Submitted to: Book of Abstracts World Aquaculture Society
Publication Type: Abstract Only
Publication Acceptance Date: December 1, 2001
Publication Date: January 27, 2002
Citation: Rawles, S.D., Rutger, J.N., Gatlin, D.M., Bryant, R.J. Mineral availability in low-phytate and other rice products in extruded diets for sunshine bass morone chrysops x m. saxatilis.. Book of Abstracts World Aquaculture Society. 2002. [abstract] p.274. Technical Abstract: The availability of various minerals in rice products to fish can be affected by a number of factors including the variety of rice and post-harvest processing. Rice bran is a rich source of fat (rice oil), several B vitamins, and phosphorus. Raw rice bran has a very short shelf life due to its high fat and inherent lipase content which rapidly degrades the fat once the bran is separated from the kernel during milling. Post-milling stabilization subjects the rice bran to heat and pressure which inactivates lipase without destroying the nutritional value of the bran. Additionally, rice bran produced from mutant, low-phytate rice should theoretically exhibit greater phosphorus as well as other mineral availability when included in sunshine bass diets. Limited information is available regarding the availability of nutrients and minerals in feedstuffs for sunshine bass, Morone chrysops X M. saxatilis. This information is needed to allow appropriate substitution of feedstuffs in least-cost formulations and to avoid excessive loss of dietary minerals due to excretion to the environment. A study was conducted with advanced sunshine bass fingerlings (130 - 150 g) to determine the apparent digestibility coefficients (ADCs) for various minerals in four rice products in extrusion-processed diets. Included in the study were brewers rice, rice bran produced from normal and mutant, low-phytate variety (K-Bonnet) of rice, and heat-stabilized rice bran (Equi-Jewel). Test diets consisted of a 70:30 mixture of reference diet to test ingredient with chromic oxide (1%) as the inert marker. Reference and test diets were preconditioned and extruded on a Wenger X-20 to produce a neutrally buoyant pellet (5 mm). The digestibility trials were conducted in eight 650-L round tanks connected as a closed recirculating brackish (5-7 ppt) water system. Diets were randomly assigned to tanks of 25-30 sunshine bass and fed twice daily to satiation. ADCs for protein, lipid, energy and various minerals in the four tested rice products will be presented and compared.