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SUMMARY. The efficacy of narasin in the control of necrotic enteritis (NE) was investigated in a floor pen study of 2000 broiler chickens using a Clostridium perfringens feed inoculum challenge model. Treatments were 1) nonmedicated, nonchallenged; 2) nonmedicated, challenged; 3) narasin, nonchallenged; 4) narasin, challenged. Narasin was administered at 70 ppm in the feed from day 0 to trial termination on day 41. Challenge inoculum contained approximately 1 X 108 colony-forming units CP/ml and was administered from day 14 to day 16. In the unmedicated groups, challenged birds had significantly (P 0.05) and significantly (P < 0.05) lower huddling scores on days 16 and 17 than unmedicated. Coccidiosis lesion scores were zero for birds euthanatized from all treatment groups on day 17, suggesting that the beneficial effects of narasin were not due to prevention of coccidiosis. This study thus provides evidence that narasin is effective in the prevention of necrotic enteritis in broiler chickens.

The type of drinker used for poults influenced the level of free available chlorine (FAC) in chlorinated water as well as the total plate count, fecal coliform count, and number of salmonellae in chlorinated and non-chlorinated drinking water. Nipple drinkers maintained higher levels of FAC in drinking water than Swish-cups, Swish-cups maintained higher levels than MarkIII, and MarkIII maintained higher levels than trough drinkers. The level of FAC retained in the water in trough drinkers was insufficient to exert a bactericidal effect against coliforms and salmonellae. Chlorination of drinking water and the resulting diminished number or absence of salmonellae in the drinking water did not lower the number of salmonellae per gram of cecal contents in challenged or unchallenged but exposed poults. The number of salmonellae per gram of cecal contents decreased significantly (P less than 0.01) in poults between 14 and 21 days of age, irrespective of whether or not the poults drank chlorinated water.

The oral administration of a 1:20 (wt/vol) dilution of adult turkey cecal contents to poults on the day of hatching protected more than 80% of the poults against challenge at 24 hr of age with approximately 10(3) colony-forming units (CFU) of a nalidixic-acid-resistant strain of Salmonella typhimurium. All untreated poults similarly challenged were colonized. Protection was lost when the challenge dose was 10(6) or greater. When the microflora treatment followed salmonella challenge by 6 hours or more, protection was reduced. If poults were colonized by S. typhimurium, the organisms were found always in the ceca and infrequently in other parts of the intestinal tract. When poults shedding salmonella were mixed with treated poults, more than 70% of the latter remained free of the organism.

In laboratory trials, a fourth-passage culture of adult chicken cecal contents was protective against challenge with Salmonella typhimurium in turkey poults raised on wood-shavings poultry litter. The culture was not protective against pre-treatment exposure to hatchery-introduced S. bredeney and was inhibited in poults that had received an antibiotic injection at the hatchery. The inhibitory effect of the hatchery antibiotic could be avoided if the cecal-culture treatment was delayed by 3 to 4 days after antibiotic injection. Under field conditions, there was a significant reduction in the salmonella contamination of turkeys and their environment when cecal culture was given to poults raised on wood-shavings litter sprayed with a quaternary ammonium compound. When used alone, both the cecal culture and the litter disinfectant were ineffective in preventing the establishment of S. heidelberg infection. Further studies are required to confirm the possibility of a synergistic effect between the two treatments. For the control of salmonella in turkeys, use of cecal cultures may be limited by the interference of antibiotics and by their failure to protect against pretreatment exposure to salmonella.

The effect of manipulating adult turkey cecal contents was assessed. Treatment of day-old poults with cecal contents diluted up to 1/3000 protected 90% of the birds against subsequent challenge with 10(3) colony-forming units of Salmonella typhimurium. The addition of penicillin G and streptomycin to adult cecal contents reduced their protective effects by 20% and 50%, respectively. When cecal contents were heat-treated at 65 C for 15 minutes or filter-sterilized, the protective properties were lost. Anaerobic cultures of cecal contents in reinforced clostridial medium afforded protection against challenge, but protection was lost on subsequent subcultures. Thioglycollate broth culture of cecal contents did not protect.

SUMMARY The effect of manipulating adult turkey cecal contents was assessed. Treatment of day-old poults with cecal contents diluted up to 1/3000 protected 90% of the birds against subsequent challenge with 103 colony-forming units of Salmonella typhimurium. The addition of penicillin G and streptomycin to adult cecal contents reduced their protective effects by 20% and 50%, respectively. When cecal contents were heat-treated at 65 C for 15 minutes or filter-sterilized, the protective properties were lost. Anaerobic cultures of cecal contents in reinforced clostridial medium afforded protection against challenge, but protection was lost on subsequent subcultures. Thioglycollate broth culture of cecal contents did not protect. RESUMEN

The type of drinker used for poults influenced the level of free available chlorine (FAC) in chlorinated water as well as the total plate count, fecal coliform count, and number of salmonellae in chlorinated and non-chlorinated drinking water. Nipple drinkers maintained higher levels of FAC in drinking water than Swish-cups, Swish-cups maintained higher levels than MarkIII, and MarkIII maintained higher levels than trough drinkers. The level of FAC retained in the water in trough drinkers was insufficient to exert a bactericidal effect against coliforms and salmonellae. Chlorination of drinking water and the resulting diminished number or absence of salmonellae in the drinking water did not lower the number of salmonellae per gram of cecal contents in challenged or unchallenged but exposed poults. The number of salmonellae per gram of cecal contents decreased significantly (P less than 0.01) in poults between 14 and 21 days of age, irrespective of whether or not the poults drank chlorinated water.

The various manifestations of poultry diseases associated with Escherichia coli have been recently reviewed (20). The etiology and pathogenesis of the disease, with special reference to 0 groups concerned, were studied by workers in the U.S.A. (2,5,11) and Great Britain (14,21) and on the Continent (19,22). Although the disease has been recognized in Canada, no serological identification of strains has been published. This paper reports biochemical and serological findings of E. coli strains of avian origin isolated mainly in Ontario (95%). A considerable increase in the incidence of disease associated with E. coli has become evident in Ontario. Perhaps this is due, in part, to increased awareness of the disease entities described in the literature (7,8,10,12,13,20). There is little doubt that colisepticemia and other E. coli disease syndromes are difficult to define because of their complex pathogenesis (1,4,6). In this respect, an effort was made to isolate strains of E. coli from cases in which it was considered significant as a cause of disease, as done by workers in Great Britain (21). The association of certain carbohydrate fermentation patterns, particularly of dulcitol and salicin, was studied in relation to the virulence of the organisms (15,18).