Optimal Dietary Protein Requirement of Subadult Australian Hybrid Abalone (Haliotis rubra × Haliotis laevigata) at Different Rearing Temperatures

Abstract

Australian abalone aquaculture is characterised by a prolonged culture period and slow and variable growth, and abalone is cultured in fluctuating water temperatures ranging between 10 and 25°C with distinct seasons. Temperature is a crucial environmental factor influencing abalone’s physiology and energetics, leading to a change in nutritional requirements. However, feeds are generally formulated to match the nutritional requirements at their optimal temperature. Hence, there is a need to optimise dietary protein levels to match temperature-specific requirements during extreme conditions (winter and summer). Given this, a growth trial evaluating five experimental feeds consisting of graded protein inclusion levels (320, 350, 380, 410, and 440 g·kg−1) was conducted on subadult hybrid abalone (Haliotis rubra × H. laevigata) at three different temperatures reflecting winter (12°C), summer (22°C), and the annual average water temperature (17°C) for 143 days. At lower water temperature (12°C), there was a marginal improvement in growth performance as dietary protein levels increased from 320 to 440 g·kg−1. However, at higher water temperatures (when the culture water temperature is above 17°C), there was a significant improvement in growth performance as dietary protein levels increased from 320 to 440 g·kg−1 as evidenced by an improved weight gain, specific growth rate, and feed conversion ratio. Furthermore, increasing dietary protein levels did not compromise the nutritional quality of the abalone tissue at all three tested temperatures. Therefore, during periods of higher water temperatures, feeding Australian hybrid abalone with a relatively high dietary protein level (410 g·kg−1) is expected to result in improved growth, shorter culture duration, and profit maximisation.

Digestive enzymes of postweaned greenlip abalone (Haliotis laevigata) are influenced by water temperatures and dietary protein levels

“…Together, the growth response, protein utilisation and measured enzyme activity in the current study further support these past findings that higher temperature may drive the responses observed. Moreover, the nutrient utilisation of the same 6-month-old greenlip abalone supports the notion that these abalone use dietary protein for metabolic energy (Bansemer et al, 2015) and this is further improved by temperature (Hassan et al, 2023). Therefore, higher protease activity may contribute to superior growth rates at warmer water temperatures, which is supported by results in the current study.…”

“…In their study, the authors recommend a dietary protein level of 29% CP (21.9% digestible protein) with a digestible energy level of 12.5 MJ kg −1 for abalone at 14 • C and 17 • C. Bansemer et al (2015) suggested that increasing the crude dietary protein level to 35% may be beneficial as the water temperature increased. Similarly, Hassan et al (2023) reported that in subadult hybrid abalone (H. rubra × H. laevigata) of around ∼12.5 g initial weight grew best on a higher inclusion of dietary protein level. These authors concluded that ∼41% dietary protein levels would result in optimal performance.…”

“…Similarly, Hassan et al. (2023) reported that in subadult hybrid abalone ( H. rubra × H. laevigata ) of around ∼12.5 g initial weight grew best on a higher inclusion of dietary protein level. These authors concluded that ∼41% dietary protein levels would result in optimal performance.…”

“…Optimising dietary protein in formulated feeds is critical to improving the growth performance of abalone, ultimately leading to better utilisation and digestion (Bansemer et al., 2015; Britz & Hecht, 1997; Fleming et al., 1996; Hassan et al., 2023; Mai et al., 1995; Stone et al., 2013). In the current study we hypothesised that protease activity, measured as trypsin would be upregulated as dietary protein levels increased.…”

Growth performance and feed utilisation of Australian hybrid abalone (Haliotis rubra × Haliotis laevigata) fed increasing dietary protein levels at three water temperatures

“…However, no such studies concerning Australian hybrid abalone have been undertaken; therefore, it is unclear whether the Australian hybrid abalone also has size-specific protein requirements similar to the trends observed in other abalone species. Further, the recent finding on sub-adult Australian hybrid abalone related to better growth at higher temperature when fed on higher protein diet by the same authors ( 11 ) has prompted them to investigate whether the same growth potential may be attained in juvenile Australian hybrid abalone.…”