Imad Patrick Saoud

An ex vivo approach to studying the interactions of probiotic Pediococcus acidilactici and Vibrio (Listonella) anguillarum in the anterior intestine of rainbow trout Oncorhynchus mykiss

The aim of the present study was to observe the antagonistic relationship of the probiotic Pediococcus acidilactici and the pathogen Vibrio (Listonella) anguillarum in the intestine of rainbow trout (Oncorhynchus mykiss) by using an ex vivo intestinal sac method. Rainbow trout (240-250g) were fed either a control diet (commercial diet: 43% protein, 20% lipid) or a probiotic diet (control diet supplemented with P. acidilactici (Bactocell) at log 7 CFU g -1 ) for two weeks. The anterior intestine was then isolated for an ex vivo challenge study and intestinal sacs formed by shutting one end of the intestinal portion. The sacs were filled with PBS solutions containing either no bacteria (as a control), the probiotic (P. acidilactici), the pathogen (V. anguillarum), or probiotic+pathogen and incubated for one hour. At the end of the exposure bacterial levels in the lumen were determined by culture based approaches and colonisation of the mucosa assessed with PCR-DGGE and electron microscopy (EM). Intestinal morphology (observation of gross morphological damage, ultrstructural differences and the quantification of goblet cells and intra epithelial lecuocyte numbers) and bacterial infection/translocation was assessed using light microscopy (LM) and EM. Results revealed that V. anguillarum caused extensive histological damage to the gut but P. acidilactici did not. No signs of translocation of either the probiotic or pathogen were observed. Microbiological analyses indicated that P. acidilactici was able to outcompete V. anguillarum in the rainbow trout intestine and also to populate or colonise the mucosa. Additionally, elevated leucocyte levels and goblet cells in the epithelium of P. acidilactici fed fish, and intestines exposed to P. acidilactici, suggests that P. acidilactici might have potential use in controlling vibriosis. In vivo disease-challenge studies are warranted to ascertain if V. anguillarum infections can be controlled in rainbow trout using dietary applications of P. acidilactici.

Nursery Protocols for the Rearing of the Brown Shrimp, Farfantepenaeus aztecus: Effects of Stocking Density and Salinity

Abstract Recreational saltwater fishing in coastal areas of the United States of America is partly dependent on the availability of live bait for anglers. One bait species commonly used is the brown shrimp, Farfantepenaeus aztecus. Three experiments were conducted with eight-day-old post-larvae (PL8) to evaluate the effects of stocking density and water salinity on survival, growth, and feed conversion ratio (FCR) of F. aztecusin nurseries. In the first experiment, the effects of stocking density were evaluated for a period of 11 days. Post-larvae (PL) were stocked into round tanks (760 L) at densities of 30, 40, 50, and 60 PL/L with four replicates per treatment. There were no significant differences (P > 0.05) in final mean weight, survival, and estimated FCR among treatments. In the second experiment, shrimp were stocked into 159-L square polyethylene tanks at four densities (1.0, 1.9, 7.9, and 13 PL/L) and maintained for 12 days. Shrimp reared at low densities grew significantly larger and had significantly lower FCR than those stocked at higher densities. There were no significant differences in survival. In the third experiment, PL were stocked at two salinities (16 ppt and 32 ppt) with six replicates per salinity. Three of the tanks at each salinity were then treated with EDTA (3 ppm). Fourteen days after the start of the experiment, sub-samples of shrimp from each treatment were weighed and returned to the tanks. Salinity in the 32 ppt treatment was then gradually decreased to 16 ppt during a 24-hour period and the shrimp reared for an additional seven days. There were significant differences in mean weights among treatments at the end of the 14 day grow-out period (32 ppt, 10.1 mg; 16 ppt, 7.2 mg). At the end of the experiment, the use of EDTA did not seem to have an effect on production. However, shrimp subjected to late acclimation to the lower salinity were significantly smaller than those acclimated at stocking (11.8 mg vs. 21.2 mg). This reduced weight is presumably due to acclimation stress resulting in a lag in growth. The high salinity treatment resulted in significantly higher survival (32 ppt, 51.3%; 16 ppt, 44.4%), while the FCR was significantly lower (32 ppt, 1.75; 16 ppt, 2.08). Present results indicate that nursery systems, if properly utilized and correctly managed, could assist in the development of a viable bait-shrimp aquaculture industry.

Effect of Dietary Protein Level on Growth Performance and Blood Parameters of Marbled Spinefoot Siganus rivulatus

The present study evaluated the effect of dietary protein levels on growth performance and blood parameters of juvenile marbled spinefoot (Siganus rivulatus). Five semipurified, isoenergetic (14.2 MJ digestible energy/kg; 84 g lipids/kg) diets were formulated to contain 30, 35, 40, 45, and 50 g crude protein (CP)/100 g diet. Groups of 15 juvenile fish (7.4 g individual weight) were randomly assigned in triplicate to each of the five treatments and offered the test diets three times daily ad libitum for 9 weeks. Total erythrocyte and differential leukocyte counts, hematocrit, hemoglobin, blood glucose, protein, and serum aspartate aminotransferase and alanine aminotransferase were evaluated. Survival was greater than 95% in all treatments. Maximum growth was observed in fish offered the diet containing 40 g CP/100 g diet crude protein. Differences in dietary protein level had no effect on the hepatosomatic and viscerosomatic indices of the fish, but whole body composition was influenced by diet. Blood parameters showed no physiological or metabolic dysfunctions among fish offered any of the five diets. Findings of the present work strongly suggest that diets containing 40 g CP/100 g and 14.2 MJ digestible energy/kg are suitable for good growth of juvenile spinefoot rabbitfish Siganus rivulatus and do not affect hematological parameters.

Ensuring Food Security by Improving “Freshwater Use Efficiency” or by Farming the Seas

The present chapter discusses water use and food production in a freshwater challenged world with a growing human population. Proposed approaches to ensure food security are multifaceted but simple. First, we need to improve water use efficiency in all food production systems. Second, we need to develop technology to farm dry or semi-arid areas of the world. Third, we should integrate various fields of agriculture and animal husbandry to improve water productivity. Fourth, we should learn to go for proven local technologies rather than glamourous setups that do not work in rural settings. Fifth, we should seriously start working on farming the oceans. Last but not least, we need to invest in education and training. The common thread in all these suggestions is the use of aquaculture to improve food production efficiency. These proposals are not novel ideas but most governments have failed to implement even the simplest of suggestions. However, now that climate change adaptation plans are at the forefront of international discussions, maybe more countries will implement suggestions for water use efficiency improvement summarized in this chapter in order to better ensure sustainable food production.

Lignocellulose Improves Protein and Amino Acid Digestibility in Roosters and Egg Hatchability in Broiler Breeders

The present work assessed the effect of supplementation of 0.8% dietary Arbocel® RC Fine, a readily available commercial lignocellulose, to poultry feed. In a complete randomized design using 36 individually caged mature dubbed Hy-Line roosters (aged 55 weeks) grouped in 4 treatments with 9 birds per treatment, a digestibility trial was performed to determine apparent and true metabolizable energy values along with digestibility coefficients of protein and amino acid in Arbocel® containing diets. Results showed that 0.8% Arbocel® supplemented diets improved protein digestibility by 6% (P<0.05). Additionally, Arbocel® caused an increase in apparent and true amino acid digestibility in roosters when compared to control diets and controls with 0.8% wheat bran (WB) supplementation. In a second experiment, 26,000 layers and 2,600 roosters aged 33 weeks (Ross 308 broiler breeder strain) were maintained in 6 poultry houses at a commercial breeding farm, with an average of 4330 layers and 433 roosters per house. Performance, egg grade, and hatchability rate were assessed over a post peak period of 6 months. Compared to the control group fed the 0.8% WB diet, the 0.8% lignocellulose dietary supplementation resulted in a decrease (P<0.05) in percent infertility leading to an average increase of 4.07% (P<0.05) in egg hatchability. The Arbocel® fed group had 3.8 more eggs per housed hen compared to control birds. Overall, Arbocel® supplementation at 0.8% resulted in the production of 5.7 more saleable chicks per housed hen during the 6 months trial, a sizeable profit to the farmer.