S501: Improving Growth and Feed Efficiency in Warmwater Aquaculture
Statement of Issues and JustificationThe farm-gate value of U.S. aquaculture exceeded $1 billion in 2006, and nearly 70% of the crop value was produced in the southeastern states. Aquaculture is an important part of southeastern agriculture, and its importance reaches far beyond the farm gate. Most of the support functions for the industry, such as feed manufacture and equipment fabrication, also take place in the region. The total economic impact of aquaculture is therefore many times the value of production alone. Although channel catfish farming dominates southern aquaculture, many species are cultured and southern aquaculture is, in fact, very diverse.
Increased energy, feed, and labor costs have reduced the profitability of aquaculture. Since feed accounts for about 50% of variable operating costs in aquaculture, development of cost-effective feeds and optimum feeding strategies will reduce production costs. This cooperative project involving aquaculture nutritionists at the Louisiana State University Agricultural Center and Mississippi State University will address problems in the culture of channel catfish (the most important species in the region) and three emerging species with commercial potential: blue catfish, channel x blue catfish hybrids, and coppernose bluegill.
Phospholipase A2 is an enzyme that promotes the production of prostaglandins and leukotrienes, key mediators of the gut inflammatory response. Blocking the enzyme with anti-phospholipase antibody A2 (aPLA2) inhibits the inflammatory response, and thus may improve nutrient absorption and growth of fish. Feeding aPLA2, a natural compound obtained from chicken eggs, increases growth of rainbow trout by 27% in laboratory trials (Barry et al. 2007). If a similar effect occurs in channel catfish, aPLA2 might become a useful feed additive for catfish.
Although most catfish raised in U.S. are channel catfish, recently there is interest in raising blue catfish and channel x blue catfish hybrids because they are resistant to certain diseases affecting channel catfish (Plumb and Chappell 1978; Wolters and Johnson 1994; Wolters et al. 1996; Bosworth et al. 2003). Although comparative studies on protein requirements of these catfish have been conducted in aquaria (Bosworth et al. 1998; Webster et al. 2000), we are unaware of any such pond studies. Results from previous pond studies comparing channel and blue catfish growth have been inconclusive (Perry and Avault 1970; Tidwell and Mims 1990; Grant and Robinette 1992). A pond study recently completed at Mississippi State University indicates that blue catfish can be successfully raised as an alternative to channel catfish by feeding a 32%-protein diet. However, the optimum protein levels for blue catfish growing from fry to fingerlings remain to be determined.
In addition to being more disease resistant, the catfish hybrids grow and convert feed better than either parent (Dunham et al. 1994; Argue et al. 2003; Li et al. 2004). Inherent reproduction problems have been partially overcome in recent years and there is now limited commercial culture of the hybrids. In 2006, over 25 million of hybrid fingerlings were produced. Several knowledge gaps have been identified by the hybrid growers, including best culture and feeding practices. There is lack of information on optimum stocking densities, production cycle, and feeding frequency for the hybrids. Results will help producers to improve hybrid production efficiency.
The coppernose bluegill is a subspecies of bluegill that occurs naturally in peninsular Florida. It grows faster than the common bluegill (Prentice and Schlechte 2000). The rapid growth of coppernose bluegill has made this fish a popular species for use in recreational ponds. The fish readily accepts pelleted diets which makes it a promising potential candidate for intensive aquaculture in the region, where alternatives to catfish culture could be helpful to producers seeking diversification. Research information on culture practices for coppernose bluegill is lacking. Most of the published reports on sunfish aquaculture deal with common bluegill and other sunfish (Tidwell et al. 1992, 1994; Webster et al., 1992, 1997; Wang et al. 1998a, b; Anderson et al. 2002; Hoagland et al. 2003; Twibell et al. 2003). This project will develop practical methods for the intensive production of coppernose bluegill as a food fish, to provide aquaculturists with a cost-effective alternative to the production of other freshwater species. Production of coppernose bluegill as a new aquacultural food commodity has potential to increase the profitability of fish farming in the region.
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