Benefits of dietary antibiotic and mannanoligosaccharide supplementation for poultry
As in many industries, the global paradigm is shifting from an emphasis on efficiency to one of public security. Nothing demonstrates this paradigm shift more clearly than issues concerning the use of antibiotic growth promotants. Now, antibiotics have come under increasing scrutiny by some scientists, consumers and government regulators because of the potential development of antibiotic-resistant human pathogenic bacteria after long use (Phillips, 1999; Ratcliff, 2000).
Consequently, the poultry industry must develop alternatives to antibiotic growth promotants, or at least substantially reduce the amount of antibiotics used to maintain efficient poultry production and produce safe poultry meat and egg products.
Mannanoligosaccharide (MOS) supplied by BioMos (Alltech, Inc., Lexington, Kentucky) is an alternative product to antibiotics. This paper will review the mechanisms of antibiotic action to promote growth in poultry, and compare antibiotic growth promotants with MOS through comparative studies on turkeys.
The mechanisms by which antibiotics influence gut microflora and poultry growth performance are not fully understood, but there are several proposed modes of action.
Originally defined as a biological substance produced naturally by a microorganism that inhibits growth of other microorganisms, antibiotics now include those substances created synthetically to possess certain anti-microbial abilities.
Antibiotics function by altering certain properties of bacterial cellular metabolism resulting in impaired growth or death. Some antibiotics interfere with building and maintenance of the cell wall, while others interrupt proper protein translation at the ribosomal level.
Public concern about antibiotic resistance of pathogenic bacteria stems from the emergence of vancomycin-resistant enterococci during the early 1980s.
Bernick (1999) estimates that as little as 10 percent of problems observed with microbial antibiotic resistance originate from the use of antibiotics in livestock practices. However, antibiotic resistance of indigenous E. coli in poultry has reportedly remained at a relatively high level since the 1950s (Gustafson and Bowen, 1997).
In contrast to the mode of action of most antibiotics and carbohydrate fermentation sources, MOS and possibly other oligosaccharides, serve as alternate attachment sites for Gram-negative pathogens, thereby preventing attachment onto enterocytes and subsequent enteric infection. Adherence of the pathogenic microbe to the enterocyte cell wall is thought to be a prerequisite for the onset of infection (Gibbons and Van Houte, 1975).
Mannanoligosaccharides, derived from mannans on yeast cell surfaces, act as high affinity ligands, offering a competitive binding site for the bacteria (Ofek et al., 1977). Pathogens with the mannose-specific Type-1 fimbriae adsorb to the MOS instead of attaching to intestinal epithelial cells and, therefore, move through the intestine without colonisation.
Newman (1994) reported that the presence of dietary MOS in the intestinal tract removed pathogenic bacteria that could attach to the lumen of the intestine in this manner. Mannose was shown by Oyofo et al. (1989a) to inhibit the in vitro attachment of Salmonella typhimurium to intestinal cells of the day old chicken. Then Oyofo et al. (1989b) provided evidence that dietary D-mannose was successful at inhibiting intestinal colonisation of Salmonella typhimurium in broilers.
In conclusion, MOS may elicit greater benefits than antibiotics if it is used strategically together with other non-pharmaceutical enteric conditioners, such as probiotics, fructooligosaccharids, bio-active peptides and some herbs.
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Article made possible through the contribution of North Carolina State University.