Feeding Beneficial Bacteria: Probiotics

Pashu Sandesh, 27th June 2019

Poonam Shakya1, Anju Nayak2, Joycee Jogi3, Ajay Rai4 and Smita Bordoloi 5

Probiotics are live microbes which beneficially affect the host by improving its intestinal microbial balance. For many decades antibiotics have been used as feed additives in various species of animals, as to reduce the frequency of various diseases. Due to the emergence of antibiotic resistance, “Probiotics” as an alternative to antibiotics came in the scenario. The concept of probiotics goes back to Elie Metchnikoff who proposed that bacteria in fermented milk products may be capable to control bacterial fermentation in the intestinal tract of men and thus are health promoting. Today, yoghurts containing living probiotic bacteria are available for the consumer. 

Types of Probiotics

Many types of bacteria are classified as probiotics. The most commonly used bacterial probiotics are the strains of Bifidobacterium, Enterococcus, Lactobacillus, Bacillus, Pediococcus and Streptococcus. Some products contain viable yeast and other fungi in addition to bacteria. Administration of probiotic strains significantly improves feed intake, feed conversion efficiency, daily weight gain and total body weight in chicken, pig, sheep, goat, cattle and equine.

Composition of Probiotics

 Probiotics can be presented to the animal in various ways. They can either be included in the pelleted feed or produced in the form of capsules, paste, powder or granules which can be used for dosing animals directly or through their food. Nowadays, multiple- strain preparations are used which are active against a wider range of conditions and animal species.

Modes of Action

The mechanisms by which probiotics elicit their beneficial effects on the host can vary widely. Some effects result from direct interactions with the host epithelial and immune system, whereas others mediate their effects via modulation of resident intestinal flora and prevention of pathogen establishment.

  1. Chemical Inhibition- The production of antagonistic chemicals such as organic acids, small inhibitory chemicals, hydrogen peroxide and antimicrobial peptides (bacteriocins) by intestinal organisms have been implicated in the control of intestinal populations. These chemicals can kill pathogens directly or can generate localized “microenvironments” unfavourable for pathogen establishment.
  2. Competitive Exclusion- This refers to the process in which epithelial associated or bound microorganisms inhibit contact between pathogens and host epithelial cells.
  3. Microbially mediated immune development- Intestinal bacteria have a profound effect on the immune development of the gastrointestinal system and are a major source of antigenic material that stimulates the development of gut-associated lymphoid tissue and Peyer’s patches, the production of antimicrobial peptides and the production of protective IgA molecules.

Characteristics of a Good Probiotic

  1. It should be a strain which is capable of exerting a beneficial effect on the host animal. Eg; Increase growth or resistance to disease.
  2. It should be non- pathogenic. 
  3. It should be present as viable cells, preferably in large numbers.
  4. It should be capable of surviving and metabolizing in the gut. Eg: in low pH and in the presence of organic acids.
  5. It should be stable and capable of remaining viable for long periods under storage and field conditions.
  6. It must remain alive during the technological processes during fodder production.
  7. It should be free of significant adverse side effects on targeted species.
  8. It should be genetically stable.

Application in Animal Production

  1. Growth- Administration of probiotics in feed significantly improves the feed intake, feed conversion ratio, daily weight gain and total body weight in pig, chicken, sheep, goat, cattle and equines. Probiotic reduces leg weakness in broilers and prevented starvation sterility of young sows.
  2. Meat Production- Probiotics increase the carcass output and water holding capacity and decreases the meat hardness. Probiotics have been found to reduce mortality and morbidity of growing rabbits during the fattening periods. Several probiotics are used for fermented sausages such as lactic acid producing bacteria, mainly Lactobacillus, Pediococcus and Streptococcus.
  3. Milk Production- The supplementation of animal feed with probiotics has a beneficial effect on milk yield, fat and protein content. Supplementation of Saccharomyces cerevisiae increases milk yield in dairy cows which is mainly due to the increase in the number of cellulolytic bacteria, fibre degradation and changes in volatile fatty acid of the rumen.
  4. Egg Production- Probiotic supplementation in feed increases egg quality and egg production, reduces triglycerides and plasma cholesterol and decreases egg contamination. It also increases eggshell weight, shell thickness and serum calcium.


The development of probiotics for farm animals is based on the knowledge that intestinal microflora is involved in disease resistance. The stressful conditions experienced by the young animal causes changes in the gut microflora which can be repaired by probiotic supplementation. The probiotic therapy provides the type of microflora which exists in wild animals uninfluenced by modern farm rearing methods. Thus, combating the problem of disease resistance.

Poonam Shakya1, Anju Nayak2, Joycee Jogi3, Ajay Rai4 and Smita Bordoloi 5

1,3,4 Assistant Professor

2 Associate Professor & In Charge Head

5 PhD Scholar

Department of Veterinary Microbiology, Veterinary College, NDVSU, Jabalpur (M.P.)