Matthew S. Bansemer

DIETARY PROTEIN LEVEL AND WATER TEMPERATURE INTERACTIONS FOR GREENLIP ABALONE HALIOTIS LAEVIGATA

ABSTRACT Land-based grow-out of greenlip abalone (Haliotis laevigata) in Australia is predominantly practiced using a single-diet feeding strategy, despite geographical and seasonal differences in water temperature that influence feed intake and growth. This 12-wk study investigated the interactions between 2 abalone year classes (1 y old, 1.8 g; 2 y old, 22.9 g), 3 water temperatures (14°C, 18°C, and 22°C), and 4 dietary protein levels (1 y old: 27%, 30%, 33%, and 36% crude protein; 2 y old: 24%, 27%, 30%, and 33% crude protein) to evaluate the potential to use diets to suit specific water temperatures and aged animals. Diets were formulated to be isoenergetic (∼12.5 MJ/kg digestible energy), and contain fat levels of ∼3.6% and digestible protein levels ranging from 17.99%–28.57%. Feed was fed to excess daily and uneaten food was collected. Temperature significantly affected the specific growth rate of both year classes of abalone. There was no significant effect of dietary protein level on specific growth rate; however, abalone compensated for a reduction of dietary protein by consuming more feed. This observation was evident with significant increases in feed conversion ratios as dietary protein levels decreased for both year classes. With the exception of abalone grown at 14°C, when protein deposition decreased with increasing dietary protein level, protein deposition increased with an increase in dietary protein for both year classes. For 1-y-old abalone, as temperature increased from 14-22°C, the optimum crude dietary protein levels increased from -29%-∼35%. For 2-y-old abalone, the optimum crude protein level appeared to be less, and increased from 24% at 14°C to 34% at 22°C. There is scope to use multidiet feeding strategies in the production of greenlip abalone.

Restricting feed ration has more effect than diet type on the feeding behaviour of greenlip abalone Haliotis laevigata

Abalone farmed in Australia are predominantly fed formulated feeds, while in the wild, their diet consists of a mix of macroalgae. Here we investigated the feeding behaviour of juvenile greenlip abalone, Haliotis laevigata; fed live macroalgae and formulated diets at different rations; and observed their feeding behaviour using a novel ventral video monitoring technique. Four different diets (commercial chip, experimental flake, Ulva sp. and Gracilaria cliftonii) at two feeding rations (excess vs. restricted) were tested. Diet type had no effect on abalone movement, but macroalgal diets resulted in higher feed intakes. Restricting feed rations induced greater movement. Abalone moved little during the light period and moved mostly during darkness, except for animals on the restricted feed ration where feeding commenced during the light period. On farms, this phenomenon may be a useful behavioural indicator for identifying underfed abalone. Despite their lower intake, formulated diets promoted higher energy and nutritional intake, indicating that quantity of feed consumed is not solely indicative of nutritional gain. From a research perspective, the novel ventral monitoring method has created opportunities for further behavioural studies in molluscs.

Comparative Histological Changes in the Greenlip Abalone Haliotis laevigata Gastrointestinal Tract in Response to Water Temperature, Different Dietary Protein Levels, and Animal Age

ABSTRACT The land-based culture of greenlip abalone Haliotis laevigata in southeastern Australia is carried out using seawater that is prone to seasonal temperature fluctuations and is done almost exclusively using artificial feeds. Although some nutrition research has been done to identify the optimum dietary protein level, typically farms use only 1 diet for grow-out after the juveniles are weaned. Little consideration has been given to the effects of fluctuating water temperatures and dietary protein levels on the morphology of the gastrointestinal tract (GIT) of abalone. Because these factors are known to impact growth in other aquatic species, it is important that they are investigated further to improve growth in abalone species. In this study, the histological changes of the GIT of greenlip abalone in response to 2 water temperatures and 4 dietary levels of crude protein (juvenile, 27% and 36%; subadult, 24% and 33%) for juveniles (1.75 g) and subadults (22.93 g) were investigated. The epithelial thickness of the stomach and crop; intestinal villus height, width, and area; lamina propria height; and stomach, crop, and intestinal neutral and acidic goblet cell numbers were measured. The stomach epithelium was significantly thicker at 14°C than 22°C in both juveniles and subadults, whereas the crop epithelium was significantly thicker at 22°C than 14°C in juveniles. The crop epithelial thickness of subadults was reduced by increasing dietary protein; however, juveniles did not show the same response. Juvenile abalone were more sensitive to temperature fluctuations than subadults, whereas significant effects of dietary protein levels were only observed in subadults. The alterations in the morphology of the GIT did not appear to be detrimental to the health and growth of the abalone. Further research is required to investigate the interactive effects of water temperature and dietary ingredients, particularly in regard to antinutritional factors, on the morphology and function of the GIT to improve our understanding of abalone physiology.

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.

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.

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.