Application of Nutritional Strategies for the....
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GRANT NUMBER: NA77FD0070         NMFS NUMBER: 96-SER-029

REPORT TITLE:  Application of Nutritional Strategies for the Development of Low-Pollution Feeds for Marine Species

AUTHOR:  C. R. Arnold and D. Allen Davis

PUBLISH DATE: January 19, 1999

AVAILABLE FROM:  National Marine Fisheries Service, Southeast Region, 9721 Executive Center Drive, St Petersburg, Florida 33702.   TELEPHONE:  (813) 570-5324


This research was designed to advance environmentally sound aquaculture through the development and demonstration of low-pollution feeds for the commercial production of red drum, Sciaenops ocellatus and the Pacific white shrimp, Penaeus vannamei.   A portion of this research evaluated the use of a feed grade protease (FGP) as a potential dietary supplement to enhance protein retention in juvenile shrimp and fish offered high quality practical diets. The supplementation of 0.1 to 0.4 g FGP/100g diet did not result in increases in weight gain or feed efficiency for either species. Based on these results, as well as other published studies, it would appear that enzyme treatments of feeds and/or feed stuffs will be most beneficial in poorly digested feeds and/or feed stuffs or in situations in which there is no endogenous enzyme source. However in diets designed to contain high digestible nutrients, such as those used reduce pollution loading, enhancement of nutrient availability appears minimal. The second component of this research initiated nutrition studies for the development of growout diets for red drum and also evaluated the potential of phase feeding strategies. These studies represent the first attempts to evaluate nutritional requirements of large red drum under controlled conditions. The first growth trial evaluated six practical diet formulations that were offered to red drum (initial mean weight 50 g) over a 13-week growth trial. Results indicate that reducing the protein content of the feed from 44 to 32% will significantly reduce growth and feed efficiency values. Increasing the lipid content, and subsequently the E:P ratio, of the 44% protein diet from 6.8 to 13.2% did result in some positive increases in performance (e.g. increased FE as well as slight increases in protein conversion efficiency and final weight). However, the negative aspects of increased lipid deposition as demonstrated by significant increases in intraperitoneal fat deposition may outweigh any increases in performance. Additionally, reducing the E:P ration of the 32% protein diet by replacing wheat starch with indigestible filler, did not result in a significant increase in consumption or final weights of the fish. This response would indicate that the carbohydrate component of low protein diets is probably not being digested and hence is adding to the organic loading of a culture systems. Another method to reduce production cost and nutrient loading in growout systems would be to utilize phase feeding strategies that would employ reduced level of protein as the fish grows. To evaluate this feeding strategy three practical diets were formulated to contain 44, 40 and 36% protein. Red drum (mean initial weight 70.8g) were either feed these diets throughout a 17-week growth trial or offered the 44% protein diet for the first 8-weeks and then the 40 or 36% protein diets for the remainder of the growth trial. Although, the differences in final weights were not significant, there was a general decrease (592.8 vs 543.3g) in weights of the fish as the protein content of the diet was reduced from 44 to 36% respectively. A similar response was also seen in the phase feeding treatments. Similarly, significant reductions in FE values were observed as protein content of the diet was reduced. Given the minimal differences in the final weights of the fish, reducing the protein content of growout diets appears to be a potentially viable option. However, when considering this each producer must consider his situation. Particular consideration must be given to reductions in FE, since this will result in increased cost associated with shipping, feed milling and storage. Additionally, as demonstrated in previous research reductions in the nutrient density of the diet will also result in increased organic loading of the culture system, which may lead to increased costs for pollution abatement. These results, will facilitate improvements in both growout diets and feeding strategies for the commercial production of marine species.

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