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Abstract A 32-day comparative feeding trial was performed to evaluate the nutritional value of four different ray fish liver oils to the Pacific white shrimp Litopenaeus vannamei. Four feeds were prepared with liver oil extracted from Dasyatis brevis, Rhinoptera steindachneri, Aetobatus narinari, and R. bonasus. A control feed was prepared with Menhaden fish oil. Ray fish liver oils were mainly composed of poly- and highly unsaturated fatty acids and contained levels of 20:5n-3 and 22:6n-3 comparable in magnitude to those of Menhaden fish oil, except for A. narinari liver oil, which had moderately low concentrations of 20:5n-3 and 22:6n-3 but showed a particularly high level of 20:4n-6, more than six times greater than that of Menhaden fish oil. Dietary fatty acids significantly influenced the fatty acid composition of shrimp muscle tissue, e.g., the diet with Menhaden fish oil elicited significantly higher shrimp muscle DHA level than diets with oil from D. brevis, and A. narinari, but not than diets with oil from R. steindachneri and R. bonasus. In spite of these differences, all four ray fish liver oils evaluated were as efficient in promoting growth and survival of L. vannamei as Menhaden fish oil, an ingrethent known for its adequate nutritional quality to shrimp and fish. This study demonstrated one of the many possible applications of a locallyavailable resource that is currently being wasted.
Keywords Litopenaeus vannamei * Ray fish · Liver oil Fatty acids
Introduction
Fish oil is a commonly used ingrethent in shrimp and fish feed manufacturing. High nutritional value, as it provides essential fatty acids, as well as enhancement of feed palatability are two of the most important reasons for its inclusion. It was estimated that 924,426 tonne offish oil were produced worldwide in year 2003, of which 86.8% was utilized by aquaculture. Of this amount, 471,000 tonne (over 50%) were destined for production of salmon feed, followed by feeds for trout (15.4%), cod, tuna and other marine fishes (13.8%), shrimp (7.3%), and different species of carp (5.5%) [1]. However, fish oil production has remained relatively constant over the past years and it is not expected to increase [2], meaning that it will not be able to meet the demand from the aquaculture industry, which is growing at a fast pace....