DVM, PhD, Dipl. ACPV
Professor and Extension Poultry Veterinarian
Ohio State University Extension, Veterinary Medicine
Department of Veterinary Preventive Medicine
The Ohio State University
Columbus, Ohio, U.S.A.
As poultry health professionals, we have been primarily concerned with keeping our flocks healthy. However, the public's concern with such topics as food safety and antimicrobial resistance also impacts flock production.
Much of the public's concern regarding food safety revolves around such food-borne pathogens as Salmonella species and Campylobacter jejuni. Salmonella species of concern for the turkey industry include Salmonella typhimurium.
It has been demonstrated that carcass contamination can be directly related to intestinal colonization. Hence, for those of us working in production, we have been interested in reducing intestinal colonization of these bacteria through various methods.
Reduction of these food-borne pathogens, like Salmonella, requires good management practices. For example, an effective rodent control program is essential to any health management program. Rodents have been known to harbor Salmonella in their intestinal tract and they can serve as reservoirs of Salmonella on the farm. Rodents can shed Salmonella in their droppings and this can contaminate the turkey growing environment.
Although good management practices can reduce such pathogens like Salmonella on the farm, there are other methods that have been employed to try to alter intestinal colonization.
We will explore the use of probiotics and other alternatives to antibiotics as additional methods to reduce pathogen colonization in the intestinal tract.
What is intestinal colonization?
In any intestinal tract, bacteria can be found adhered to the surface or free in the lumen of the intestines. A newly hatched turkey poult is hatched with an intestinal tract that is free of bacteria. The intestines subsequently become colonized with the types of bacteria that the poult comes into contact with through exposure with the environment.
One of the first exposures of bacteria for the poult is in the hatcher. Previous research in our laboratory had demonstrated that the aerosolized bacteria increase significantly during the hatching process. Bacteria that were present on the eggshell surface can become aerosolized and subsequently ingested/inhaled by the turkey poult during hatching.
Another source of bacteria for poultry is the water and feed at placement. Hence, ensuring that these sources are clean will affect colonization.
There is a natural succession of microbial flora that is seen in the turkey poult intestinal tract. Our previous field and laboratory studies have demonstrated that gram-positive bacteria are predominant during the first two weeks of life in the jejunum portion of the intestinal tract, but at approximately 2.5-3 weeks of age, a consistent bacterial population is established.
Establishment of an intestinal flora is important for intestinal health. Such "good" bacteria like Lactobacillus colonize the intestines to prevent "bad" diseasing-causing bacteria from adhering to the intestines. In a simplified explanation of intestinal colonization, think of the intestines as a bus and the seats on a bus are where bacteria can attach to the intestines. If all the seats (or "spaces") are occupied by "good" bacteria, there are no empty seats for "bad" bacteria to get a space.
Establishment or adherence to the intestinal wall via colonization is how "bad" bacteria can gain a foothold in the intestines and cause intestinal disease.
Examples of "bad" bacteria include such organisms as Salmonella.
Hence, the faster one can establish "good" bacteria in the intestines, the lower the chance there is for bacteria to gain a foothold and cause disease.
This is one of the proposed advantages of administering probiotics in the intestinal tract. This is one way to provide intestinal flora to the young turkey poult. Hence, administration of probiotics at day-of-age has been proposed to establish an intestinal flora in the poult's intestines as soon as possible.
What are probiotics?
Probiotics are one type of commercially-available products that are available that contain live lactic-acid producing bacteria. Common lactic acid-producing bacteria include Lactobacillus species and Streptococcus species.
Probiotics can be administered alone via the water or incorporated in the feed. The purpose of administering probiotics is to establish a protective intestinal flora before disease-causing bacteria can gain a foothold and colonize the intestines. Lactic acid production inhibits some bacteria from proliferating in the intestines.
What conditions affect intestinal colonization?
In turkey production, any condition that can result in stress, ie overcrowding, transportation, vaccination, chilling and/or overheating, can create an imbalance in the intestinal microflora and may lead to a lower immune system. A lower immune system can lead to an increased susceptibility to disease.
It is during these periods of stress that products like probiotics may be useful.
How do probiotics work?
There are three primary ways in which probiotics work. They are:
- By maintaining a beneficial microbial population in the intestinal tract;
- By improving feed intake and digestion; and
- By altering bacterial metabolism.
What is the difference between probiotics and direct-fed microbials?
In 1989, the Food and Drug Administration required manufacturers to use the term "direct-fed microbials" instead of the term probiotics. However, direct-fed microbials can also include bacteria, fungi, or yeast products.
Do probiotics really work?
Research has demonstrated positive results with probiotics. However a probiotic's usefulness depends on many factors, including strain of bacteria, bacterial composition, health of flock, and management of the flock. The greatest effect seen with probiotic usage appears to be related to flock quality. Well-managed flocks have experienced less benefit with probiotic usage when compared to "problem" flocks.
Other alternatives for antibiotics?
Besides probiotics (or direct-fed microbials), other alternatives include supplementation with bacterial growth nutrients (ie. fermentable sugars) that may enhance the turkey's response to probiotics. In addition, several natural food products like garlic and its derivatives have also been explored as natural food products that have antibacterial properties.
In conclusion, probiotics are one alternative to antibiotics and may help to reduce food-borne pathogens like Salmonella. However, they are not a substitute for good, effective health management programs.
From Proceedings of the "Midwest Poultry Federation Convention", St. Paul, Minnesota, U.S.A.
