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Emma Patrick Group

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Benjamin Taylor
Benjamin Taylor

Feed And Grow Fish Modl


Aquafeed companies aim to provide solutions to the various challenges related to nutrition and health in aquaculture. Solutions to promote feed efficiency and growth, as well as improving the fish health or protect the fish gut from inflammation may include dietary additives such as prebiotics and probiotics. The general assumption is that feed additives can alter the fish microbiota which, in turn, interacts with the host immune system. However, the exact mechanisms by which feed influences host-microbe-immune interactions in fish still remain largely unexplored. Zebrafish rapidly have become a well-recognized animal model to study host-microbe-immune interactions because of the diverse set of research tools available for these small cyprinids. Genome editing technologies can create specific gene-deficient zebrafish that may contribute to our understanding of immune functions. Zebrafish larvae are optically transparent, which allows for in vivo imaging of specific (immune) cell populations in whole transgenic organisms. Germ-free individuals can be reared to study host-microbe interactions. Altogether, these unique zebrafish features may help shed light on the mechanisms by which feed influences host-microbe-immune interactions and ultimately fish health. In this review, we first describe the anatomy and function of the zebrafish gut: the main surface where feed influences host-microbe-immune interactions. Then, we further describe what is currently known about the molecular pathways that underlie this interaction in the zebrafish gut. Finally, we summarize and critically review most of the recent research on prebiotics and probiotics in relation to alterations of zebrafish microbiota and immune responses. We discuss the advantages and disadvantages of the zebrafish as an animal model for other fish species to study feed effects on host-microbe-immune interactions.




Feed And Grow Fish Modl



Figure 2. Overview of the interaction of pre- and probiotics, immune system and microbiota in the zebrafish intestine. We summarized the interactions of microbiota and feed components, immune system and feed components and microbiota and immune system. We highlighted the questions that still remain unsolved in the field.


inSTREAM (the individual-based Stream TRout Environmental Assessment Model) is an individual-based model (IBM) of trout in a stream environment; it predicts how trout populations respond to many kinds of environmental and biological change. The simulated environment includes spatially and temporally varying in hydraulic conditions (depth, velocity, cover providing velocity shelter), temperature, turbidity, and food availability. The model trout adapt to changing conditions mainly by selecting which habitat to use, making a tradeoff between growth rate and mortality risk. Trout feed and grow, experience various kinds of mortality, and reproduce.


Bleach contains 90% of water. Mold loveswater. When bleach is applied, the chlorine quickly evaporates after useleaving behind a lot of water. This water often soaks into the porous surfaceallowing the mold to flourish and re-grow in the moist environment. Bleachfeeds the internal mold spores. Even though the surface may look bleached andclean, the remaining spores will root deeper, stronger and will often returnworse than before.


The approximate generation time for Danio rerio is three months. A male must be present for ovulation and spawning to occur. Zebrafish are asynchronous spawners[25] and under optimal conditions (such as food availability and favorable water parameters) can spawn successfully frequently, even on a daily basis.[26] Females are able to spawn at intervals of two to three days, laying hundreds of eggs in each clutch. Upon release, embryonic development begins; in absence of sperm, growth stops after the first few cell divisions. Fertilized eggs almost immediately become transparent, a characteristic that makes D. rerio a convenient research model species.[20] Sex determination of common laboratory strains was shown to be a complex genetic trait, rather than to follow a simple ZW or XY system.[27]


The zebrafish embryo develops rapidly, with precursors to all major organs appearing within 36 hours of fertilization. The embryo begins as a yolk with a single enormous cell on top (see image, 0 h panel), which divides into two (0.75 h panel) and continues dividing until there are thousands of small cells (3.25 h panel). The cells then migrate down the sides of the yolk (8 h panel) and begin forming a head and tail (16 h panel). The tail then grows and separates from the body (24 h panel). The yolk shrinks over time because the fish uses it for food as it matures during the first few days (72 h panel). After a few months, the adult fish reaches reproductive maturity (bottom panel).


Zebrafish have also been found to regenerate photoreceptor cells and retinal neurons following injury, which has been shown to be mediated by the dedifferentiation and proliferation of Müller glia.[54] Researchers frequently amputate the dorsal and ventral tail fins and analyze their regrowth to test for mutations. It has been found that histone demethylation occurs at the site of the amputation, switching the zebrafish's cells to an "active", regenerative, stem cell-like state.[55][56] In 2012, Australian scientists published a study revealing that zebrafish use a specialised protein, known as fibroblast growth factor, to ensure their spinal cords heal without glial scarring after injury.[4][57] In addition, hair cells of the posterior lateral line have also been found to regenerate following damage or developmental disruption.[50][58] Study of gene expression during regeneration has allowed for the identification of several important signaling pathways involved in the process, such as Wnt signaling and Fibroblast growth factor.[58][59]


In probing disorders of the nervous system, including neurodegenerative diseases, movement disorders, psychiatric disorders and deafness, researchers are using the zebrafish to understand how the genetic defects underlying these conditions cause functional abnormalities in the human brain, spinal cord and sensory organs.[60][61][62][63] Researchers have also studied the zebrafish to gain new insights into the complexities of human musculoskeletal diseases, such as muscular dystrophy.[64] Another focus of zebrafish research is to understand how a gene called Hedgehog, a biological signal that underlies a number of human cancers, controls cell growth.


Drug screens in zebrafish can be used to identify novel classes of compounds with biological effects, or to repurpose existing drugs for novel uses; an example of the latter would be a screen which found that a commonly used statin (rosuvastatin) can suppress the growth of prostate cancer.[101] To date, 65 small-molecule screens have been carried out and at least one has led to clinical trials.[102] Within these screens, many technical challenges remain to be resolved, including differing rates of drug absorption resulting in levels of internal exposure that cannot be extrapolated from the water concentration, and high levels of natural variation between individual animals.[102]


Zebrafish have been used as a model system to study obesity, with research into both genetic obesity and over-nutrition induced obesity. Obese zebrafish, similar to obese mammals, show dysregulation of lipid controlling metabolic pathways, which leads to weight gain without normal lipid metabolism.[142] Also like mammals, zebrafish store excess lipids in visceral, intramuscular, and subcutaneous adipose deposits. These reasons and others make zebrafish good models for studying obesity in humans and other species. Genetic obesity is usually studied in transgenic or mutated zebrafish with obesogenic genes. As an example, transgenic zebrafish with overexpressed AgRP, an endogenous melacortin antagonist, showed increased body weight and adipose deposition during growth.[142] Though zebrafish genes may not be the exact same as human genes, these tests could provide important insight into possible genetic causes and treatments for human genetic obesity.[142] Diet-induced obesity zebrafish models are useful, as diet can be modified from a very early age. High fat diets and general overfeeding diets both show rapid increases in adipose deposition, increased BMI, hepatosteatosis, and hypertriglyceridemia.[142] However, the normal fat, overfed specimens are still metabolically healthy, while high-fat diet specimens are not.[142] Understanding differences between types of feeding-induced obesity could prove useful in human treatment of obesity and related health conditions.[142]


Schooling Fish - These fish swim together in small schools. They are startled by the presence of movement. Aquatic and Semi-Aquatic animals have a lower chance of disturbing them and thus, have an easier time getting within striking range. These are the fish Juvenile (0-50% growth)/Low scale animals will primarily feed on. Attack into the school of fish in order to catch one. There is a percentage chance. The more suited the animal is for fishing, the higher the chance.


Elite Fish - These fish are large and do not school. They require pursuit to catch and are a prize for any creature capable of tackling them. These are the fish Adult (50-100% growth)/Large scale animals will feed on. Smaller creatures do not stand much chance of catching these behemoths."


Most fish breeding programs aim at improving growth rate and include feed conversion ratio (FCR) neither in the breeding goal nor in the selection index, although decreasing FCR is known to increase farm profit and decrease environmental impacts. This is because FCR is difficult to measure in fish that live in groups and FCR is assumed to have a favourable (negative) genetic correlation with growth, although the magnitude of this correlation is unknown. We investigated the effect of the genetic correlation between growth and FCR on the economic and environmental responses of a two-trait breeding goal (growth and FCR), compared to a single-trait breeding goal (growth only). Next, we evaluated the weights to assign to growth and FCR in a two-trait breeding goal to maximize sustainability of fish production.


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