Date: 16/08/2022
Animal health maintenance is a constant concern of professionals involved in zootechnical creation. With the development of agricultural sectors, the demand for greater productivity per area - and, therefore, the intensity and efficiency of this productive sector - has increased exponentially.
New technologies related to animal management, environment, genetic improvement and nutrition are being developed and used to make said productive increase possible. These changes in the agricultural routine and scenario, in turn, cause the animals to be exposed to stressful factors, such as intensive management practices and high cultivation/breeding densities that impact their life quality.
Stress puts the animals’ health at risk, increasing the possibility of pathogenic infections and other diseases that will impact on productive performance - making it smaller and increasing its mortality.
There are several pathogenic microorganisms in the aquatic environment that can cause pathologies and diseases in cultivated species. Among them is Vibriosis, a bacterial infection with potential to bring serious damage to producers, especially to marine shrimp ones, who are highly affected by this disease.
Most species of Vibrio bacteria are not capable of promoting serious problems and losses in aquaculture production. However, some of them can cause extensive damage, quickly wiping out entire flocks in a production system, especially when there is a conducive environment for it – that is, in animals that are stressed due to water quality issues or poor management.
In addition to the losses generated in the production of shrimp in captivity, some vibrio species are zoonotic agents. In other words, they are sources of food infections for humans when contaminated food is eaten raw or undercooked. Thus, it is extremely important for public health to prevent and treat outbreaks of vibriosis and mitigate the growth of Vibrio bacteria in animals cultivated for human consumption.
As with other pathologies, several paths can be taken to prevent the onset of these diseases and mitigate these problems when they occur. For this, it is important to understand more about the microorganisms that generate these pathologies in order to fight them.
Characteristics of bacteria of the genus Vibrio spp. and Vibriosis
They are normally found in cultured water, forming part of the natural microbiota of healthy cultured organisms - and become pathogenic when the body's natural defense mechanisms are suppressed. Bacteria can use skin (being wounds and lesions its main entrance), gills and the gastrointestinal tract as a route of entry into the animal.
Vibrios can cause five main types of disease in shrimp: tail necrosis, shell disease, red disease, loose shell syndrome and white intestine disease. They are mainly associated with the species Vibrio harveyi, Vibrio parahaemolyticus, Vibrio alginolyticus, Vibrio anguillarum, Vibrio vulnificus and Vibrio splendidus.
Vibriosis can occur in multiple ways (enteric, cuticular, hepatopancreatitis, muscle opacity and systemic forms), each caused by different types of stressors that will trigger a state of immunosuppression in cultivated animals. Among these stressors are low water quality, nutritional imbalance in the diet, high density, extreme changes in water temperature and other physical-chemical factors.
The disease often starts with external changes and, if left untreated, its infection can become systemic, leading to increased mortality.
In fish, as explained by this well-crafted review by researchers from Universiti Putra Malaysia, Vibriosis begins with dermal ulceration, followed by systemic infection and septicemia. It shows up among the most common diseases that lead to massive mortality of farmed shrimp, fish and shellfish. When affected, the animals present lethargy, anorexia, abnormal swimming, ulcerative and hemorrhagic skin lesions, abdominal distension, exophthalmos, branchial necrosis, darkened skin, all of which can lead to death.
When it comes to shrimp, as reviewed by Indian researchers in a study[1], vibriosis leads to wounds in several locations, such as the cuticle, pale muscle tissue, formation of nodules in the heart, gills, hepatopancreas, antennae, nerve cord and muscle, brown or black lesions on the cuticle, appendages or gills and tail necrosis. Post larvae affected by the disease may have brownish gills, hepatopancreas atrophy with multifocal necrosis and hemolytic inflammation, loss of midgut epithelium, among others.
The most common method of analyzing vibrio load is counting the number of colonies present in the water and in the animals themselves. To this end, plating is carried out in a selective culture medium for vibrios called TCBS - Thiosulphate-Citrate-Bile-Sucrose agar. It is a selective culture medium for bacteria of this genus, which normally form two different types of colonies, green and yellow. Vibrio isolates can be identified by several techniques, such as Gram stain, motility, oxidase test, growth in the presence of NaCl, mode of glucose utilization, nitrate reduction and luminescence. Other identification methods include biochemical or molecular laboratory tests through PCR (polymerase chain reaction).
Vibriosis prevention and control measures through nutrition
As with other diseases and pathological situations, constant monitoring and prevention are two of the most effective ways to prevent disease outbreaks and to lessen the damage of a pathogen when it manages to establish itself in a flock of animals.
Therefore, among several ways to carry out prevention, the maintenance of water quality; balanced diet; reduction of stress factors such as high stocking density and careless management; constant and routine monitoring of the production system; implementation of resistant strains; use of biosecurity and sanitation techniques for materials, equipment and tanks where the animals are housed should be mentioned as essential.
For a long time, the use of antibiotics was used extensively in aquaculture as a treatment for diseases infecting farmed animal lots. However, alternatives have been listed so that it is possible to renounce and even reduce the use of said medications in view of the negative implications (possible contamination of meat products with antibiotic residues, increase in bacterial resistance to antibiotics and consumer restriction).
Feed and food additives can stimulate the immune system of fish and shrimp and diets must be formulated not only with productive criteria, but also considering the ability of this diet to promote fish health.
Quality food - powered by a rich, balanced diet and the offer of fish formula made of quality ingredients - is one of the best ways to guarantee profitability to the producer. Animals fed with adequate diets will show adequate growth and excellent zootechnical indices, in addition to remaining healthy and being able to maintain their health even with the inherent stress of intensive animal production - the most used system in modern aquaculture.
In this scenario, some ingredients may be presented as alternatives, since they provide greater digestibility, nutritional balance and use of food - resulting in less degradation of the crop’s water quality.
The use of food and food additives (phytogenics, probiotics and functionals) that act on the immune system are currently among the main ways to maintain health of farmed fish and shrimp herds.
Maintaining intestinal integrity and the health of the intestinal microbiota is essential for the cultured animal to reach its full genetic potential for healthy growth and, consequently, becoming a product of nutritional and sanitary quality for human consumption.
Functionals – Hydrolyzed Proteins
Therefore, it is necessary to think of a food solution that can offer nutrient abundance also a sustainable alternative to the environment, especially related to the use of animal by-products. One of the solutions found is BRF Ingredients' Chicken Protein Hydrolysate, a functional protein specially formulated to improve animal health and performance.
To achieve high performance, CPH goes through the hydrolysis process. Even though it can be carried out with different techniques, BRF’s enzymatic formula is the most suitable one due to its simplicity and efficiency - with the fact that it doesn’t require rigorous chemical methods for its production being a bonus. Plus, the enzymatic hydrolysis process can generate smaller chains of amino acids, the bioactive peptides, which, by presenting specific functionalities that act directly on the animal organism, improves the survival rate of tilapia and shrimp.
In this way, CPH is an ingredient produced from the use of animal leftovers – chicken offal and viscera –, adding more value to the nutrient while making it more sustainable: it adds value to poultry by-products, reduces the amount of waste in the environment and the pollution in growing water.
It’s important to emphasize that the use of CPH on shrimp and tilapia diets, for example, decreased the animals’ mortality. According to research carried out by the Federal University of Santa Catarina (UFSC), it was shown that the inclusion of 1.5% of Chicken Protein Hydrolysate in shrimp feeding reduced the mortality of crustaceans challenged with the injection of a solution containing Vibrio parahaemolyticus after 24 hours of challenging.
Furthermore, it was observed that 48 hours after Vibrio injection, shrimp fed diets containing 1.5% and 6% of Protein Hydrolysate showed greater survival than those not supplemented with CPH. In this sense, it was also observed, in a study carried out in Can Tho, that the cumulative mortality of L. vannamei after 14 days post-infection with Vibrio parahaemolyticus decreased 50% with the inclusion of 5.12% of BRF Ingredients’ Chicken Protein Hydrolysate.
As for tilapia, a scientific test carried out by the State University of Western Paraná (UniOeste) showed that the inclusion of 2.5% of Chicken Protein Hydrolysate increased the survival rate in post-larvae phase by 12% compared to the controlled group.
In this way, the importance of food in preventing and controlling the involvement of animals by Vibrio and its initial stages is reinforced - increasing survival rate to later act on weight gain and greater yield of the filets.
Immunostimulants
Immunostimulants promote immune response and have been shown to be successful in reducing mortality associated with vibriosis. Research has shown that the use of bioflocs produced by biofloc culture system (BFT) and yeasts (Saccharomyces cerevisiae) can reduce the presence of Vibrio parahaemolyticus in the intestinal tract of shrimp, ensuring nutritional needs and providing a reduction in the risk of diseases by acting as a probiotic, in addition to preventing the release of bioflocs into the environment and minimizing ecosystem problems. This demonstrates that there was an immunostimulating effect by including autolyzed yeast in the shrimp diet.
Probiotics
These act through competitive exclusion - competing for nutrients, space and modulation of the immune system. It has been shown, for example, that probiotic strains such as Bacillus spp. can inhibit the growth of pathogenic bacteria of the genus Vibrio. This result demonstrates that the beneficial action of probiotics in the animal's digestive tract may provide an environment that will not promote the growth of pathogenic bacteria, such as those of the genus Vibrio.
Conclusion
Pathogenic microorganisms are often naturally present in the aquatic environment or even in the organism of the cultured animal and will only become a problem when the animal is susceptible - either due to excess stress inherent to the adverse situations of intensive rearing systems, or by poor nutrition - which will not provide healthy growth for the cultivated animal.
Thus, it’s essential that the choice of food to be offered to farm animals considers the needs of the aquatic organism being cultivated, since the aquatic environment is rich in microorganisms that can lead to diseases in the lots.
Both fish and shrimp are subject to being affected by some pathology and ensuring good nutrition for these animals is essential for successful breeding.
Choosing selected, balanced and digestible ingredients for diet formulation will provide the production of high-quality food envisioning the healthy growth of the cultivated animals. Thus, investing in adequate food will reduce the risks of diseases in animals, and ensure good zootechnical performance, producer profitability and product quality.
In this sense, Chicken Protein Hydrolysate presents itself as an excellent food source for aquatic organisms, as it has already demonstrated high digestibility and nutrient absorption capacity, in addition to the ability to act on survival rates in the early stages.
