Krishna-Lee Currie

Temperature-Dependent Feed Consumption Patterns for Greenlip (Haliotis laevigata) and Hybrid (H. laevigata × Haliotis rubra) Abalone Fed Fresh Macroalgae or a Formulated Diet

ABSTRACT Because of the nocturnal and slow feeding activity of abalone, farmed abalone are typically provided with feed throughout the night. Understanding the nocturnal feeding patterns of abalone is fundamental to feed management and productive abalone farming. In this study, the apparent feed consumption for greenlip abalone (Haliotis laevigata) and hybrid abalone (H. laevigata3Haliotis rubra) fed fresh Ulva sp. or a commercial formulated diet at 18°C or 22°C were investigated at night. Abalone were exposed to low light intensity (3.4 Lux) from 7:00 AM to 7:00 PM and darkness from 7:00 PM to 7:00 AM. Abalone were fed to excess daily at 4:00 PM and feed intake was determined at 7:00 PM, 10:00 PM, 1:00 AM, 4:00 AM, and 8:00 AM. When Ulva sp. was added to the tank, greenlip and hybrid abalone immediately displayed a feeding response, which was not observed in abalone fed the formulated diet. Abalone consumed Ulva sp. at a linear rate from 4:00 PM to 8:00 AM. In contrast, the apparent feed consumption rate of abalone fed the formulated diet was minimal from 4:00 PM to 7:00 PM, and was highest between 7:00 PM and 1:00 AM. Apparent feed consumption rate of abalone significantly increased as water temperature increased from 18°C to 22°C, but the effect was greater for hybrid abalone compared with greenlip abalone. The total apparent feed intake of both greenlip and hybrid abalone fed Ulva sp. was significantly greater than for both types of abalone fed the formulated diet. The total apparent feed intake on dry basis, and nutrient intake for abalone fed Ulva sp. was significantly lower than for abalone fed the formulated diet. This study indicates that the upper temperature range for feed intake in hybrid abalone is higher than in greenlip abalone. Ulva sp. can stimulate abalone feeding, though the high moisture content in algae can reduce nutrient intake.

Ventral Videographic Assessment of the Feeding Behavior of Juvenile Greenlip [Haliotis laevigata (Donovan, 1808)] and Hybrid (H. laevigata×Haliotis rubra) Abalone in Response to Dietary and Temperature Manipulation

ABSTRACT This multifactorial study used a newly developed ventral videography technique to investigate the feeding behavior of 18-mo-old juvenile greenlip abalone (21.1 g, 55.6 mm), and hybrid abalone (23.4 g, 57.6 mm) fed either a formulated commercial diet or live Ulva sp. at 18°C and 22°C. Feeding behavior was scored in terms of the following activities: quiescence, alertness, moving, feeding, distance traveled, velocity, and homing. There was a significant effect of diet type and temperature on feeding behavior of abalone. Both types of abalone were more active and exhibited the highest velocity when fed the formulated diet at 22°C. Greenlip abalone spent a larger proportion of time feeding on Ulva sp. than on the formulated diet, regardless of the water temperature. In contrast, no significant difference was observed in the proportion of time feeding between diet types for hybrid abalone. Both types of abalone rapidly located and consumed Ulva sp. when feed was introduced into the aquaria at 1600 h (light phase). In contrast, abalone predominantly commenced feeding on the formulated diet in the dark phase, indicating the potential of Ulva sp. as feed attractant in abalone diet, to promote feeding. The mode in which abalone consumed feed also differed between diets. Abalone fed the formulated diet nibbled intermittently on random chips, whereas when fed Ulva sp., abalone engulfed entire individual fronds before moving on to the next available frond. Greenlip and hybrid abalone exhibited homing behavior at the completion of the dark phase, which was more pronounced in abalone fed Ulva sp. This new information may assist in refining feed design and feeding practices for the culture of these two types of abalone.

Impact of Vitamin K1 on Tissue Vitamin K Levels, Immunity, and Survival of Greenlip Abalone, Haliotis laevigata, at Summer Water Temperatures

ABSTRACT Summer mortality impacts the productivity of greenlip abalone, Haliotis laevigata, on land-based farms in South Australia. It is associated with high water temperature (greater than 23°C), low dissolved oxygen levels, increased bacterial loads, and immune system suppression during summer months. This study aimed to alleviate mortality rates of greenlip abalone by dietary intervention using vitamin K1 to support the innate immune system and oxidative status. Dietary vitamin K1 at 0.0, 0.5, 1.0, and 5.0 mg kg-1 was added to a commercially formulated diet mash. An additional diet containing 0.5 mg kg-1 of K3 was also used for comparison. Diets were fed to 3-y-old abalone (71.51 g; 79.91 mm) at 22 and 25°C water temperatures for 39 days. No mortalities were observed at 22°C; however, high mortalities were observed in all dietary treatments at the water temperature of 25°C. Compared with the negative control diet (0.0 mg additional inclusion ofK1 or K3 kg-1) at 25°C, the inclusion of vitaminK1 orK3 did not improve survival of greenlip abalone (P > 0.05). VitaminK1 inclusion level resulted in significant increases in vitamin K1 concentration of visceral organ and muscle tissues (P < 0.05). Steady-state levels of vitamin K1 were not reached. Steady-state levels of K2-MK-4 in visceral organ and muscle were reached when analyzed levels of dietary vitamin K1 reached 0.02 mg kg-1. This was also true for K2-MK-7, but in the visceral organ only. Vitamin K1 inclusion level did not significantly affect total hemocyte count, phagocytic activity, or phagocytic index (P > 0.05). Increasing water temperature to 25°C resulted in significant increases in serum catalase activity (22 < 25°C) and vitaminK1 concentration in muscle tissue (22 < 25°C). Comparison of vitamin K1 or K3 at 0.5 mg kg-1 resulted in significant changes to serum catalase activity (K1 > K3) and vitamin K1 concentration in visceral organ (K1 >K3). In conclusion, vitaminK1 at the doses tested, resulted in significant increases in vitaminK1 concentration in visceral organ and muscle tissues, but failed to improve immune function, oxidative status, or survival of greenlip abalone at high summer water temperatures.

Growth and Nutrient Utilization of Greenlip Abalone (Haliotis laevigata) Fed Ulva Sp. Protein Extract

ABSTRACT Greenlip abalone (Haliotis laevigata) are commercially farmed in land-based systems in southern Australia and are fed formulated diets that typically do not contain macroalgae. In a 90-day study, the growth and nutrient utilization of juvenile greenlip abalone (1.82 g, 23.23 mm) fed diets containing Ulva sp. protein extract (UPE) were investigated. Animals were fed one of the four formulated test diets containing graded levels of UPE (0%, 5%, 10%, and 20%) or a commercial diet that served as a control for the 0% basal diet. Diets were formulated to contain 37% crude protein, 5% lipid, and 17.5 MJ/kg gross energy. The specific growth rate and shell growth rate (µm/day) of abalone fed the four experimental diets were similar. Dietary inclusions of UPE supported the growth of juvenile greenlip abalone and may be used to reduce dietary inclusions of solvent extracted soybean meal, dehulled lupins, and wheat flour. Currently, UPE is cost prohibitive for commercial use in greenlip abalone diet. As UPE is a by-product of the macroalgae industry, the cost of UPE would likely become more economically viable as macroalgae production increases in the future to include in diets for greenlip abalone. Once economically viable, we recommend a dietary inclusion of up to 20% UPE meal for greenlip abalone.

Survival and Feeding of Greenlip Abalone (Haliotis laevigata) in Response to a Commercially Available Dietary Additive at High Water Temperature

ABSTRACT Elevated mortality, triggered by increased water temperatures (>22°C) and associated factors, is a significant issue for land-based abalone farms in southern Australia. The aim of this study was to test the efficacy of the commercial animal feed product Orego-Stim (OS), containing oregano essential oil in reducing the mortality of 3-y-old greenlip abalone (Haliotis laevigata) exposed to high water temperature (25°C). Inclusion levels of 0.0 (commercial control diet), 0.5%, 1.0%, 2.0%, and 4.0% OS were added into a commercial feed formulation and diets were fed to 3-y-old greenlip abalone (67.98 g, 77.01 mm shell length) at two water temperatures (22°C and 25°C) for 47 days. Survival and immune parameters including phagocytic activity, total hemocyte count (THC), and activities of the enzymes superoxide dismutase (SOD) and catalase (CAT) were measured. Survival was high at 22°C with no significant differences in mortality between treatments. Irrespective of this, exposure to elevated water temperature (25°C) resulted in significantly higher mortalities for all diet treatments (P < 0.05), without any effect of diet. Low ferric reducing antioxidant potential values were observed for all diets. Phagocytic activity remained stable for all temperature and OS treatments (48.82% ± 1.31%). The dietary inclusion of OS and increased water temperature increased the THC compared with the commercial control diet treatment at 22°C. Superoxide dismutase was significantly elevated in greenlip abalone fed the commercial control (0.56 ± 0.08 U mL-1), and CAT was significantly higher when fed the 4.0% OS diet treatment at 25°C (18.93 ± 2.25 nmol min-1 mL-1). Despite failing to increase survival, OS significantly enhanced feed intake at both temperatures at 2.0% and 4.0% compared with the commercial control diet treatment, highlighting its ability as a feeding stimulant (P < 0.05).

Increased Dietary Protein Improves the Commercial Production of Hybrid Abalone (Haliotis laevigata × Haliotis rubra)

ABSTRACT Over the past decade, Australian abalone were produced using a range of commercially formulated grow-out diets with crude protein (CP) levels ranging from 27% to 30% throughout their production cycle. Recent research identified higher optimal dietary CP levels of greater than or equal to 35%for younger than 1-y-old abalone at higher water temperatures (20–22°C). To validate the results of the laboratory-based research, the current trial was designed to investigate the effect of feeding two different commerciallymanufactured diets (standard-protein diet, 32%CP, versus a high-protein diet, 39%CP) to hybrid abalone (Haliotis laevigata ×Haliotis rubra; initial weight: 3.10 g) on growth performance, feed utilization, and sales revenue under on-farm conditions. During this 18-mo trial, abalone were cultured using normal commercial practices over two summer periods at Great Southern Waters abalone farm (Indented Head, VIC, Australia). A significant improvement in specific growth rate (SGR) led to a 9% improvement in biomass gain for abalone fed with the high-protein diet. This improvement was achieved with no differences in survival, and minimal difference in feed input between diets. In addition, the feed conversion ratio of abalone fed with the high-protein feed was 7.1% superior to that of animals fed with the standardprotein diet. On the basis of a farmgate value ofAUD35/kg abalone, for an additional feed input cost ofAUD2/m2 slab tank/y, a 9.5%increase in basic annual sales revenue (AUD44/m2 slab tank/y) was achieved feeding the high-protein diet. In addition, due to an increased SGR by feeding the high-protein diet, the duration of a typical 3-y production cycle for hybrid abalone may be shortened by up to 3.4 mo. By adopting the high-protein diet, farmers may also harvest abalone sooner, and reduce exposure to one less summer. This may reduce heat-related mortalities and further improve productivity, and when combined with savings made with biomass and feed efficiency gains, a more than 10%improvement in productivity across the entire grow-out period for hybrid abalone may be achieved.