The effect of pellet texture on the feeding behaviour of gilthead sea bream ( Sparus aurata L.)

Abstract

The aim of this study was to investigate the behaviour of gilthead sea bream when fed control and soft-textured pellets, to determine whether the immediate feeding response to a softer pellet resulted in less manipulation of the pellets during feeding, increased consumption, and reduced waste from handling. Individual feed intakes were calculated from radiographs and the proportion of unaccounted ballotini beads used to estimate waste production from chewing. The proportion of feed particles to unbroken pellets in the stomach was also measured. Food handling behaviour (chewing rate, number of bream chewing, and ejecting pellets) was recorded using an underwater camera. When fed the soft-textured pellets, a greater proportion of feed particles in the stomach was found in comparison to when the control diet was fed ( P<0.001). This implies that sea bream crush softer pellets more effectively. This was further supported by the soft-textured diet eliciting a lower rate of chewing ( P=0.001). There was a trend for the proportion of feed particles extracted from the stomachs of bream fed on the control diet to increase over time ( P=0.001), resulting in the difference in the proportion of feed particles in the stomachs between diets lacking significance in the final sample days. This may be related to either increasing body size and development of dentition resulting in greater crushing power or the bream may have learnt over time to crush the pellets more effectively. The results suggest that bream can crush softer pellets more effectively, but with no impact on waste production or feed intake. The results are discussed in relation to the design of pellets to optimise production efficiency, product development, and waste reduction in sea bream aquaculture.