Location: Warmwater Aquaculture Research Unit
2018 Annual Report
Objectives
1) Evaluate alternative feedstuffs and optimize feed formulations using traditional and alternative feedstuffs for cost-effective production of catfish, and determine if nutrient requirements differ for hybrid and channel catfish.
Sub-objective 1.1 Evaluate diets using alternative feedstuffs in low-protein diets for pond-raised hybrid catfish.
Sub-objective 1.2 Evaluate fortification of alternative diets with lysine and methionine to improve processing yield of channel catfish.
Sub-objective 1.3 Complete replacement of soybean meal using a combination of lower-cost protein sources for pond-raised hybrid catfish.
Sub-objective 1.4 Evaluate 32% or 36% protein, traditional or alternative feeds for fingerling hybrid catfish.
Sub-objective 1.5 Evaluation of growth and disease resistance of fish fed diets supplemented with taurine.
2) Develop more cost effective feeding and production strategies for hybrid and catfish production.
Sub-objective 2.1 Evaluate effects of maintenance feeding on growth and processing yield of market-size hybrid catfish.
Sub-objective 2.2 Compare hybrid fry production when feeding immediately at stocking with fry fed under an alternative feeding strategy of waiting six weeks before offering commercial diets.
3) Evaluate co-culture of alternative species for effects on water quality, biological control of disease vectors, and supplemental income for catfish producers.
Sub-objective 3.1 Co-culturing redear sunfish with channel catfish under commercial conditions.
Sub-objective 3.2 Extensive production of prawn Macrobrachium rosenbergii in fallow catfish production ponds for crop diversification.
Approach
Three 24% protein diets containing 30, 20, and 15% soybean meal will be compared with a 28% protein control diet. Hybrid catfish fingerlings will be stocked in ponds at 6,000 fish/acre. Each diet will be fed to five replicate ponds. All ponds will be harvested in October/November. A partial budget analysis based on feed and fish prices will be conducted to determine the economic benefit (if any) of using low-protein alternative diets versus the traditional control diet.
This study will evaluate five 28% protein diets fortified with varoious supplements. Experimental design, diet analyses, procedures for stocking, feeding, pond management, data collection and statistical and economic analysis will be the same as described for Sub-objective 1.A.
All soybean meal in hybrid catfish feeds will be replaced with various combinations of cottonseed meal, distiller’s grains with solubles, peanut meal, and porcine meat and bone meal. Pond will be stocked with hybrid catfish fingerlings, and diet analyses, experimental design, procedures for stocking, feeding, pond management, data collection and statistical analysis, and economic analysis will be the same as described for Sub-objective 1.A.
Four thousand small hybrid catfish fingerlings will be stocked into 20 tanks with 200 fish each. Four diets of 32% or 36% protein using either soybean meal or soybean substitutes will be evaluated. Diet, statistical, and economic analysis will be the same as described for Sub-objective 1A.
Growth and disease resistance of juvenile channel catfish will be evaluated in fish fed diets with varying levels of taurine in replicated aquaria.
The proposed study will evaluate effects of no feeding, maintenance feeding, and re-feeding on growth, feed conversion ratio, and processing yield of hybrid catfish. Market-size hybrid catfish (1.5 lb) will be stocked into ponds at the end of May or early June. The experimental design, procedures for stocking, feeding, pond management, data collection and statistical analysis will be the same as described for Sub-objective 1.A.
This study will compare production of hybrid fry fed immediately at stocking in 0.4 ha ponds with that of fry not fed until 6 weeks after stocking.
Four ponds will be stocked with channel catfish (600 fish/pond) and redear sunfish (10 fish/pond); four ponds will be stocked with redear sunfish only (10 fish/pond); four ponds will be stocked with catfish only (600 fish/pond). The study will be repeated yearly with the same stocking rates but with varying fish size. Catfish will be fed and managed according to standard industry practices and cultured through one production season.
Each treatment will consist of 4 replicate ponds to evaluate using hay, planted wheat, or rice as substrates to increase freshwater prawn production. Ponds with no substrate addition will served as controls. Ponds will be stocked with 10,000 prawn/ac. All ponds will be fed range cubes. Prawns will be harvested in the fall. All prawns will be counted and collectively weighed, and production will be compared among the treatments.
Progress Report
A pond study was conducted to examine the growth performance of pond-raised hybrid catfish (female channel catfish × male blue catfish) fingerlings fed diets containing two levels of protein (35% or 32%) with two animal protein sources (fish meal or porcine meat, bone, and blood meal [PMBB]). Small fingerlings with a mean initial weight of 2.0 grams (g)/fish were stocked into 20 earthen ponds at a density of approximately 172,970 fish/hectare (ha). The fish were fed once daily to apparent satiation for 113 days. Total weight of feed fed, gross yield, feed conversion ratio (FCR), condition factor, and observed mortality were not significantly affected by either dietary protein concentration or animal protein source. Results demonstrate dietary protein levels can be reduced from 35% to 32% without compromising fish growth and FCR for hybrid catfish fingerlings raised from 2 to 71 g in a growing season. Porcine meat, bone, and blood meal may completely replace fish meal in the diet. At current feed prices, a 32% protein diet with PMBB can provide considerable savings compared with the 35% protein diet with fish meal that is now used in commercial hybrid catfish fingerling production.
Two pond experiments were conducted to evaluate responses of hybrid catfish to “super-dosing” of 6-phytase added to existing commercial catfish feeds. In each experiment, two diets with or without a phytase super-dose (2,500 and 5,000 phytase units [FTU]/kg from two manufacturers, respectively) were compared. In Experiment 1, fingerlings (mean weight: 59 g/fish) were stocked into 17 0.4-ha earthen ponds at 17,290 fish/ha, and were fed once daily to apparent satiation for 198 days. In Experiment 2, fingerlings (mean weight: 47 g/fish) were stocked into 10 0.4-ha ponds at 24,710 fish/ha, and were fed for 128 days. In both experiments, there were no significant differences in total feed fed, gross yield, final fish weight, survival, or blood packed cell volume between fish fed diets with or without phytase. The diets also had no significant effects on pond water-column total phosphorus or chlorophyll a concentrations, but soluble reactive phosphorus concentrations were significantly higher in ponds receiving the phytase diet in Experiment 2. Phytase super-dosing of nutritionally complete feeds does not appear to have additional benefits beyond the standard phytase dose on production characteristics or packed cell volume of pond-raised hybrid catfish, and had no beneficial effects on water quality.
In the catfish industry, fry are usually offered commercial diets as soon as they are stocked in ponds. Since zooplankton are a preferred food item, fry probably subsist on natural food items during this time, and the feed added may be unexploited resulting in unnecessary expenses. To reduce feed costs, pond studies were conducted to determine if channel catfish and hybrid catfish could be raised during the fry to fingerling production stage without adding supplemental feed. For channel catfish, delayed feeding for 5 weeks after stocking did not significantly reduce total fish production, saving at least $236/acre (ac).
Production variables of hybrid catfish were compared between fish fed immediately after stocking (standard industry practice) and fish receiving postponed feeding after stocking. Ponds (0.1 ac) were stocked with swim-up fry at 100,000 fish/ac. At 2 weeks post-stocking, fish in the postponed feeding treatment were significantly smaller than fish in the standard feeding protocol. Therefore, all ponds began receiving commercial diets after 2 weeks. At 2 weeks post-stocking and continuing through 5 weeks post-stocking, the average individual fish length and weight was greater for the standard feeding protocol than for the postponed feeding protocol. At harvest, there were no differences in production variables between the two feeding protocols. Unlike the previous study with channel catfish fry, where feed was withheld for 5 weeks without compromising production, noticeable deficiencies in hybrid catfish fry growth were observed after only 2 weeks of feed restriction. However, compensatory growth was observed, and postponed feeding did not result in differences in production variables observed 6 weeks post-stocking. At the feeding rate and feed prices during this study, we observed feed savings of only U.S. $38.75/ha by postponing feeding for 2 weeks.
As part of a collaborative project with the Catfish Fish Health Initiative, we are working with catfish producers in the Delta region of Mississippi to collect environmental data, including real-time water temperature, dissolved oxygen, light penetration, and bloom characteristics to use as covariates in an attempt to model and predict outbreaks of virulent Aeromonas hydrophila (vAh). Phytoplankton communities and water quality variables has been characterized in infected and non-infected populations of fish and data is being used to establish a Bayesian decision model to determine risk factors associated with vAh outbreaks.
The U.S. catfish industry has shown increasing trends towards intensification of production as a means of achieving cost efficiencies on farms. Previous studies depicted the potential for cost efficiencies in alternative technologies such as split-pond systems, intensively aerated ponds and in-pond raceway systems. This study provides an economic comparison of these systems under a uniform set of economic assumptions using standard enterprise budget analysis. Cost of production of hybrid catfish raised in these systems ranged from $2.03 to $2.91/kilogram (kg), the highest cost being that of in-pond raceways and the lowest from split ponds. Positive annual net cash flows from split-pond systems and intensively aerated ponds were sufficient to make the investment profitable. Cumulative effects of high investment cost (high annual fixed costs), poor survival, and lower yields from the in-pond raceway systems made it economically infeasible. However, the feed conversion ratio (FCR) was the best among these technologies. Risk analysis showed stochastic dominance of intensively aerated ponds and split-pond systems over in-pond raceway systems. Variations in catfish price, yield, and FCR were the major contributors to economic risk. Implementing combinations of intensively aerated ponds and split-pond systems should be viewed as a strategy to respond to production and market needs.
A pond experiment was conducted to evaluate the economics of raising channel catfish in intensively aerated ponds. Channel catfish fingerlings (mean weight: 41 g/fish) were stocked at different densities of 15,000, 20000, 25,000 and 30,000/ha with six replicates ponds (0.4ha) per treatment. A pentaplicate treatment of hybrid fingerlings stocked at 30,000/ha were also simultaneously studied to evaluate the relative economic performance of channels in intensive environment in comparison to the most common hybrids stocking strategy (30,000/ha). All the ponds were provided with a fixed paddlewheel aeration rate of 7.46 kilowatt (kW)/ha and were fed once daily to apparent satiation for 206 days. Among the channels, the gross yield ranged from 7,457 to 10,272 kg/ha showing linear trends related to the initial stocked biomass. However, the cost of production did not show such linear trends and was highest ($2.64/kg) in the lowest density treatment (15,000/ha) while being least ($2.18/kg) in the 20,000/ha treatment. Relative to the channel catfish treatments, the hybrid treatment (30,000/ha) out performed channels in terms of yield and growth rate, resulting in lowest cost of production ($1.90/kg). This study showed that the channels do not perform well over densities of 20,000/ha and farms who have yield maximizing objective should achieve so through raising hybrids instead of channels in intensively aerated settings.
Accomplishments
1. Reducing feed cost for catfish fingerling production. Prices of commercial 35% protein fingerling feeds can sometimes reach $600-700 per ton, so there has been interest among catfish fingerling producers in reducing feed cost. Feed cost can be reduced by lowering protein levels, using less expensive alternative feed ingredients, or both. A feeding trial was conducted to evaluate diets containing 35% or 32% protein with fish meal or pork meat, bone, and blood meal (PMBB) for pond-raised hybrid catfish fingerlings. The 35% protein diet with fish meal was similar to commercial catfish fingerling feeds in diet composition and was used as the control. Results show no significant differences in total amount of feed fed, gross yield, feed conversion ratio, or observed mortality in fish fed 35% or 32% protein diets containing fish meal or PMBB. Using the 32% protein diet with fish meal, 35% protein diet with PMBB, and 32% protein diet with PMBB could save $20, $69, and $89 per ton less than the control, respectively, which are equivalent to annual savings of $120, $414, $534 per acre, if a total of 6 tons of feed per acre (ac) were fed in a growing season. Although feed prices often fluctuate, there will be some savings using the 32% protein diet with PMBB, because fish meal is much more expensive.
2. Reducing feed cost for catfish fry production. Although catfish fry initially subsist on natural food items, they are typically offered commercial diets as soon as they are stocked. Pond studies were conducted on both channel catfish and hybrid fry to determine if feeding ponds could be delayed without compromising production. Delayed feeding of channel catfish fry for 5 weeks can save $236/ac in feed costs without compromising production. However, hybrid catfish fry production starts to be affected at only 2 weeks of delayed feeding. Delayed feeding of hybrid fry for 2 weeks saves only $15.69/ac.
Review Publications
Li, M.H., Bosworth, B.G., Lucas, P.M. 2018. Evaluation of porcine meat and bone meal in diets for pond-raised hybrid catfish. North American Journal of Aquaculture. 80(1):69-73.
Tucker, C.S., Mischke, C.C., Brown, T.W., Torrans, E.L. 2016. Water quality and plankton communities in hybrid catfish (female channel catfish, Ictalurus punctatus x male blue catfish, I. furcatus) ponds after partial fish harvest. Journal of the World Aquaculture Society. 48:46-56.
