Lr Ward

Prospects of using marine actinobacteria as probiotics in aquaculture

Chemotherapeutic agents have been banned for disease management in aquaculture systems due to the emergence of antibiotic resistance gene and enduring residual effects in the environments. Instead, microbial interventions in sustainable aquaculture have been proposed, and among them, the most popular and practical approach is the use of probiotics. A range of microorganisms have been used so far as probiotics, which include Gram-negative and Gram-positive bacteria, yeast, bacteriophages, and unicellular algae. The results are satisfactory and promising; however, to combat the latest infectious diseases, the search for a new strain for probiotics is essential. Marine actinobacteria were designated as the chemical factory a long time ago, and quite a large number of chemical substances have been isolated to date. The potent actinobacterial genera are Streptomyces; Micromonospora; and a novel, recently described genus, Salinispora. Despite the existence of all the significant features of a good probiont, actinobacteria have been hardly used as probiotics in aquaculture. However, this group of bacteria promises to supply the most potential probiotic strains in the future.

The effect of feeding frequency on water quality and growth of the black tiger shrimp (Penaeus monodon)

Abstract The feeding strategy used in the commercial culture of shrimp can have a significant impact on pond water quality and hence growth, health and survival of the shrimp, as well as the efficiency of feed utilization. These factors contribute to the profitability of production and to the environmental impact of shrimp farming. The effect of four different feeding frequencies (3, 4, 5 and 6 feedings day −1 ) on the growth and survival of the black tiger shrimp, Penaeus monodon , and water quality was studied in an 8-week growth trial. The shrimp were held in 20×2500-l outdoor tanks containing water and sediment from a shrimp pond. The water management and aeration strategies were designed to simulate a shrimp pond system. The shrimp (initial weight of 5.6 g) were stocked at a density of 25 animals m −2 and fed a widely used, commercial pelleted feed, with all the feed being placed on feeding trays. The uneaten feed on the feeding trays was removed at specific time intervals so that in all treatments, the shrimp had access to the feed for 12 h day −1 . There were no significant ( P >0.05) differences due to feeding frequency on growth rate (1.4±0.08 g week −1 ), feed conversion ratio (FCR) (2.0±0.27) or survival (84±7.6%) of shrimp. Similarly, the water quality parameters (total N, ammonium, nitrate/nitrite, dissolved organic nitrogen, total phosphorus, phosphate, chlorophyll a , oxygen, pH, temperature, salinity, turbidity) were not different among treatments. The results suggest that there is no benefit from feeding P. monodon more frequently than 3 times day −1 when using a feed that is nutritionally adequate and has high water stability. Therefore, it may be possible to reduce feeding frequency in commercial shrimp ponds without adversely affecting water quality, shrimp growth rate and survival, thereby improving farm profitability.

Optimal dietary protein level for juvenile southern rock lobster, Jasus edwardsii, at two lipid levels

This study determined the effect on growth efficiency, nutrient retention and apparent digestibility of varying dietary protein concentration and protein/energy ratio for juvenile southern rock lobster, Jasus edwardsii. Isoenergetic diets were formulated at six crude protein levels (5% increments between 24% and 50%) and at each of two lipid levels (5% and 9%). Duplicate groups of 10 lobsters (initial weight mean 3.58 SE 0.86 g) were held in 50-l tanks, in a recirculating seawater system at 18 degrees Celsius and fed to 95% satiation over a 12-week growth trial. There were significant ( P < 0.05) differences in apparent crude protein digestibility (76.4-83.2%), but no difference in dry matter (mean 59.1 SE 0.8%) or energy digestibility (mean 77.7 SE 0.8%). Survival, feed intake, digestive gland index, protein efficiency ratio, energy efficiency ratio and whole-body composition were not significantly affected by dietary treatment. The relationship between nutrient intake and weight gain indicated optimal dietary digestible crude protein (DCP) levels of 29% and 31% when lobsters were fed diets containing 5% and 9% lipid, respectively. For the two lipid levels studied, the optimal dietary protein/energy requirement was similar for maximum weight gain (29 gDCP/ MJ DE) and feed conversion ratio (FCR, 30 gDCP/MJ DE).

Predicting glycogen concentration in the foot muscle of abalone using near infrared reflectance spectroscopy (NIRS).

Near infrared reflectance spectroscopy (NIRS) was used to predict glycogen concentrations in the foot muscle of cultured abalone. NIR spectra of live, shucked and freeze-dried abalones were modelled against chemically measured glycogen data (range: 0.77-40.9% of dry weight (DW)) using partial least squares (PLS) regression. The calibration models were then used to predict glycogen concentrations of test abalone samples and model robustness was assessed from coefficient of determination of the validation (R2(val)) and standard error of prediction (SEP) values. The model for freeze-dried abalone gave the best prediction (R2(val) 0.97, SEP=1.71), making it suitable for quantifying glycogen. Models for live and shucked abalones had R2(val) of 0.86 and 0.90, and SEP of 3.46 and 3.07 respectively, making them suitable for producing estimations of glycogen concentration. As glycogen is a taste-active component associated with palatability in abalone, this study demonstrated the potential of NIRS as a rapid method to monitor the factors associated with abalone quality.