Effect of feeding intensity and feed composition on nutrient digestibility and production performance of common pandora (Pagellus erythrinus) in sea cages

Fish were grown from a weight of 66.9 g to 211, 194, 217, and 204 g with LL100, LL75, HL100, and HL75 treatments, respectively. Fish from each cage were weighed monthly and feed consumption and performance parameters were calculated for each consecutive rearing period. Daily feed intake (DFI) at satiation was higher for low than high lipid diet, while at restricted feeding, DFI did not differ. Fish weight did not differ between HL100 and LL100 treatments, while at restricted feeding fish fed HL grew faster than those fed the LL diet. As temperature dropped and fish weight increased, specific growth rate (SGR) declined from an average of 0.84 to about 0.2 from the beginning to the end of the rearing period. Thermal-unit growth coefficient (TGC) declined as well but at a slower rate than SGR. Feed efficiency (FE) was similar for both diets at any feeding level, while it was systematically higher for the restricted than the satiation fed groups. Results of apparent net protein utilization (ANPU) and protein efficiency ratio (PER) did not indicate a protein sparing by lipid, the only exception being the last period of rearing when LL100 indicated a significantly lower ANPU than HL100. Apparent protein and starch digestibility of the HL (93 and 95.4%, respectively) were higher than the respective values of the LL diet (91.4 and 92.4%, respectively) possibly due to the higher starch content of the second. Cost benefit analysis revealed that, in common pandora rearing, the use of a HL diet was more cost efficient than the use of a LL diet in both feeding levels tested with a net economic benefit of 1.59, 1.56, 1.76, and 1.81 € per kg of fish produced for LL100, LL75, HL100, and HL75 treatments, respectively.