Probiotics have become increasingly popular in both the human and animal health supplement industries. What
exactly is a probiotic? The currently accepted Food and Agriculture Organization/World Health Organization definition of a probiotic is "live microorganisms which when administered in adequate amounts
confer a health benefit on the host." For many years, "beneficial bacteria" products have been available labeled as nutritional supplements. The big differences between a nutritional supplement and a probiotic is that the bacteria in the nutritional supplement doesn't have to be alive and there is no implied claim it will have any health benefits.
Until recently the Food and Drug Administration required products labeled as probiotics to be FDA approved or indexed because the definition (and public perception) of a probiotic meets the FDA's definition of a drug: "articles intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease" and "articles (other than food) intended to affect the structure or any function of the body of man or other animals" (Food, Drug, & Cosmetic Act, section 201 (g)(l). Now the FDA has relaxed its regulations on probiotics, allowing them to be labeled as probiotics with approval only necessary if any efficacy claims are made on the label. Now that FDA has changed its regulations, many products labeled as avian probiotics are being put on the market. It's important to know more about avian probiotics to wisely choose among these new products.
Avian Normal Bacteria
Back in the 1950s researchers determined that various species of Lactobacilli and anaerobic coccoid bacteria were the main normal bacteria in chickens and turkeys. In the late 1970's researchers began investigating the normal bacterial flora of pet birds. Most papers reported predominantly gram positive bacterial flora, and, as in poultry, most frequently various species of Lactobacilli and gram positive cocci. Gram negative bacteria were determined to be abnormal and potentially harmful to pet birds. One study examined the numbers of different bacteria in various healthy pet birds of different ages. They found that young birds had the highest numbers of normal bacteria and as birds aged they had fewer and fewer normal bacteria. At the same time, younger birds had fewer gram negative bacteria and older birds had more.
Other factors besides age can affect a bird's normal bacterial flora. Stress has been found to decrease numbers of normal bacteria in humans, animals, and poultry. The same research has not yet been done in pet birds, but they have systems similar to poultry so we would expect that they respond much the same way to stress. Antibiotic treatment not only gets rid of abnormal or pathogenic bacteria but normal bacteria as well. That's why you'll hear of birds getting yeast infections in their intestinal tract after treatment with tetracyclines. The yeast isn't being held in check by normal bacteria anymore.
Parent birds dose their chicks with their normal bacteria when they feed them. If the parents are older, have been stressed, or have been treated with antibiotics they may not have the normal bacteria they need to pass on to their chicks. Handfed chicks don't get their parents' normal bacteria. This can be one reason why handfed chicks have more problems with gram negative bacterial infections and yeast infections than parent raised chicks do.
A good probiotic helps a bird by becoming its normal bacterial flora and supporting the growth of other normal bacteria. When it does this it strengthens all the natural defenses a normal bacterial flora provides.
Desirable Characteristics of an Avian Probiotic
Most of the research in avian probiotics has been done in poultry. Only a few studies have used pet bird species. The following information, therefore, comes primarily from poultry. The pet bird information is included where appropriate.
After decades of research, the following list of characteristics of an ideal avian probiotic has been proposed:
• Ability to adhere to intestinal lining cells
• Species specific
• Ability to colonize and reproduce in the bird
• Ability to survive throughout the GI tract
• Produce materials that harm pathogenic bacteria
• Ability to improve immunity
• Safe-doesn't cause illness
• Survive processing and storage
ABILITY TO ADHERE: Adherence means that the bacteria attaches itself to the intestinal lining cells. Even if the intestine is rinsed off well the bacteria stay attached. Researchers became aware of the importance of adherence through a series of papers published in the 1970s by a man named Fuller. All the avian species he examined-chickens, turkeys, quail, ducks, pheasants, and pigeons-had Lac to bacillus species which adhered to crop cells. Lactobacillus species isolated from ten different mammalian species did not. Also, the other bacteria he isolated from birds did not adhere to cells, only Lactobacillus species did. Giving Lactobacilli from mammals to chickens had no effect, but giving adherent Lactobacilli from chickens resulted in better growth rates and resistance to gram negative bacterial infections. Since the discovery of adherence in avian lactobacilli, researchers continued to find that mammalian Lactobacilli have no effect in birds and avian strains of Lactobacilli with a high level of adherence provide the most health benefits. In psittacines, cockatiel chicks were given a Lactobacillus species found adhered to crop cells from healthy adult cockatiels, The group not given the adherent Lactobacilli developed a population of non-adherent Lactobacilli by two weeks of age(presumed to be from the environment). The groups given the adherent Lactobacilli had significantly faster growth rates, 100 times fewer gram negative bacteria, and higher total numbers of lactobacilli. So the non-adherent Lactobacilli didn't provide the benefits seen with an adherent Lactobacilli.
Researchers believe that birds need adherent bacteria so that when the crop empties there are still bacteria available to inoculate new food entering the crop and to provide a constant supply of bacteria for the entire intestinal tract. Adherent bacteria help prevent pathogenic bacterial infections by competing for binding sites. The pathogenic bacteria need to attach to the intestines before they invade or just to keep from being swept away by the movement of the intestinal contents. If all the binding sites are already occupied, they can't do as much damage. Research has also shown that when a Lactobacillus attaches itself to an intestinal lining cell, it triggers changes in the cells themselves that improves immunity, improves digestion and absorption of nutrients, and helps keep pathogenic bacteria from attaching.