Location: Warmwater Aquaculture Research Unit2013 Annual Report
1a. Objectives (from AD-416):
1) Identify mechanisms and develop tools and methods to improve growth efficiency of catfish. 2) Determine mechanisms of host-pathogen interactions and sources of variation in catfish immune function to improve catfish health and survival. 3) Improve efficiency of channel and blue catfish reproduction and channel x blue hybrid production. 4) Identify genomic regions affecting variation in traits of economic importance through quantitative trait locus (QTL) discovery and fine mapping strategies. 5) Develop, and transfer to commercial producers, channel catfish and blue catfish germplasm improved for growth, yield, and disease resistance for improved production of channel, blue and hybrid catfish.
1b. Approach (from AD-416):
To attain the first objective, we will correlate mitochondrial functional variation with catfish feed efficiency and identify and determine the role of specific genes and gene products (peptides and proteins) involved in controlling growth in catfish. For the second objective, we will construct a catfish microarray targeted toward immune function, characterize functional genetic variation in resistant vs. susceptible channel catfish, and characterize the effect of prebiotic administration on catfish immune function. For the third objective we will induce early maturation in channel catfish and blue catfish through compressed annual temperature cycles, increase ovulation and fertilization efficiency for production of blue X channel F1 hybrid catfish, and establish a technique for spematogonial transplantation between blue and channel catfish. For the fourth objective we will enhance and integrate genetic and physical maps, and identify quantitative trait loci associated with superior production traits, especially carcass traits and survivability to E. ictaluri infection. For the fifth objective, we will produce a line of select channel catfish based on multi-trait selection within a commercial composite population, produce a line of select blue catfish based on males that produce hybrid offspring with superior growth and carcass yield, and produce male channel and blue catfish which have a YY sex chromosome complement for all male catfish production.
3. Progress Report:
Higher demand, consistent superior performance and increased availability of blue x channel hybrid catfish fry have contributed to increase hybrid catfish production. Hybrid catfish are expected to comprise 35% of the total catfish processed. Commercial hatcheries are expected to produce 180 million hybrid catfish fry in 2013, an increase of 30 million fish from the previous year, due in part to improved hybrid production technologies developed and transferred to industry by ARS scientists at the Warmwater Aquaculture Research Unit, in Stoneville, MS. Unit research continues to address improvements in hybrid production efficiency. Breeding experiments demonstrated that when channel catfish broodstock were selected based on their predicted genetic value, their offspring grew faster than offspring of non-selected broodstock. Therefore pedigree-based individual selection, rather than family-based selection, continues within the Delta Select catfish line to improve efficient growth and carcass traits. Breeding experiments have also shown that production of superior hybrid catfish does not depend on matings of specific individual blue and channel catfish broodstock; thus, selection for improved hybrid catfish may be based on selection within each parent species. Catfish that were fed diets containing essential oils were more resistant to bacterial pathogens than catfish fed control diets. Based on this information, several catfish producers have incorporated essential oils into their catfish diets and report improved production.
1. Evaluation of channel x blue and purebred channel catfish performance from 4 commercial farms. Channel x blue hybrid catfish production and use by the catfish industry have increased substantially in the last 3 to 5 years. ARS scientists with the Warmwater Aquaculture Research Unit in Stoneville, MS, established non-funded cooperative agreements with the 4 largest producers of hybrid catfish in the United States to determine the effects of channel catfish strain, and female within strain, on hybrid offspring growth and carcass yield. In addition, purebred catfish from the same females will be evaluated for growth and carcass yield. This project was developed at the request of the producers and will provide information to determine if certain strains produce superior hybrid offspring, how much of differences in offspring performance are due to differences individual female parent, and if purebred channel offspring performance is predictive of hybrid offspring performance. All of this information will be important to producers as they develop breeding plans to improve hybrid catfish performance.
2. Estimation of genetic parameters for growth, enteric septicemai of catfish (ESC) resistance and carcass composition in channel catfish. Estimates of heritabilities, the proportion of phenotypic differences due to genetic variation, for economically important traits are required for efficient selective breeding to improve these traits in channel catfish. ARS scientists with the Warmwater Aquaculture Research Unit in Stoneville, MS, continue to collect data and improve accuracy of breeding value estimates of for growth, fillet yield and body composition of channel catfish as part of our breeding program. Selected fish have shown improved growth compared to unselected controls. Selected fish have not yet been evaluated for fillet yield. This research is part of a breeding program to improve important traits in channel catfish for ultimate release of improved germplasm to the industry.
3. Production and evaluation of hybrid catfish from various strains of blue catfish. Commercial culture of channel catfish x blue catfish hybrids continues to increase, but little is known concerning the genetic contributions from the blue catfish. ARS scientists with the Warmwater Aquaculture Research Unit in Stoneville, MS, conducted two studies in which blue male catfish were mated to female channel catfish using a factorial mating design to estimate additive and dominance genetic effects for growth and carcass yield of hybrid catfish offspring. In the first study, blue male catfish from a single strain were mated to multiple channel catfish females and hybrid offspring were measured for growth and carcass yield. Progeny were reared in communal ponds and parentage was determined by inheritance of DNA markers. In the second experiment a similar experimental design was used, but 10 males from each of 5 blue catfish strains were used in matings. Results of both studies demonstrated a significant maternal effect on growth and carcass yield, substantial additive genetic effects of blue catfish sires on growth and carcass yield of hybrid offspring, and minimal dominance genetic effects on performance of hybrid progeny. This information is critical to efficient selection of purebred blue and channel catfish parents to improve performance of hybrid offspring.
4. Effects of male to female ratio and broodfish density on spawning success in pond-spawned channel catfish. Channel catfish are reproduced by placing mature male and female catfish in spawning ponds, the fish mate in spawning containers placed in the ponds and farmers collect egg masses periodically. Improving efficiency of pond spawning would improve profitability of catfish farming. ARS scientists with the Warmwater Aquaculture Research Unit in Stoneville, MS, conducted two studies to determine if spawning success could be improved by altering the ratio of male and female broodstock in the spawning pond. A stocking ratio of 1 male to 1 female brood channel catfish (used by industry) was compared to a ratio of 1 male to 4 females. Both treatments had a stocking density of 1,000 pounds (lbs) per acre. The 1:4 stocking ratio produced fewer spawns and fewer fry per acre than the 1:1 ratio so farmers would not benefit from decreasing the male to female ratio to 1 to 4. In another study, broodstock were stocked at a male to female ratio of 1:2 at stocking densities of 1,000 lbs per acre (a rate used by industry) and 2,000 lbs per acre. Broodfish stocked at 2,000 lbs per acre produced approximately twice as many spawns and fry per acre. Therefore farmers could benefit by stocking broodfish ponds at higher stocking densities than commonly used.
5. Evaluation of processing yield in fish from nutrition studies. Diet composition can affect fillet yield and composition, traits that influence profit and product quality. ARS scientists with the Warmwater Aquaculture Research Unit in Stoneville, MS, in cooperation with researchers from Mississippi State University and the University of Arkansas-Pine Bluff (a 1890s institution), processed catfish from multiple studies to provide carcass quality measurements for a variety of experiments. The carcass data will help researchers determine the impact of altering diet composition on processing yield in order to identify diets that will improve production efficiency.
6. Regulators of feed efficiency in catfish. Producers desire improved feed conversion efficiency to lower costs of production, but the regulation of feed efficiency is not well understood in catfish. Therefore, ARS scientists with the Warmwater Aquaculture Research Unit in Stoneville, MS, in cooperation with researchers from West Virginia State University, investigated messenger ribonucleic acid (RNA) levels and enzyme activities of genes involved in the mitochondrial respiratory chain in catfish families that demonstrated low or high feed efficiency. Mitochondrial enzymatic complex activities in the liver were reduced in the fish with high feed efficiency compared to catfish with low feed efficiency. Also the enzyme activities in the liver, muscle and intestine were lower in fast growing, low feed efficiency catfish. These data showed that the activities of specific mitochondrial enzymes have the potential to serve as selection markers for improved feed efficiency.
7. Regulators of growth in catfish. Catfish that grow fast and efficiently utilize feed benefit catfish production but factors that regulate growth are not well understood. Therefore, ARS scientists in the Warmwater Aquaculture Research Unit in Stoneville, MS, measured levels of gene activity and levels of gene products that regulate growth and efficiency. Plasma levels of insulin-like growth factor 1 were higher in faster growing compared to slower growing fish, and levels of insulin-like growth factor 2 messenger ribonucleic acid (RNA) in muscle and liver were higher in fast growing fish. Messenger RNA levels of ‘cocaine and amphetamine-regulated transcript’ (CART), a gene implicated in feeding behavior, were higher in faster growing fish. Whole body fat was higher in faster growing fish, and protein retention and feed conversion efficiency were similar between fast and slow growing fish. Results suggest that IGF-I and IGF-II play important roles in faster growing fish. In addition, faster growing fish consume more food which may be triggered by CART activity and deposit more fat. Protein retention and feed efficiency were similar in fast and slow growing fish. Understanding the genes and gene products involved in faster growing fish as well as how energy is utilized and deposited should be considered when making selections for improved growth performance in channel catfish.
8. Evaluation of essential oils for improving catfish immunity. Losses to disease significantly impact catfish production so practical approaches are needed to improve catfish immunity. Research conducted by ARS scientists at the Warmwater Aquaculture Research Unit in Stoneville, MS, showed fish fed essential oils have a 40% improvement in resistance to the bacterial pathogen Edwardsiella ictaluri. After 1 day of feeding, plasma levels of mannose binding lectin were three-fold higher in fish fed essential oils but lowered to control levels 7 days after feeding. In contrast, activities of the interleukin 6 gene, a mannose binding lectin gene, and a rhamnose binding lectin gene were significantly increased in the liver of treated fish after 14 days of feeding. The experiments provided evidence that essential oils increased survivability by stimulating production of the lectin proteins that bind to carbohydrates on the bacterial surface.
9. Extending spawning readiness of channel catfish by exposing vitellogenic channel catfish females to lower temperatures. Environmental temperature controls the seasonal maturation of gonads and spawning of channel catfish, and temperature fluctuations during the spawning season can adversely affect broodfish condition and egg availability. Therefore, temperature fluctuations can reduce the number of gravid females that are available during the later stages of the spawning season which limits the production of hybrid catfish fry. ARS scientists at the Warmwater Aquaculture Research Unit in Stoneville, MS, exposed vitellogenic channel catfish broodstock to cooler temperatures to extend their spawning readiness towards the end of the spawning season. Exposure of broodstock to temperatures 3-5°C cooler than pond temperature for 10 days during the post-vitellogenic period provided available eggs from 25% of the treated broodstock toward the later part of the spawning season. This technique can be used to facilitate the availability of more eggs to hatchery producers to meet their production goals.
10. Comparison of hatching survival and progeny performance in catfish spawned naturally or artificially. Commercial production of channel catfish fry depends primarily on anonymous, random mating of parental fish in ponds. Prior research has shown that a small proportion of males may participate in pond mating which can lead to undesired levels of inbreeding. ARS scientists at the Warmwater Aquaculture Research Unit in Stoneville, MS, compared reproductive and growth traits of 6 families of pond-spawned channel catfish, and 6 families each of maternal half-sibling artificially spawned purebred and hybrid catfish. Growth, survival, feed conversion and stress levels of hybrid catfish did not differ from artificially spawned channel catfish either in controlled or pond conditions. Half-sibling hybrid and channel catfish families were also more resistant to enteric septicemia of catfish (ESC) disease challenge compared to naturally spawned channel catfish. These experiments suggest that while artificial spawning provides greater control of genetic variation and pedigree, it may not inhibit performance of progeny compared with natural spawning.
11. Efficacy of salmon and chicken gonadotropin-relesing hormone (GnRH) analogs to induce maturation and ovulation in channel catfish females to produce hybrid catfish. Demand for hybrid catfish fingerlings is rapidly increasing but hybrid fry production is difficult due to natural reproductive barriers between the two parental species. To overcome this constraint, synchronous ovulation is induced in female channel catfish using exogenously administered hormones. The two most thoroughly investigated hormones are carp pituitary extract (CPE) and a synthetic analog of mammalian gonadotropin releasing hormone (mGnRH, also called luteinizing hormone-releasing hormone or LHRHa). Hormone spawning is expensive and labor-intensive, and ARS scientists at the Warmwater Aquaculture Research Unit, Stoneville, MS, are investigating alternative hormones that may be easier to use, more effective, or less expensive. In one study, ARS scientists at the Warmwater Aquaculture Research Unit established a non-funded cooperative agreement with Western Chemicals, Inc., to evaluate the efficacy of salmon gonadotropin releasing hormone analog (sGnRHa) to ovulate female channel catfish. The minimum effective dose was determined to be 10 µg OvaRH/kg body weight, which was tested in three commercial hatcheries. Results prompted the manufacturer to sponsor the peptide for Investigational New Animal Drug (INAD) exemption in 2012. Results at ARS and commercial catfish hatcheries showed the recommended dose of the peptide reduced the cost of hormone by 50% and reduces the cost of producing hybrid embryos at the hatching facility. In another study ARS scientists at the Warmwater Aquaculture Research Unit, compared the effectiveness of a synthetic hormone based on the structure of chicken GnRHII (cGnRHII), mGnRHa, and sGNRHa. The synthetic cGnRHII increased the number of females ovulated while maintaining fry quality and quantity compared to the mammalian and salmon hormone analogs.
Chatakondi, N.G., Kelly, A.M. 2013. Ooctye diameter and plasma vitellogenin as predicitve factors to identify potential channel catfish, Ictalurus punctatus suitable for induced spawing. Journal of the World Aquaculture Society. 44(1):115-123.