View related articles View Crossmark data Citing articles: 8 View citing articles Growth performance and product quality of meagre (Argyrosomus regius) fed diets of different protein/lipid levels at industrial scale

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The effect of feed deprivation at four water temperatures (17, 20, 23, 26 °C) was investigated in meagre (Argyrosomus regius) of initial mean weight ± SD, 116.16 ± 4.74 g, in triplicate groups. Fish were deprived of feed for a period of 60 days and sampled on days 0, 14, 41, and 60, during which body weight, specific growth rate, somatic indices, muscle proximate composition, plasma metabolite levels (total lipids, proteins, cholesterol, triglycerides, glucose), and liver and muscle enzymatic activities [L-lactate dehydrogenase (L-LDH), citrate synthase (CS), malate dehydrogenase (MDH)] were evaluated. Long-term feed deprivation resulted in a significant decrease in body weight, condition factor (CF), hepatosomatic index (HSI), muscle lipids, and plasma metabolites (all except proteins) and increase in muscle moisture. Plasma glucose concentration decreased with time and became significantly lower at 41 and 60 days. Glucose concentration and weight loss expressed a different response in the short term (14 days) than in the long term (14 and 60 days) of feed deprivation, suggesting a change in glucose metabolic profile. After 60 days of feed deprivation, there was an increase in the L-LDH activity in the liver at all temperature levels, which reflects a rising glycolytic potential by activating the carbohydrate metabolism and an ATP-dependent demand. MDH activity increased in the liver and muscle, except at 17 °C in the muscle, which indicates aerobic glycolysis and lipolysis. CS activity in the liver increased after the 60 days, whereas that in the muscle decreased, indicating the muscle is less dependent on aerobic oxidation for energy reserves.

The shi drum, Umbrina cirrosa, is considered quite promising candidate and emerging alternative Mediterranean aquaculture species to the dominant, European seabass, Dicentrarchus labrax, and gilthead seabream, Sparus aurata, due to its high growth rate and feed efficiency (Segato, Corato, Fasolato, & Andrighetto, 2005). Shi drum feeds mainly on invertebrates and fish (Abellan & Basurco, ), suggesting that this species has high protein requirements. Moreover, the shi drum has a good adaptation capacity to culture conditions and, unlike the winter reproducers seabass and seabream, it is a spring-summer reproducer (Mylonas et al., 2004), thus providing a good species to grow in parallel with the existing cultivated species. Shi drum is a demersal fish, member of the Sciaenidae family (Nelson, Grande, & Wilson, 2016), living on the sandy bottom of maximum 100 m depth, and is distributed all around the Mediterranean Sea area, including the Black Sea. The size of the shi drum during catch is usually around 50-60 cm, but it can reach up to 1 m length and 12 kg weight (Mylonas et al., 2000a). In aquaculture settings, this species can achieve a weight of 500 g in only 15 months, which is near twice the growth rate of seabass and seabream (Fabi & Fiorentini, 1993; Mylonas et al., 2000b), thus making the shi drum a very attractive species for aquaculture. AbstractThe shi drum is an emerging Mediterranean aquaculture species that has gained increasing interest in recent years. However, the nutrient requirements of this species remain to be determined to optimize its culture. The present study evaluated the effects of dietary protein (470g/kg or 520g/kg) to lipid ratios (100g/kg, 150 or 200g/ kg) on the growth performance, nutrient utilization and tissue morphology of the shi drum (7 g average initial weight). Dietary protein levels positively correlated with weight gain, showing high protein demands (>470g/kg) for this species. Nonetheless, dietary lipid levels negatively affected growth rate, feed intake and efficiency, and protein utilization, suggesting that this macronutrient cannot be efficiently utilized in high concentrations (>100g/kg). Histological evaluation revealed fat accumulation within the hepatocytes and the enterocytes with increasing dietary lipid levels, starting from 150g/kg lipid inclusion. Overall, our results confirm the high dietary protein requirements of the shi drum (>470g/kg for fish of 7 g initial weight) and suggest that lipid levels should not exceed 100g/kg of inclusion in the diets as this species has a low tolerance to this macronutrient. K E Y W O R D Sdiversification, emerging aquaculture species, feed utilization, growth performance, histological score, nutrient requirements | 445 KOKOU et al.

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