For a few years, we have been receiving advice from international health organisations about the use of antibiotics in the animal production industry. The World Health Organization (WHO) warned that a lack of effective antibiotics was as serious a threat to security as a deadly disease outbreak. We should focus our attention on a set of measures which promote safe animal growth and mainly act in the prevention of diseases.
The role of intestinal microbiota
Many studies prove that beyond antibiotics’ immediate impact on microbiota, these types of medicines also affect the genetic expression, protein activity, and general metabolism of intestinal microbiota. As well as increasing the immediate risk of infection, the microbial changes caused also have long terms effects on the basic immune system.
Animals’ intestinal microbiota plays an important role in regulating their immune systems, since it not only modulates various physiological, nutritional, metabolic and disease-fighting processes, but can also alter the physiopathology of illnesses, conferring resistance, or promote enteric parasitical infections. Natural intestinal bacteria act as molecular adjuvants which provide indirect immunostimulation, helping the organism defend itself against infections.
Immune system – first line of defence
Broilers have a large quantity of lymphoid tissue and immune system cells in their intestinal mucosa, called the GALT (gut-associated lymphoid tissue), which in turn constitutes the MALT (mucosa-associated lymphoid tissue). The GALT is constantly exposed to food antigens, microbiota, and pathogens, and needs to identify components which are present in the intestinal lumen and which could present a possible threat to the animal. The immune system’s first line of defence is composed of phagocytic cells (macrophages, heterophiles, dendritic cells and natural killer cells), which have Toll-type receptors on their surface. These receptors recognise microbial standards and induce an immediate innate immune response. After this activation and phagocytosis, the phagocyte (antigen-presenting cell – “APC”) presents a processed fragment of the antigen and a chain reaction is initiated against it. The innate immune system’s recognition of pathogens first triggers immediate innate defences and, subsequently, the activation of the adaptive immune response.
It is important to emphasise that this series of responses of the innate immune system requires several nutrients, especially metabolic energy, since it is a nonspecific and pro-inflammatory response, but necessary to control the proliferation, invasion, and damage caused by the antigen in the animal organism. However, a prolonged pro-inflammatory response may lead to secondary diseases, immunosuppression, maintenance of immune homeostasis, intestinal dysbiosis, and finally, decline in performance and mortality.
Decreasing the occurrence of immunosuppression
A correct program of measures, including balanced nutrition, vaccination, reduction of stress factors, good management and animal well-being practices, can considerably decrease the occurrence of immunosuppression. Adding dietary additives, which act in the modulation of the innate immune system and microbiota, improves the defence response against potential challenges.
The yeast cell wall Saccharomyces cerevisiae (ImmunoWall, ICC Brazil) is derived from the process of sugar cane fermentation in ethanol production, and is made up of around 35% β-glucans (1,3 and 1,6) and 20% Mannan-Oligosaccharides (MOS). β-glucans are recognised for their phagocytic cells, encouraging them to produce cytokines which will initiate a chain reaction to induce immunomodulation and enhance the responsiveness of the innate immune system. On the other hand, MOS are able to agglutinate type-1 fimbriae pathogens and various strains of Salmonella and Escherichia coli.
Improved intestinal integrity
A recent study conducted by Beir?o et al. (2018), in which broilers received ImmunoWall supplements (0.5 kg/MT) and were infected with Salmonella Enteritidis [SE] (via an oral dosage of 108 CFU per broiler) at two days of age, showed that from four to eight days of age (two and six days post-infection, respectively), the yeast cell wall product reduced the passage of the marker (Dextran-FITC, 3-5 kD) into the challenged broilers’ blood stream. These results show a significant improvement in intestinal integrity and permeability, since SE is a bacterium capable of sticking to the mucosa through its fimbriae, producing toxins and causing damage to tight junctions and enterocytes, invading them and translocating them into the blood stream and other internal organs and tissues .