Fituþol þorsks
Tilgangur þessarar rannsóknar var að kanna áhrif fituinnihalds í fóðri á vöxt og þrif í þorski af mismunandi stærð. Þekking á næringarþörfum fiska er nauðsynleg forsenda fyrir gerð fóðurs fyrir þá. Þorskar af tveimur stærðum (120 g og 600 g) voru fóðraðir (í þrítekningu) í 12 vikur á fóðri sem innihélt 10.0%, 13.5%, 21.2%, 24.5% og 27.7% fitu í þurrefni. Mismunandi fituinnihald hafði ekki áhrif á vöxt (SGR), holdstuðul (CF), flakanýtingu, fituinnihald í lifur eða fituinnihald í flökum. Í smærri fiskinum lækkaði fóðurstuðull (FCR) með aukinni fitu í fóðri. Fóðurfitan hafði ekki áhrif á fituinnihald innyfla án lifrar í smærri fiskinum(120g) en í 600 g fiski jókst fita í innyflum með auknu fituinnihaldi fóðurs. Fituinnihald hafði ekki áhrif á hlutfall slægðs þunga af heildarþunga í 600 g fiskinum en í smærri fiskinum lækkaði hlutfallið með aukinni fitu í fóðri. Lifrarhlutfall (HSI) í 600g fiski var ekki háð fituinnihaldi í fóðri, en hins vegar var jákvætt samhengi milli fóðurfitu og HSI í 120 g fiskinum. Þetta þýðir að fituþol þorsks með tilliti til lifrarhlutfalls er háð stærð fisksins.
Detailed knowledge of the nutritional requirements of fish is essential for feed formulation. The aim of this research was to investigate the effects of different lipid content in diets for Atlantic cod of different size. Cod of two size groups (initial weight 120 grams and 600 grams) were fed, in triplicate, for 12 weeks diets containing 10.0%, 13.5%, 21.2%, 24.5% and 27.7% lipid in dry matter. Different lipid content in the diet did not affect growth (SGR), condition factor (CF), fillet yield, lipid content in liver or lipid content in fillet. In the smaller fish, FCR was reduced with increased diet lipid. The lipid content in the diet did not affect the lipid content of intestines in the 120 grams fish but in the 600 grams fish there was a positive correlation between lipid content in diet and intestines. Dietary lipid did not affect gutted weight (calculated as the percentage of round weight) in the 600 grams fish but in the 120 grams fish, the percent gutted weight decreased with lipid content of the diet. The Heposomatic index (HSI) in the 600 grams fish was not affected by the lipid content of the diet but dietary lipid content significantly affected the HSI in the smaller fish. This indicates that the lipid tolerance of Atlantic cod, with respect to the effect on HSI, is size dependent.
