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Energy Requirements/growth

Energy Requirements/growth. Daily energy requirement (kcal/unit bwt) Overall energy requirement/fish increases with size (related to increased biomass) Metabolism – Requires energy (nutritional) reproduction, maintenance and growth. Energy Requirements/growth. Metabolism (cont.)

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Energy Requirements/growth

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  1. Energy Requirements/growth • Daily energy requirement (kcal/unit bwt) • Overall energy requirement/fish increases with size (related to increased biomass) • Metabolism – • Requires energy (nutritional) • reproduction, maintenance and growth

  2. Energy Requirements/growth • Metabolism (cont.) • Gross energy (GE) – • Digestible energy (DE) – energy available for metabolism and growth • DE = GE – FE (fecal energy) • Metabolizeable energy (ME) – • Can be affected by env. conditions – respiration energy (RE) and energy in urine/gills (UE) • ME = DE – (RE + UE)

  3. Energy Budget Basal/heat met. increase (swimming E) Fecal Energy Metabolized Gross Energy Recovered (tissues, gametes) Digestible Energy Excreted (urine, gills, Body surface)

  4. Food Conversion Ratio (FCR) • FCR = Feed fed (dry wt. basis)/weight gain • amount of feed to produce one unit weight gain • Fish – very efficient converters (FCR’s < 1.0) • To estimate FCR for feed being used: • FCR = E/(ME * 1000) • E: metabolizeable kcal required for 1 unit weight gain • ME: kcal per g of feed

  5. Feeding rates • Do not overfeed!! • Fish fed ad libitum or on a % body wt basis • Feed to satiation? • Calculation of daily feed requirements: • Adjust based on estimated growth (% daily gain) • Should adjust as often as possible • Feeding tables – based on length and temperature

  6. Feeding rates • Methods to calculated feeding rates: (can be based on length or weight increases) • Method#1 (assumes linear growth rate) • Wt = Wo + F/C • Method#2 (assumes logarithmic growth) • Wt = Woekt

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