Abstract
l-Carnitine plays a key role in the regulation of energy metabolism and growth in fish. The aim of this study was to determine the effects of dietary l-carnitine levels on carnitine homeostasis and energy metabolism in diploid and triploid trout (Oncorhynchus mykiss). Diploid and triploid trout (29.5 ± 0.6 and 31.8 ± 0.5 g, respectively) were fed with three diets supplemented with 15, 200 or 530 mg l-carnitine/kg, respectively, for 56 days. Compared to 15 mg l-carnitine, total carnitine content increased in the liver by 182% in diploid and by 154% in triploid trout fed 530 mg l-carnitine. In muscle, total carnitine content increased by 60 and 73% in diploid and by 34 and 75% in triploid with the increase in dietary l-carnitine levels. l-Carnitine caused no significant change in the plasma concentrations of metabolites like proteins (ammonia, urea and protein), lipid (triglycerides), carbohydrate (glucose, lactate) and enzyme activities (lipase, lactate, alanine transaminase, lactic acid dehydrogenase). Triploid trout had significantly lower plasma ammonia (P = 0.003), lipase (P = 0.005) and triiodothyronine (T3; P = 0.003) levels than diploid trout. In conclusion, ploidy significantly affected the energy metabolism in rainbow trout, dietary l-carnitine levels altered the l-carnitine homeostasis, but not influence nutritional metabolism.
Highlights
IntroductionDuring the past three decades, aquaculture production has increased steadily, an average of 9% year, reaching a staggering 60 million tones (excluding aquatic plants and non-food products) in 2010 (FAO 2012)
During the past three decades, aquaculture production has increased steadily, an average of 9% year, reaching a staggering 60 million tones in 2010 (FAO 2012)
The aim of this study was to assess the effects of dietary L-carnitine levels on energy metabolism in diploid and triploid rainbow trout (Oncorhynchus mykiss)
Summary
During the past three decades, aquaculture production has increased steadily, an average of 9% year, reaching a staggering 60 million tones (excluding aquatic plants and non-food products) in 2010 (FAO 2012). Fish meal and fish oil derived from wild catches are dominant ingredients in aqua feed. It is estimated, at the present annual growth rates, that fishmeal supplies will be entirely consumed by the aquaculture sector by 2025. Plant protein ingredients have increasingly been used in diets of aquaculture species (Glencross Booth and Allan 2007), including carnivore marine species (Oliva-Teles and Goncalves 2001; Colburn et al 2012), is crucial the reduction of aquaculture farming dependent on fish meal. The replacement of fish meal may trigger, specific deficiency symptoms, including L-carnitine deficiency. Fishmeal may contain 10–20 times more L-carnitine than plant-based feeds (Ozorio et al 2001)
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