The intestinal tract is home to trillions of bacteria, yeast and microorganisms comprising hundreds of beneficial species. these "friendly" microorganisms are called probiotics, meaning "for life". They are an essential link in proper health and well-being.

It is important to keep friendly flora in balance and in plentiful supply. Without sufficient numbers of viable, friendly bacteria, our intestinal terrain in thrown off balance, resulting in a wide range of possible health problems and disease conditions.

Diarrhoea due to enteritis and gastroenteritis flushes intestinal microorganisms out of the gastrointestinal tract, leaving the body vulnerable to opportunistic infections. Probiotics can be used to replenish these protective bacteria and reduce the incidence of diarrhoea.

While antibiotics are very often effective at killing the offending bacteria they were prescribed to kill, antibiotics also kill many strains of protective bacteria. After treatment with antibiotics animals become more susceptible to colonization and infection by harmful gut bacteria, causing antibiotic associated diarrhoea. Probiotics in combination with and following antibiotic therapy can facilitate regrowth of a healthy microbial population and reduce the incidence of abdominal cramps and diarrhoea.

Probiotics can be used in situations where in intestinal microflora balance has been disturbed and related digestive tract dysfunction occurs.

Many strains of bacteria have been used in probiotic supplements. The most common strains are Lactobacillus acidophilus. Lactobacillus casei, Lactobacillus sporogens, Bifidobacterium bifidum, Bifidobacterium longum, Bacillus subtilis and the yeast Saccharomyces cereviasiae.

The observed benefits of probiotics may result from:

01. Defence against pathogens
02. Improving digestion
03. Boosting immunity
04. Synthesis of vitamins etc.

Defence Against pathogens

Some disease-causing bacteria can reduce animal's ability to absorb nutrients by disrupting the lining of the intestine. Friendly bacteria attach themselves to the intestinal wall and prevent the harmful strains such as E.coli, Bacteroides, Salmonella, Staphylococcus etc. from growing to a population where they can cause disease. They do this by producing lactic acid, hydrogen peroxide and other by products that make the environment hostile for undesired organisms.

They also compete with harmful bacteria for nutrients needed for growth, and by bacteriocin production, which is the production of compounds that have a lethal effect on harmful bacteria.

Improving Digestion

Certain strains of Lactobacilli, such as sporogens & acidophilus produce large amounts of proteases and peptidases that help digest proteins and also produce large amounts of lactase and similar disaccharidases that digest lactose and other simple sugars.

They are also involved in the production of several "gut nutrients", such as short-chain fatty acids, and the aminoacids arginine, cysteine and glutamine.

In addition, the attachment of the benefical bacteria may increase the absorptive surface area of the small intestine and enhance enzyme activity for greater nutrient absorption by the animal.

Boosting Immunity

The gastrointestinal system functions as one of the first lines of defense against foreign invaders. The microbes inhabiting the gastrointestinal tract and their activity have a major impact on the functioning of the intestinal immune system.

Beneficial lactic acid-producing bacteriae, such as Lactobacilli and Bifidobacteriae are capable of modulating the immune response in the surface of the gastrointestinal system. Their presence in the intestines is recognized and detected by immune system. This leads to immune activation with an increased prodution of white blood cells. To avoid this recognition from leading to an inflammatory response, which could lead to their own eradication or damage to the surface of the intestine, such lactic acid-producing bacteriae make immune cells in the surface of the gastrointestinal system produce anti-inflammatory compounds such as interleukin-10(IL-10). This does not weaken the immune system, but actually strengthens it, as has produced more white blood cells when it recognizes the lactic acid-producing bacteriae. These white blood cells are then available to deal with other unwanted microbes and other foreign substances at very short notice.

Synthesis

Probiotics can even synthesis and secrete vitamins like Vitamin K and B vitamins such as folic acid, niacin, riboflavin, B₁₂, B₆ and pantothenic acid, which are biocatalysts in food metabolism and help fight stress.

Overall effect and functions

Probiotics in Puppies

Puppies are born with bacteria-free digestive tracts, which are quickly populated by disease-causing and health-promoting bacteria. The question becomes, "Which type of bacteria will dominate?" Providing probiotic cultures shortly after birth can favor the beneficial bacteria. The lactic acid-producing bacteria could inhibit diarrhea-causing microorganisms, and can aid the puppy in the absorption of nutrients.

Diet changes and other challenges at weaning can alter a puppy's nutrient intake and health status. Controlling harmful bacteria in the digestive tract during variable food intake is very important. Probiotics can be mixed with the dry or moist food for daily maintenance.

Probiotics in Growing and Mature Dogs

Breeding, whelping, showing and heavy training can alter food intake and increase a dog's susceptibility to disease-causing organisms. Restoring nutrient intake, stabilizing the balance of digestive tract bacteria and proper immune function become critical during these challenging periods. Probiotics can play a major role during these critical periods. In addition, improving the nutritional status of the dog enhances the hair coat and energy level.