Performance of juvenile turbot (Scophthalmus maximus) fed varying dietary L-carnitine levels at different stocking densities

Abstract

Commercial farming of turbot (Scophthalmus maximus) at high stocking densities may lead to growth depression and increasing production costs. Moreover, the high levels of accumulated waste in an intensive system may cause rapid deterioration of water quality, which may undermine the production. Lcarnitine is known as a growth-enhancer which shows promise as mitigator of crowding effects. The effects of stocking densities (4, 8, 11 and 14 kg m -2 ) on growth performance, feed utilization and body composition were evaluated during 75 days on turbot (75.6 ± 2.8 g) fed two dietary L-carnitine levels (40 or 240 mg kg -1 ). At the end of the feeding trial, total ammonia excretion (TAN) was measured postprandially for 24h. Specific growth rate and weight gain decreased with increasing stocking density. Fish held at 4 kg m -2 had higher final body weight (94-96 g) than fish held at higher densities (80-87 g). Protein efficiency ratio was higher in fish held at 4 kg m -2 (1.33-1.36), in comparison to fish stocked at 8 kg m -2 (0.98) or 14 kg m -2 (0.45). Voluntary feed intake decreased from 0.70 to 0.56% BW with increasing stocking density. Dietary L-carnitine supplementation did not affect growth performance and body composition, except for body L-carnitine content which increased from 75 to 128 mg kg -1 BW with supplementation. Fish fed 240 mg L-carnitine supplements had lower TAN that the ones fed 40 mg L-carnitine (p < 0.05). Key words: compensatory growth, feed additives, stress, husbandry, nitrogen excretion Desempenho de juvenis de pregado (Scophthalmus maximus) em função da densidade de estocagem e de níveis dietéticos de L-carnitinaRESUMO: A aquicultura de pregado (Scophthalmus maximus) utilizando elevadas densidades pode reduzir o crescimento e aumentar os custos de produção. Elevados níveis de metabolitos gerados nestes sistemas intensivos provocam rápida deterioração da qualidade da água, podendo também comprometer a performance da produção. A L-carnitina atua como potenciadora do crescimento parecendo ser promissora por atenuar alguns desses efeitos. Os efeitos de densidades (4, 8, 11 e 14 kg m -2 ) no desempenho do crescimento, composição corporal foram avaliados em pregados (75,6 ± 2,8 g) alimentados durante 75 dias a dois níveis dietéticos de L-carnitina (40 ou 240 mg kg -1 ). Após esse período, determinou-se a excreção de amônia pós-prandial durante 24 horas. Os peixes cultivados na menor densidade, 4 kg m -2 , apresentaram melhores taxas de crescimento e ganho de peso (94-96 g) em comparação aos mantidos em altas densidades (80-87 g). A taxa de eficiência proteica foi mais elevada a 4 kg m -2 (1,33-1,36), do que a densidades de 8 kg m -2 (0,98) ou 14 kg m -2 (0,45). A ingestão voluntária de alimento decresceu de 0,70 para 0,56% do peso corporal com o incremento da densidade. A suplementação de carnitina não afetou o crescimento e a composição corporal, com exceção do conteúdo de carnitine da carcaça que passou de 75 a 128 mg kg -1 . Peixes alimentados com suplementos de 240 mg L-carnitina apre...

The metabolic regulation of dietary L‐carnitine in aquaculture nutrition: present status and future research strategies

“…; Gonçalves et al . ). Many studies have shown that supplementing L‐carnitine in diets exhibits a positive growth‐enhancing effect in fry or juvenile fishes.…”

Performance of pacu juveniles fed diets supplemented with L-carnitine

“…However, it may promote the energy efficiency of fatty acids, due to the increased mitochondrial lipid oxidation. It should be noted that the obtained results may differ according to experimental conditions, studied species, fish development phase, stress conditions, among other factors (Gonçalves et al, 2010). Li et al (2020) found that the action of L-carnitine supplementation in fish diets is directly linked to the abundance of individual macronutrients, including fatty acids, glucose, and amino acids.…”

“…Several authors have reported the positive effects of L-carnitine on some fish species, including: improved growth, reduction of muscle fat, better response against stress due to confinement, and adaptation to high levels of ammonia and high temperature variations (Gonçalves et al, 2010;Yang et al, 2012). However, the literature also shows contradictory results, which may be related to differences among the studied species, such as experimental conditions, management, and leaching and levels of the supplemented L-carnitine, among others (Gonçalves et al, 2010). Despite these reports, there are still no known studies on the inclusion of L-carnitine in the diet of pacu (Piaractus mesopotamicus Holmberg, 1887), which is native to South America and has an opportunistic omnivorous food habit, being well adapted to different production systems (Vaz et al, 2000).…”