Competitive Exclusion

What the heck is competitive exclusion? Simply put, it is using "good" bacteria to control "bad" bacteria. It is a naturally occuring process in a bird's body in which the microflora in a bird's gut gives it some immunity from infection. The "good" bacteria basically blocks all the sites on the intestinal walls where infection might take hold. Rehabilitators already use probiotics for birds undergoing antibiotic treatment to help re-establish a healthy gut flora.

Shortly after hatching, a bird begins colonizing microflora from bacteria introduced by its parents during feeding and/or from the environment. Precocial chicks acquire bacteria from the ground while foraging. Altricial hatchlings acquire the bacteria from their parents and their environment (usually their nesting material). Gram positive bacteria was found in the normal flora of nuthatch nests1.

The gut microflora modifies the energy utilization of the diet (more dietary energy is needed) but its protective measures are a necessary balance. 3 Studies have shown that germ-free chicks (lacking gut microflora) had better protein and energy utilization. 4The predominant bacteria in tested chickens were Bacteroidaceae, Lactobacillus, and Escherichia coli2 and it is presumed that the microflora varies by species.2

With regard to commercial poultry hatcheries where precocial chicks are at increased risk of contamination from Salmonella outbreaks, studies have been conducted to see if introducing "good" bacteria shortly after hatching helps to build early protection against "bad" bacteria.

Initially in these studies, the oral use of pre-screened healthy adult feces was used to inoculate chicks. The inoculated chicks showed better resistance to Salmonella than the control group in the laboratory, however results varied in field studies. Benefits were greatest before 3 days of age, after which microflora concentration levels were the same for treated and untreated chicks. The effectiveness of the inoculant cultures varied, depending on the culturing process and the amount of microbes.5, 6 The obvious drawback in using fecal material is that other pathogens, and potentially parasites, may also be introduced.

New products have been commercially developed for use by the poultry industry, using highly refined methods of cultured pathogen-free "good" bacteria. Its use is believed to enhance protection, not provide complete protection.7 Preempt is one such product.

Whether competitive exclusion should be considered for rehabbing hatchlings is debatable. Rehabilitators do not have access to culturing pathogen-free bacteria for use in inoculation. Providing feces of an adult could be as harmful as it is beneficial, especially if the adult bird has not been screened for harmful bacteria and parasites. Hypothetically, a hatchling's exposure to harmful bacteria during the critical first 3 days of life are greatly reduced in a rehabilitation setting where good hygiene is maintained. Perhaps during the first few days following hatching, hatchlings have a need for higher protein and energy utilization which would be reduced by the presence of "good" bacteria. Until further studies are conducted, we'll have to determine whether the benefits outweigh the risks.

REFERENCES:
1Mehmke U, Gerlach H, Kosters J, Hausmann S., The aerobic bacterial flora of songbird nests, Dtsch Tierarztl Wochenschr 1992 Dec;99(12):478-82
2Miyamoto T, Horie T, Fukata T, Sasai K, Baba E., Changes in microflora of the cloaca and oviduct of hens after intracloacal or intravaginal inoculation with Salmonella enteritidis., Avian Dis 1998 Jul-Sep;42(3):536-44
3Muramatsu T, Nakajima S, Okumura J., Modification of energy metabolism by the presence of the gut microflora in the chicken. , Br J Nutr 1994 May;71(5):709-17
4Furuse M, Yokota H., Effect of the gut microflora on chick growth and utilisation of protein and energy at different concentrations of dietary protein., Br Poult Sci 1985 Jan;26(1):97-104
5Lafont JP, Bree A, Naciri M, Yvore P, Guillot JF, Chaslus-Dancla E., Experimental study of some factors limiting 'competitive exclusion' of salmonella in chickens., Res Vet Sci 1983 Jan;34(1):16-20
6Bailey JS, Blankenship LC, Stern NJ, Cox NA, McHan F. Effect of anticoccidial and antimicrobial feed additives on prevention of Salmonella colonization of chicks treated with anaerobic cultures of chicken feces., Avian Dis 1988 Apr-Jun;32(2):324-9
7Methner U., Administration of autochthonous intestinal microflora--a method to prevent Salmonella infections in poultry, Dtsch Tierarztl Wochenschr 2000 Oct;107(10):402-8

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