Separate and combined effects of cyclic fasting and l-carnitine supplementation in red porgy (Pagrus pagrus, L. 1758)

We examined the effects of cyclic fasting in red porgy (Pagrus pagrus) fed different dietary carnitine levels. Juvenile fish (23.58 ± 3.49 g) were divided into eight groups – four groups were fed every day to apparent satiation, while the other four were fasted for 7 days every 2 weeks. In each feeding regime, two replicates were fed an l-carnitine non-supplemented diet (46 mg kg−1) and the other two groups were fed an l-carnitine supplemented diet (630 mg kg−1). Fish fed 630 mg l-carnitine accumulated two times more l-carnitine in muscle than fish fed 46 mg l-carnitine. Cyclic fasting reduced the growth performance and lipid content in the liver. Carnitine supplementation did not affect performance and body composition, but decreased the n-6 PUFA content. Moreover, the combined effects of fasting and carnitine supplementation were observed on reducing the n-3 fatty acid content. Areas of steatosis were found in the livers of red porgy, but the results revealed that supplementation of l-carnitine in cyclic fasted fish contributed towards a lower degree of vacuolization than in fish fed to apparent satiation. Regardless of the feeding regime applied, the spleen of fish fed the l-carnitine-supplemented diet was haemorrhagic and hyper activation of melanomacrophage cells was observed.