of high levels of zinc in practical diets should not impair the copper status of channel catfish.

Effects of Dietary Lipid Concentration, a Dairy–Yeast Prebiotic, and Fish and Nonfish Protein Sources on Growth, Survival, and Nonspecific Immune Response of Golden Shiners in Indoor Tanks and Outdoor Pools

Abstract We conducted two feeding trials in which golden shiners Notemigonus crysoleucas were given six practical diets: Two basal diets with 5% fish meal and either 4% or 10% supplemental lipid (poultry fat [PF]); two prebiotic diets with 2% dairy–yeast prebiotic, 5% fish meal, and 4% or 10% PF; and two 4% or 10% PF diets that contained no fish meal or prebiotic. To compare diet effects in the presence or absence of natural foods, one trial was conducted in indoor aquaria and one was conducted in outdoor pools. Diet effects were assessed by measuring growth, survival, feed efficiency, and body composition in both trials and Fultons condition factor K in the outdoor pool trial. A subset of fish from the outdoor trial was grown to a larger size for analysis of alternative complement activity (ACH50). The prebiotic enhanced growth and feed conversion ratio (FCR) slightly in the indoor aquarium trial. Weight gain and FCR did not differ among diet groups in the outdoor trial, reflecting the influence of natu...

Evaluation of 36%-Protein Diets with or without Animal Protein for Rearing Tank-Hatched Golden Shiner Fry in Ponds

Abstract The objective of this study was to determine whether fry of golden shiners Notemigonus crysoleucas reared in ponds differed with respect to growth, survival, feed conversion, total yield, condition, and response to low dissolved oxygen when fed a practical diet of 36% protein from animal and plant sources (five ponds) versus a diet of only plant sources (six ponds). Newly hatched fry (1 mg) were stocked at 2.5 × 106/ha in 12 fertilized ponds (0.04 ha each). Fish were fed twice daily at a rate of 8.0–15.9 kg/ha for 12 weeks. Chlorophyll a was not different between diets, indicating that natural food production in ponds was similar between treatments. Between-treatment differences in average individual weight (0.56–0.59 g), relative weight (114.4– 115.6), Fultons condition index (K = 0.88), total yield (40.8–45.6 kg), feed conversion (0.85– 0.95), and survival (75.9–79.2%) were not significant. Postharvest survival of fish exposed to low dissolved oxygen at 20°C in a laboratory test was not affect...

Evaluation of a Dietary Dairy―Yeast Prebiotic in Juvenile Golden Shiners in Ponds

Abstract We evaluated the performance in ponds of juvenile golden shiners Notemigonus crysoleucas fed a control diet or a diet with 2% dairy–yeast prebiotic. Fish weighing 0.1 ± 0.001 g (mean ± SD) were initially stocked into five 0.04-ha earthen ponds per diet at 21.9 kg/ha and fed extruded 35%-protein pellets to satiation twice daily. Subsamples of fish were weighed at 2-week intervals for 6 weeks; the fish were harvested at 7 weeks to avoid reproduction. For golden shiners fed the control and prebiotic diets, the mean individual weight gain (2.93 and 2.89 g, respectively), net yield (214.0 and 198.8 kg/ha), feed conversion ratio (1.34 and 1.47), and survival (61.5% and 64.2%) did not differ. Condition index (Fultons K) was higher in fish fed the control (1.15) rather than the prebiotic diet (1.08). After harvest, 100 fish per pond were acclimated to tanks before being subjected to a bacterial challenge with Flavobacterium columnare. Each pond replicate received one of three experimental treatments: co...

Effect of Temperature on Growth, Feed Utilization, and Immune Status of Channel Catfish in a Recirculating System

Abstract A feeding trial was conducted to determine growth, survival, feed utilization, nonspecific immune response, and proximate and fatty acid composition of the fillet of stocker-sized channel catfish Ictalurus punctatus reared at temperatures considered slightly below optimal (22°C), optimal (27°C), or slightly above optimal (32°C) for feed intake and growth of this species. Groups of 100 stockers initially averaging 111.4 ± 1.7 g (mean ± SE) were stocked into each of four 1,140-L tanks within each of three independent recirculating systems and were fed a 32% protein commercial floating pellet once daily to satiation for 14 weeks. Feed intake was calculated weekly. Subsamples of fish were weighed every 3 weeks to track growth. At the end of the trial, all fish were counted and weighed. Five fish per tank were bled to analyze hematology and immunological parameters. Analysis of variance and Fishers least-significant-difference tests were used to compare differences among treatment means (P ≤ 0.05). W...

A dietary dairy/yeast prebiotic and flaxseed oil enhance growth, hematological and immunological parameters in channel catfish at a suboptimal temperature (15°C).

Channel catfish raised in the southern United States require two growing seasons to reach market size. Growing seasons are separated by a cool period of about 3 months when feed intake and growth are greatly reduced. A cool-weather feeding strategy to improve feed intake, growth or health of catfish might improve survival and reduce the time needed to achieve market size. We conducted a feeding trial with channel catfish at a suboptimal temperature (15°C) to determine the effects of supplementing diets with either a dairy/yeast prebiotic or flaxseed oil (high in 18:3n-3) compared with a control with soybean oil (high in 18:2n-6). The trial was conducted in recirculating systems with 1140-l tanks containing 100 fish each (mean initial weight 61.4 g±0.43 s.e.m.). A 28%-protein basal diet was supplemented with 20 g/kg cellulose and 20 g/kg soybean oil (SBO, control), 20 g/kg cellulose and 20 g/kg flaxseed oil (FLAX) or 20 g/kg of a dairy/yeast prebiotic and 20 g/kg soybean oil (PREB). Fish were fed once daily to satiation and weighed every 3 weeks to track growth. Hematology, non-specific immune responses, proximate and fatty acid composition of muscle were determined to assess diet effects. Catfish-fed FLAX or PREB had higher weight gain, feed consumption and lysozyme activity than fish fed SBO. Total n-3 fatty acids in muscle were higher in fish fed SBO or FLAX than those fed PREB. Total n-6 long-chain polyunsaturated acids were higher in muscle of fish fed PREB than those fed SBO. Fatty acids in the PREB and SBO diets were similar, so the PREB appeared to increase elongation and desaturation of n-6 fatty acids in muscle. Flaxseed oil and the dairy/yeast prebiotic both have potential to increase catfish performance at a low temperature.

Effects of dietary sweet potato leaf meal on the growth, non‐specific immune responses, total phenols and antioxidant capacity in channel catfish (Ictalurus punctatus)

BACKGROUND Traditional energy sources in catfish diets have become costly, and economical alternatives are needed. Sweet potato leaves are underutilised agricultural by-products that provide energy and substantial amounts of phenols, which affect animal and human health. There is little information on the effects of these compounds on catfish, or the capacity of catfish to accumulate dietary phenols. Catfish enriched with phenols have marketing potential as functional foods. This study investigated the effects of diets with sweet potato leaf meal (SPLM) on growth performance, health and total phenolic compounds in catfish. RESULTS SPLM was substituted for wheat middlings in three diets fed to groups of juvenile catfish for 10 weeks. Weight gain, feed conversion, survival, alternative complement activity and lysozyme activity were similar among diets. Haematocrit was lower in fish fed diets with SPLM, but within the normal range. Total phenols and antioxidant capacity in the whole body were similar among treatments. CONCLUSION SPLM was an effective energy source for catfish up to the maximum level tested (230 g kg(-1) diet). SPLM did not enhance total phenols in catfish, but there were no apparent antinutritional effects of the meal on catfish growth, health or survival.

Stable Car bon Iso tope Ratios and Stan dard Pro duction Data as Indices of Golden Shiner, Notemigonus crysoleucas, Per for mance in Pond Feed ing Trials

Abstract This study shows the ef fect of production variables on assimilation of foods by golden shin ers, Notemigonus crysoleucas, in ponds was ex am ined in con cur rent 8-week feed ing tri als at the Uni versity of Ar kan sas at Pine Bluff (UAPB) and Texas A&M Uni ver sity (TAMU). Ten 0.04-ha ponds per site were fer til ized with defatted rice bran and stocked with golden shin ers (ini tial weight = 1.3 g) at a rate of 750,000/ha (UAPB) or 375,000/ha (TAMU). Fish in five ponds per site were fed a nu tri tion ally com plete pre pared diet at 4% of body weight, while fish in the re main ing ponds were not fed. As sim i la tion of nat u ral foods by “unfed” fish was com pared to that of fish fed the pre pared diet at each site. Stan dard pro duc tion data (weight gain, Secchi depth, dissolved ox y gen [DO]) were com pared to sta ble car bon iso tope ra tio (d1 3 C) data as an in dex of fish per for mance (weight change or fish d13 C, re sult ing from as sim i la tion of var i ous food sources). Fish weight change and fish iso tope ra tio were re gressed sep a rately against in de pend ent vari ables (feed amount, Secchi depth, DO, fed/unfed dummy vari able, and study site dummy vari able) to de ter mine their re la tion ships. Nat u ral pro duc tiv ity was con sis tently lower at TAMU than at UAPB, while temper a ture and min i mum DO were sim i lar be tween sites. Weight gains of fed and unfed fish at TAMU were higher than those of fed and unfed fish at UAPB. The d13 C of fed and unfed fish at UAPB changed lit tle dur ing the study and did not al low dis crim i na tion among their food sources. The d13 C of fed fish at TAMU ap proached that of the pre pared diet, while that of unfed fish re sem bled that of the plank ton and rice bran. Pre pared diet quan tity and the study site sig nif i cantly (P > 0.1) af fected fish weight change, but Secchi depth and min i mum DO did not. Weight gain increased with in creas ing diet in put up to a max i mum value, then de clined with ad di tional in puts. Min i mum DO, plank ton iso tope ra tio, and the fed/unfed and site vari ables sig nif i cantly af fected fish iso tope ra tio.