Evaluation of Hydrogenated Soybean Oil in Feeds for Hybrid Striped Bass Fed in Conjunction with Finishing Periods of Different Durations

We evaluated the production performance and tissue composition of hybrid striped bass, i.e., sunshine bass (female White Bass Morone chrysops × male Striped Bass M. saxatilis (initial weight = 110.6 g) raised to a marketable size (final weight = 575 g) on grow-out feeds containing graded levels of fish oil and hydrogenated soybean oil (100% fish oil, 50% fish oil and 50% soybean oil, 25% fish oil and 75% soybean oil, or 100% soybean oil) in conjunction with finishing periods of different durations (4, 8, or 12 weeks of feeding the 100% fish oil feed prior to harvest). Production performance varied significantly among the feeding regimens, but none of the experimental groups were significantly different from the 100% fish oil control group. However, performance tended to follow fish oil consumption, with regimens providing more fish oil during grow-out yielding marginally superior growth and growth efficiency. Fillet fatty acid profiles varied considerably among the regimens prior to finishing. Fillets of fish fed diets containing increasing amounts of hydrogenated soybean oil contained more monounsaturated fatty acids (18:1[n-9]) and (n-6) and fatty acids (18:2[n-6]) and less long-chain polyunsaturated fatty acids and (n-3) fatty acids (20:5[n-3] and 22:6[n-3]). Despite major differences in dietary levels of saturated fatty acids (SFAs), fillet levels of SFAs did not vary appreciably. Profile differences arising during grow out were reversed by finishing, to a greater or lesser extent, depending on the magnitude of prefinishing profile distortion and the duration of the finishing period. Utilization of hydrogenated soybean oil merits further consideration and research, but our results suggest that this feedstuff has value as a supplemental lipid source, if not a complete fish oil substitute, in feeds for hybrid striped bass.