Project Number: 6028-31630-008-02-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Jun 1, 2016
End Date: Aug 31, 2019
1) Determine nutrient and amino acid availability for three protein concentrates in HSB for which the biochemical composition has been well defined; 2) Formulate, manufacture and feed test diets that maximize FM replacement levels in HSB in replicated tank trials; 3) Determine growth, body/fillet composition, and non-specific immune responses to the three concentrates in comparison to a FM-based reference diet; and 4) Determine the effect of 100% FM replacement with these concentrates on HSB resistance to a relevant bacterial disease challenge.
Digestibility and feeding trials with advanced juvenile HSB will be conducted at HKDSNARC using well-established protocols. In Year 1, digestibility trials will include a reference diet that meets the nutritional requirements of HSB and an indigestible marker, such as Yttrium. Three test diets will include one of three products of interest provided by the cooperator (Aqua-Pak 60™, Aqua-Pak 65™, and Aqua-Pak 70™) and will be formulated to contain a 70:30 mixture of reference diet to test ingredient. A fourth test diet will include 30% Menhaden FM as a control since expected nutrient digestibilities are well established for this ingredient. Test diets will be fed to triplicate groups (N = 30-50 fish/group) of HSB held in 600-liter tanks supplied with fresh well water at HKDSNARC. Fish will be fed their respective test diets for 7 days prior to fecal collection by manual stripping at optimal intervals post feeding. Fecal matter will be dried and analyzed for marker (Yt) and nutrient concentrations using standard methods of analysis to calculate nutrient digestibility. This will provide the Cooperator with nutrient and amino acid availability coefficients for the products of interest that will in turn be used by researchers and feed mills in formulating research and commercial diets for hybrid striped bass. In year 2, a completely randomized design growth trial will be conducted using a FM-based reference diet. The experimental variable in the growth trials will be protein level (60, 65, or 70%) of the Aqua-Pak™ product line on a digestible protein basis. All experimental diets will provide 40% digestible protein (DP) and 16% lipid and will formulated on an ideal protein basis to meet nutritional requirements of HSB. Fish will be stocked at 20-30/tank in three replicate tanks/diet and fed to satiation once daily for 8-12 weeks. Fish will be weighed periodically to track growth. At the trial conclusion a subset of 5 fish will be sampled from each tank, bled to conduct health assays and then ground for biochemical analysis of nutrient, energy, and amino acid retentions. A second set of 5 fish from each tank will be sampled for bioindices that include hepatosomatic index (HSI), intraperitoneal fat (IPF) ratio, and muscle ratio. Remaining fish will be reacclimated to their respective diets and then subjected to a bacterial challenge using standard protocols established at our lab. Responses will be analyzed in a mixed model ANOVA using Dunnett’s procedure to determine if there are differences (significance, P<0.05) in mean responses to the protein concentrates in comparison to the FM control diet. Additionally, a linear contrast will be used to determine if responses vary among protein levels of the products. Tukey-Cramer or Bonferroni’s multiple comparison test will be used to identify specific differences among treatment means. The results of the second year growth trial will be used to determine the biological value, limits of dietary ingredient inclusion, and provide the cooperator with insights for manipulating the composition of the protein concentrates to improve diet performance.