In recent years, increasing concern about the continuous and long-term use of antibiotics and other growth stimulants and their harmful effects has prompted experts to start using and evaluating probiotics. These microorganisms are living microbial compounds that are directly added to the feed of livestock and poultry and have a very favorable effect on their performance, growth and health. Probiotics not only do not cause disease, but also prevent the proliferation and growth of pathogenic bacteria in the digestive system of animals and increase the beneficial microflora in the digestive system of livestock and poultry, thereby eliminating the need for antibiotics. do Those that have been used as probiotics include bacteria and fungi such as Lactobacillus, Bifidobacterium, Aspergillus oryzae and Saccharomyces cerevisiae. In fact, in addition to affecting the immune system, they also improve rumen fermentation. One of the problems in the development and scientific development of probiotics is little knowledge about the complexities of the gastrointestinal-intestinal environment and the inability to identify thousands of potential species that are effective in the microecology of this tract.
Probiotic means “for life” and is the opposite of antibiotic “against life”. Probiotics are selected microbes that are used to replace the digestive tract of humans or animals. The purpose of this replacement is to improve the physiological conditions and generally change the complex ecosystem of the intestine. In normal conditions, there are approximately 1014 or 100,000 times more than the number of people in the world and more than 400 different types of microorganisms in the human digestive tract. When a person or an animal is born, his digestive system does not contain any type of micro-organism. After birth, the replacement of microbes begins and microbes enter the digestive system from the environment and form a colony. These microbes are affected by the food eaten and the conditions of the intestinal environment. After a certain period of time, the microbes of the digestive system are stabilized due to the constant conditions of the environment and the combination of nutrients and existing physiology, which is necessary to maintain life. , vitamins, and bacteriocins and as a result competitive removal and decomposition of active compounds such as steroid hormones and stimulate the body’s immune system.
Mechanisms of action of probiotics:
1- Connecting to the wall of the digestive system and preventing the formation of a colony by pathogenic microorganisms
2- Neutralization of toxins produced in the digestive system (by pathogens)
3- They have bactericidal activity. Lactobacillus ferments lactose into lactic acid, thus destroying harmful bacteria by lowering the pH.
4- Improving the immunity level of the host body
Factors that change the microbial balance in the animal body
Transportation, temperature change, type of food, diseases, and antibiotics are the main factors that change the balance of microbes in the digestive tract. When the microbial balance is disrupted, the possibility of colony formation by pathogenic bacteria in the intestine increases. Changing the food is one of the factors that change the environment of microorganisms, and during the time when these microorganisms get used to the new environment, their number will be lower than normal, and this means creating space for pathogenic bacteria and the production of toxins by them, which ultimately causes Diarrhea or death of the animal. Colony formation in the intestine can occur at different levels. Microbes can attach to the surface of the intestinal epithelial cells or start forming colonies in the crypts.
The most important effects of probiotics in the production of animal and poultry feed factories
The effect of probiotics on performance is caused by the interaction of enzymes and metabolites produced by them and competitive elimination or stimulation of the body’s immune system. Probiotics produced based on spore bacilli are a type of probiotics used in animal and poultry feed factories. These products have many advantages, the most important of which is maintaining quality during the pelleting process.
In recent years, increasing concern about the use of antibiotics and other growth stimulants and their harmful effects has prompted experts to turn to the use and evaluation of probiotics. The main purpose of using probiotics in the nutrition of monogastrics is to fight against pathogenic microorganisms through competition and return the normal state of the intestinal microbial population to its original state, but in ruminants, the main purpose is to improve fermentation in the rumen. And the microbial strains used in monogastric and ruminant probiotics are different. These additives are generally consumed by animals in various forms such as flour, paste, capsule or liquid, but they should be used very carefully because factors such as the amount of chlorine in the water, the temperature of the water, the amount of mineral salts in the water and Feed, the presence of antibiotics and some drugs in feed and other factors affect the vital ability of these microbes.
The effect of using probiotics on the performance of the laying flock:
1- Increasing production
2- Reducing egg damage
3- Reduction of blood serum and yolk cholesterol
4- Improving food conversion rate
The digestive system of ruminants contains a powerful set of microorganisms that are responsible for digesting, absorbing and processing food.
Industrial production conditions of ruminants such as high density, production and feeding stresses, management challenges and epidemics of infectious diseases weaken the immune system and disrupt the microbial balance of the digestive system, resulting in the growth and production of harmful microorganisms and the production of harmful toxins and metabolites. As a result of such changes, there is a decrease in yield and an increase in losses in industrial farms.
The effect of using probiotics on the performance of ruminants (cows, sheep, goats, sheep, rams, etc):
1- Improving digestion and absorption of food, helping to break down cellulose
2- Production of essential enzymes such as cellulase, phytase, lipase, protease, etc.
3- Appetite stimulation
4- Production of vitamins, short chain fatty acids, fatty acids and…
5- Increase and regeneration of intestinal microvilli
6- Neutralizing the effects of toxins in the digestive system and feed
7- Dealing with pathogenic microorganisms in the digestive system (Salmonella, E. coli, Clostridia, protozoa, etc).
8- Stabilizing the natural flora of the rumen and intestine
9- stimulating and strengthening the immune system
10- Cholesterol reduction
Use of bacterial probiotics in calves
To date, the effectiveness of bacterial probiotics on dairy calves has been extensively investigated. Species such as lactobacilli, enterococci, streptococcus and bifidobacteria are used as probiotics in feeding young calves. In general, the importance of feeding probiotic bacteria (Lactobacillus species) in stressed calves is more related to the stability and maintenance of intestinal microbes than as a stimulus in production responses such as weight gain.
The main purpose of feeding these probiotics to calves is to quickly accustom them to solid feed by accelerating rumen and intestinal microbial stability and preventing the establishment of internal pathogens (which often lead to diarrhea).
In newborn calves, especially in stressful conditions, the microbial population is in a transitional and very sensitive state; So that sudden changes in diet or environment can cause changes in the microbial population of the digestive system.
Feeding calves with culture medium of lactobacillus and streptococcus species has reduced the incidence of diarrhea. In an experiment, it was shown that calves fed with Lactobacillus acidophilus compared to the control had a lower incidence of diarrhea in weeks 5, 7 and 8, which confirms the beneficial effect of lactobacilli in reducing the incidence of diarrhea.
The decrease in the occurrence of diarrhea may be related to the constant increase in the excretion of Lactobacillus and the unstable decrease in the total excretion of forms in the feces compared to feeding this type of additives, previous studies showed that animals that have a normal state of feces, have a lower tendency in total shedding. have forms in feces. The total shedding of forms in feces does not increase in calves that do not suffer from diarrhea. The rapid adaptation of calves to solid feed also depends on the development of the rumen epithelium and its capacity.
The effect of probiotics on growth performance
The use of probiotics as an additive improves the performance and well-being of the animal through the adjustment of the microbial population and homeostasis of the body. The use of probiotics in the diet in the form of single and multiple strains has a positive effect on the growth rate and productive performance of the animal. Oral inoculation of probiotics in cattle, sheep and goats leads to an increase in body weight and feed consumption in these animals. Live yeast probiotic improves feed consumption, feed efficiency, average daily weight gain, efficiency and milk quality in dairy cows.
Improving feed intake and digestibility of nutrients
The food resources available in tropical regions have low digestibility, which has decreased in these animals due to the imbalance in nutrients such as protein and the reduction in the speed of feed passing through the rumen. Therefore, supplementing low-quality forage with an additive helps the animal’s performance. Supplementing feeds with probiotics (yeast) reduces the interval between feedings in dairy cows, which helps stabilize rumen pH and thus stimulates forage consumption and increases the rate of fiber digestibility in the rumen.
Increasing feed conversion rate and growth rate
As an alternative to antibiotics, probiotics increase live body weight in ruminants by increasing feed intake, improving nitrogen efficiency and reducing nutrient excretion.
Effects of probiotics on milk
Probiotic consumption as an oral supplement for ruminants has beneficial effects on milk production, milk quality, and its functional compounds such as protein and fat content. The positive effects of probiotics on milk production and quality can be attributed to the positive effect of probiotics on the number of fiber-degrading bacteria and changes in the production of volatile fatty acids.
The effect of probiotics on the reduction of methane gas
Methane formation in the rumen is one of the important sources of greenhouse gas formation. Regardless of the species of ruminants, methane is one of the major sources of greenhouse gas pollution in ruminant production, accounting for 4% of 90% of greenhouse gases. Methane emitted from ruminants is one of the largest greenhouse gases, contributing about 25 times more to global warming than carbon dioxide. One of the useful strategies to reduce methane production in the rumen is manipulating biochemical pathways and reducing methane production in the rumen. Consumption of probiotics as an option to change rumen bacterial function is one of these methods.
The effect of probiotics on the immune system
The positive effects of probiotics on the immune system can be attributed to the ability of probiotics to stimulate and modulate the immune system, increasing innate and acquired immune responses.