Growth and feed utilisation of juvenile greenlip abalone (Haliotis laevigata) in response to water temperatures and increasing dietary protein levels

In this 91-day study, the interaction between four dietary crude protein (CP) levels (27, 30, 33 and 36% CP) and three water temperatures (14, 17 and 20 degrees C) on the growth and feed utilisation of 6-month old greenlip abalone (Haliotis laevigata) (0.91 g) were investigated. Diets were formulated to be isoenergetic (12.5 MJ kg(-1) digestible energy), containing a lipid level of similar to 3.6% and digestible protein from 17.99 to 28.57%. Abalone were fed to excess at 16:00 h daily, and uneaten feed was collected the following day. The specific growth rate (SGR) of abalone improved significantly as water temperatures increased from 14 to 17 to 20 degrees C. In addition, apparent protein deposition was significantly higher in abalone at 17 and 20 degrees C compared to abalone at 14 degrees C. There was no significant effect of dietary protein level on SGR, but faster growing abalone at 20 degrees C compensated by consuming more feed when fed low dietary protein levels. In contrast, a significant positive relationship was observed between dietary protein level and feed consumption rate in slower growing abalone at 14 and 17 degrees C. A nonsignificant tendency for the apparent feed conversion ratio (FCR) to improve was observed in abalone fed high protein diets at 20 degrees C, while at 14 degrees C, abalone had a significantly poorer FCR, especially when fed high dietary protein levels. Based on results from the current study, it is plausible to heat land-based nursery systems in order to gain accelerated growth of juveniles before transfer to grow-out systems. Additionally, no benefits were apparent by feeding abalone high protein diets at 14 or 17 degrees C, and we therefore recommend a dietary protein level of 29% CP at 14 and 17 degrees C. While the SGR of abalone at 20 degrees C was not significantly influenced by dietary protein, the feed consumption rate decreased and there was a tendency for FCR to improve as dietary protein level increased. Therefore, it may be beneficial for abalone to be switched to a diet containing similar to 35% CP at water temperatures >20 degrees C. (C) 2014 Elsevier B.V. All rights reserved.