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Necrotic Enteritis: Managing without Antibiotics
Dr. Linnea J. Newman
Schering-Plough Animal Health
(presented at the PIC's Poultry Health Conference on November 14, 2000)
The medical community has expressed concern that antibiotic use in food animals may promote the development ofantibiotic-resistant strains of bacteria that could threaten the human population. While the true relationship betweenantibiotic use in animals and antibiotic-resistant bacteria in humans has yet to be determined, there has been a strong outcryfrom consumers to eliminate antibiotic use from food animal production.
What is an "antibiotic"?Webster's dictionary defines an antibiotic as a "substance or semisynthetic substance derived from a microorganism andable in dilute solution to inhibit or kill another microorganism" . Technically, this definition includes not only familiarantibiotics like penicillin, bacitracin, virginiamycin, tylosin, and lincomycin; but also includes the ionophore anticoccidials.
In July 1999, the European community banned the use of feed-grade antibiotics, including bacitracin and virginiamycin butdid not extend the ban to include ionophore anticoccidials.
Control of Necrotic Enteritis without AntibioticsThe Number 1 problem faced by poultry producers in the absence of antibiotics is necrotic enteritis and, where ionophore anticoccidials are still an option, the antibiotic effect of the ionophore can often maintain control of the disease without theuse of additional feed-grade antibiotics.
Where ionophores are not an option, necrotic enteritis is a part of antibiotic-free production! The trick is to keep it attolerable levels. No antibiotic-free producer gets by without some necrotic enteritis on almost every farm.
The following is a list of steps which may be taken to keep necrotic enteritis at "tolerable levels" in the absence ofionophores or antibiotics. Product recommendations are not based on scientific literature, but upon actual recommendationsby current antibiotic-free producers as "stuff that works".
1. Control Intestinal Disruptiona) Chemical AnticoccidialsNicarbazin, robenedine, diclazuril, halifuginone, zoalene, amprolium, clopidol or decoquinate can be used to very effectivelycontrol coccidiosis, as long as the field strains are sensitive. Unfortunately, since many chemical anticoccidials are so veryeffective, resistance builds quickly. Frequent rotation becomes essential, and may not be enough to maintain sensitivity tothe limited number of choices. Necrotic enteritis will appear with a vengeance if the coccidial control begins to falter.
b) Coccidial VaccinesLive oocyst vaccines can be used to effectively control coccidiosis. Live vaccination, however, does produce a "reaction"which causes some intestinal disruption. Even if mild, intestinal disruption may trigger secondary necrotic enteritis.
• Uniform vaccine coverage is essential to minimize reaction.
• Day-of-age application minimizes reaction because younger chickens are more resistant to infection.
One live oocyst vaccine, Coccivac-B® is composed of coccidial oocysts collected in the late 1940's and early 1950's, beforecurrent anticoccidials were discovered. This vaccine will shed anticoccidial-sensitive strains into vaccinated hoses, renewingthe sensitivity of the house oocyst population.
Coccivac-B® can be used in lieu of chemical anticoccidials, for chemical and antibiotic-free production. Vaccination mayalso be rotated with the chemicals to renew the coccidial population within the houses, and to prevent the buildup of
resistance to the limited chemical anticoccidial programs during coldest months (minimum ventilation, greatest littermoisture) and vaccination programs during the rest of the year.
C) Intestinal Irritation: Ration FormulationDiets must be formulated to avoid ingredients that irritate the intestinal mucosa. Wheat, barley, and triticale are grains thatare known to slow the intestinal transit time, which appears to irritate the intestine. Milo also appears to cause someirritation. A corn-soy ration is the best diet for antibiotic-free programs. Where wheat-based diets must be used, limit thepercentage of wheat and use feed enzymes designed to improve the digestibility of the grain. Expect a higher incidence ofnecrotic enteritis in these flocks.
Note: US producers avoid wheat-based diets for antibiotic-free production, so I do not have any specific enzyme productrecommendations. The producers in Western Canada will have the most experience in this area!
2. Control Litter MoistureMy personal field observations indicate that high litter moisture encourages necrotic enteritis. This may even apply to the slightly increased moisture on the inlet end of a tunnel-ventilated house. We are attempting to develop a quantitativecorrelation between litter moisture and necrotic enteritis, but in the meantime:• Maintain litter depth of at least 3 inches (7.5 cm) to absorb moisture;• Use absorbent litter material (wood shavings or rice hulls, do not use crop residue or straw );• Use low stocking density (20 birds per m 2 is best; 13-15 birds per m 2 may be possible, but higher density means moremoisture to dissipate);• Use nipple drinkers, and make certain that they are in good repair;• Ventilate! Ventilate! VENTILATE!
3. Control Access to BacteriaInfection is caused when bacterial numbers overwhelm the flock's ability to resist infection. If we can reduce the bacterialload, we have a better chance of avoiding clinical infection.
Note: Where products are mentioned by name, it represents specific endorsement by some of my antibiotic-free customers. Itdoes not mean that other products might not work equally well or better!
• Clean houses thoroughly after each flock. (Litter moisture control is so critical that I would rather re-use litter than clean out and replace it with only 2-3 cm of fresh litter, which in not absorbent enough!) Sweep and blow down the dust.
• Fumigate the house or use a very strong disinfectant. If available, a product called Oo-cide by Antech International, Ltd. will kill coccidial oocysts, reducing the house coccidial challenge.
• Treat dirt floors with salt (28 kg/300m 2 cheap grade cattle feeding salt).
• Treat litter with PLT®, Alum, Al Clear®, or other litter treatment.
• Treat water with a buffered acid or chlorine compound. Compounds which have been tried with success include:AquaClean® HydroClean® Aquatize® or Sodium Chlorite @ 4 - 8 ppm in final drinking water, available in 2% solution orin bulk concentrate at 25%.
These products are used from day 1 to market age, but discontinue one day before vaccination and use vaccine stabilizer toneutralize the disinfectant effect (water applied vaccination, not spray vaccines).
• Maintain supplemental feed through day 12. It is critical to avoid litter-picking, since this encourages ingestion ofexcessive bacteria and coccidial oocysts from the litter. Be especially careful of feed access when removing supplementalfeed and when moving the birds to the full house!• Pay close attention to lighting programs! Do not drop light so suddenly or so long that birds have trouble finding feed.
• Maintain good biosecurity practices: minimize the opportunity to introduce pathogens to the house with plastic boots anddisinfectant footbaths at the door.
4. Flock's Resistance to InfectionWhile reducing the bacterial load, we also need to support the flocks' ability to resist infection:
• Pay close attention to brooding, including the second week! Avoid cold stress.
• Supplement vitamins and trace minerals at a higher-than-normal level in the ration (check the %CV for these nutrientlevels; you may be surprised at how erratic they are!)• If necrotic enteritis breaks occur, support the flock with a complete vitamin pack via drinking water during the recoveryphase.
• Check the bursa and thymus and vaccinate as needed to maintain immune system integrity.
5. Competitive ExclusionUse a competitive exclusion product to keep the balance of intestinal microflora healthy, reducing the chances of aClostridium "bloom". The antibiotic-free producers who use competitive exclusion indicate that a combination of hatcheryspray and inclusion of CE products in the feed has the most impact on necrotic enteritis.
Products:• Primalac (Star Labs - 816-667-5396_ as both hatchery spray and feed additive.
• Aviguard (Bayer Labs - awaiting approval in North America) by hatchery spray and by drinking water.
• Bio-Mos (Alltech).
6. Intense Preventative Water Acidification or DisinfectionNecrotic enteritis in antibiotic-free flocks often follows a somewhat predictable pattern, which may be program-specific. Ifyou can establish a predictable pattern on your farm, you can introduce strong water acidification or disinfection through the"problem" period to minimize losses. The same acidification programs may be used as a treatment after a break starts, butlosses will be greater:• PI 6045®• Perform Max® or• Virkon® at 1 lb per gallon of stock solution (1:128 via proportioner).
These are used for 7 days during the typical "break" period, to minimize the severity of the break, or for 5 to 7 days after thefirst sign of a break.
Remember, even if every single step enumerated above is followed to the letter, you will still experience some necrotic enteritis on an antibiotic-free program without ionophores. If the breaks become severe (and they can result in 20 -50% mortality if unchecked), the only effective treatment is to return to antibiotics or sulfadimethoxine.
Fabrication Guidelines Fabrication Guidelines Table of contents Section 1 Safety Rules When handling HI-MACS® Section 2 HI-MACS® Colours Product availability HI-MACS® Adhesive colours Section 3 Sheet Specification Specification Data Sheet Chemical Resistance Section 4 Health & Safety
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