Location: Warmwater Aquaculture Research Unit
2020 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
Pond studies were conducted to evaluate various diets for channel or hybrid catfish. In these studies, fish were fed once daily to apparent satiation for a growing season. Three 24% protein diets containing decreasing levels of soybean meal (30, 20, and 15%) and increasing levels of cottonseed meal and corn germ meal were compared with a 28% protein control diet. There were no significant differences in total diet fed, net yield, weight gain, feed conversion ratio (FCR), survival, or fillet proximate nutrient composition among dietary treatments. Compared with fish fed the 28% protein control diet, fish fed 24% protein diets had lower carcass and fillet yield. Results demonstrated a 24% protein alternative diet containing 20% soybean meal may be substituted for 28% protein diets for hybrid catfish during food fish production.
A traditional all-plant 28% protein control diet was compared to alternative diets with and without lysine and methionine supplementation. Lysine and methionine were added to the alternative diets equivalent to a 32% protein diet to determine the benefit of elevated protein levels related to each supplement. There were no significant differences in total diet fed, net yield, weight gain, and survival among dietary treatments. There were also no significant differences in carcass yield, fillet yield, and fillet proximate composition. Fish fed the alternative diets had slightly, but significantly, higher FCR than fish fed the traditional control diet, which is likely related to higher dietary fiber levels in the alternative diets. Results show there is no benefit to fortification of lysine and methionine in alternative diets on processing yield of pond-raised channel catfish.
Various combinations of alternative protein feedstuffs were used including cottonseed meal, corn distillers dried grains with solubles (DDGS), corn germ meal, peanut meal, and porcine meat and bone meal (PMB) to replace soybean meal in catfish diets. There were no significant differences in total diet fed, net yield, weight gain, survival, processing yield, and fillet proximate composition among dietary treatments. Results show all soybean meal could be replaced by two or three moderate- and high-protein alternative feedstuffs without significantly affecting growth performance, processing yield, and fillet proximate composition of pond-raised catfish during food fish grow out.
Other experiments showed dietary protein levels can be reduced from 35% to 32% and fish meal can be replaced by PMB or pork meat, bone, and blood meal without affecting growth, gross yield, FCR, or survival for pond-raised channel or hybrid catfish fingerlings fed once a day to satiation. Once the fingerlings reach 2½ inches, they could be fed a 32% protein PMB diet.
Fish were either not fed, fed once weekly to satiation for two months to simulate a long-term harvest delay, or fed daily to satiation. After two months fish in half the ponds in each of the feed restricted treatments were harvested and those in the remaining ponds were fed daily for an additional month. Fish not fed for two months lost 14.3% weight, compared with a weight gain of 6.7% for fish fed once weekly. Fish not fed or fed once weekly for two months had reduced visceral fat and fillet yield compared with fish fed daily. At the end of three months, there were no significant differences in weight gain, net yield, fillet yield, or visceral fat whether fish were previously not fed or fed once weekly for two months. Results demonstrate feeding once weekly can generally maintain body weight of hybrid catfish.
Production variables between hybrid catfish nursery ponds fed immediately after stocking (industry standard) versus delayed feeding after stocking were compared. At 2 week (wk) post-stocking, fish in the delayed feeding treatment were significantly smaller than fish in the standard feeding protocol. Therefore, all ponds began receiving commercial diets after 2 wk. At 2 wk post-stocking and continuing through 5 wk post-stocking, average individual fish length and weight was greater in the standard feeding protocol compared to the delayed feeding protocol. At harvest, there were no differences in production variables between the two feeding protocols. Unlike a previous study with channel catfish fry, where feed was withheld for 6 wk without compromising production, noticeable deficiencies in hybrid fry growth were observed after only 2 wks of feed restriction. However, compensatory growth was observed, and restricting feed did not result in differences in production variables observed 6 wk post-stocking. At the feeding rate and prices during this study, delaying feeding for 2 wks saved $15.5/acre in feed costs.
In contrast to channel catfish, hybrid catfish appear to be more aggressive feeders, and fry typically begin consuming a pelleted floating around 2 wk post-stocking. At the time of this study, cost of the 35% protein fry/fingerling dust and mini-pellets used for the study was $0.28/lb. Feed savings by restricting feed during the first 2 weeks came to $1.55/pond or $15.5/acre. However, hybrid fry showed reduced growth after only 2 weeks of restricted feeding. Hybrid fry producers were advised to begin offering commercial diets no later than 2 wk post-stocking, to take advantage of the aggressive feeding behavior of these fish and maximize growth.
To improve feeding methods for channel and hybrid catfish in nursery ponds, stable C and N isotope ratios were used to quantify the fractional contribution of zooplankton and a commercial feed to fish growth. Channel and hybrid catfish fry had no differences in the timing and extent of zooplankton and feed use in ponds. Both fish types used zooplankton and feed equally to support growth (~50% from each source) from the time of pond stocking, and there were no differences in growth rates by length or weight. The fish used feed to support growth before they were visually observed accepting the feed at the surface of ponds 4 weeks after stocking. Zooplankton are clearly important to support desirable growth of channel and hybrid catfish fry in ponds. Thus, managers should monitor densities of preferred zooplankton prey in ponds and use inorganic fertilization methods to enhance zooplankton production, as necessary. Although feed partially supported zooplankton production in this study, managers should not overfeed because this practice is expensive, inefficient, and risks hypoxia formation in ponds. Finding no differences in diets and growth rates between channel and hybrid catfish, we provisionally recommend managers practice similar pond management strategies for both fish types.
The objective to evaluate co-culture of alternative species was removed from the project plan due to dynamic changes in industry production practices and subsequent research priorities. New research focused on adoption and economics of alternative production practices.
U.S. catfish farmers have been exploring alternate production technologies (intensive aeration, in-pond raceways, and split-pond systems) for several years. A multi-state (AR, AL, MS) survey identified split pond as the most rapidly adopted technology, with 1,600 acres in 2013, followed by intensively aerated ponds (1,200 acres) due to high yields and greater control over the production process. High investment costs and increased risk associated with these technologies were the main barriers to adoption. Technology adopters had significantly larger farms, greater numbers of ponds, and a significantly greater percentage used hybrid catfish. Critical factors that influenced aquaculture technology adoption decisions included: (1) method of information transfer, (2) characteristics of the technology, (3) farm characteristics, (4) economic factors, and (5) sociodemographic and institutional factors.
Successful industry-wide adoption of newly developing technologies like split-pond systems and intensively aerated ponds were possible as they brought cost efficiencies. Two economic studies showed that these alternative production technologies were able to spread the higher fixed costs over greater volumes of production. Estimates of cost of production of hybrid catfish raised in split-ponds and intensively aerated systems showed long-term profitability. The cost of catfish production in these systems were sensitive to yield, fish prices, and feed prices and their variations contributed the most to downside risk. A fifth study provided an economic comparison of cost efficiencies in alternative technologies such as split-pond systems, intensively aerated ponds, and in-pond raceway systems under a uniform set of economic assumptions using a standard enterprise budget analysis. Cost of production of hybrid catfish raised in these systems was the highest in in-pond raceways and the lowest from split-ponds. Risk analysis showed stochastic dominance of intensively aerated ponds and split-pond systems over in-pond raceway systems.
A 6-year mixed-integer-recursive programming model was developed to include traditional ponds, re-working existing ponds to make them more productive, converting traditional ponds to split-ponds or adding additional aeration. The model selected primarily adoption of split-ponds as the profit-maximizing strategy under favorable market conditions and unlimited availability of investment capital. Higher feed prices and lower fish prices shifted the profit-maximization strategies from split-ponds to intensively aerated systems and traditional single-batch systems. Restricted availability of investment capital had a strong negative effect on those farms with greater percentages of older ponds that required re-working. Farmers with recently reworked ponds invested the greater profits from the higher yields to transition more rapidly to new technologies. Larger farms could transition greater proportions of the farm to new technologies than could smaller farms.
Accomplishments
1. Reducing feed costs using alternative feed ingredients for catfish food fish production. Soybean meal has been the main protein source for pond-raised catfish because of its high-quality protein and balanced essential amino acid profile. However, soybean meal prices have increased dramatically in recent years and have reached $500/ton at times. Previous research with channel and hybrid catfish has generally shown up to 50% soybean meal could be replaced by cottonseed meal and one of the corn-milling by-products corn gluten feed or corn germ meal, in the diet without negatively affecting fish performance. ARS researchers in Stoneville, Mississippi, and at Mississippi State University in Stoneville, Mississippi, examined using combinations of two or three alternative protein sources to replace soybean meal in 28% protein diets for channel or hybrid catfish. Results demonstrated it is possible to replace all soybean meal by two or three moderate- and high-protein alternative feedstuffs in the diet without significantly affecting growth performance, processing yield, and fillet proximate composition of both channel and hybrid catfish. These data provide flexibility in formulating cost-effective diets for pond-raised catfish. These alternative diets may be used to feed pond-raised catfish during food fish grow out especially during periods of high soybean meal prices.
2. Reducing feed cost for catfish fingerling production. Prices of commercial 35% protein fingerling feeds can sometimes reach $600-700/ton, so catfish fingerling producers desire reduced feed cost. Feed cost can be reduced by lowering protein levels, using less expensive alternative feed ingredients, or both. ARS researchers in Stoneville, Mississippi, conducted three feeding studies to evaluate diets containing 35, 32, or 28% protein with fish meal or pork meat, bone, and blood meal (PMBB), or pork meat and bone meal (PMB) for pond-raised channel or hybrid catfish fingerlings. Results show dietary protein levels can be reduced from 35 to 32% without affecting fish growth performance. Although fish meal is a high-quality protein source for catfish, it does not appear to be a “must have” dietary ingredient for fingerlings raised in properly fertilized nursery ponds and removing it from the diet will substantially reduce feed cost in fingerling production.
3. Channel and hybrid catfish fry had no differences in the timing and extent of zooplankton and feed use in ponds. Both fish types used zooplankton and feed equally to support growth (~50% from each source) from the time of pond stocking, and there were no differences in growth rates by length or weight. ARS reserachers in Stoneville, Mississippi, discovered that the fish used feed to support growth before they were visually observed accepting feed at the pond surface 4 weeks after stocking. Zooplankton are clearly important to support desirable growth of channel and hybrid catfish fry in ponds. Thus, managers should monitor densities of preferred zooplankton prey in ponds and use inorganic fertilization methods to enhance zooplankton production, as necessary. Although feed partially supported zooplankton production in this study, managers should not overfeed because this practice is expensive, inefficient, and risks hypoxia formation in ponds. While the current experiments showed no differences in diets and growth rates between channel and hybrid catfish, managers should practice similar pond management strategies for both fish types.
4. Developing cost-effective feeding strategies to maintain body weight of market-size hybrid catfish during harvest delays. Several circumstances, such as off-flavor, oversupply of fish in the market, or low fish prices, can cause delays in harvesting market-size fish in catfish production. Delays in harvest increases the risk of fish losses and restricts cash flow resulting in diminished production efficiency. Harvest delays can become a serious issue, especially for hybrid catfish, since they feed more aggressively and grow faster than channel catfish. ARS researchers in Stoneville, Mississippi, conducted a pond study examined effects of no feeding, maintenance feeding (feeding once weekly) and refeeding on production and processing characteristics, and fillet proximate composition of market-size hybrid catfish. Results show feeding once weekly can generally maintain fish body weight, and no feeding or feeding once weekly for two months does not affect survival but significantly reduces fillet yield. These data provide catfish producers with information that can be used to minimize production losses in events of long-term harvest delays.
