Costs to broiler producers associated with subclinical (mild) necrotic enteritis (SNE) were estimated using published information on impacts on body weight and feed conversion rate (FCR) associated with SNE and costs and revenues associated with broiler production. Estimates were expressed in U.S. dollars from the perspective of poultry producers. SNE was estimated to result in a 12% reduction in body weight and a 10.9% increase in FCR compared with healthy birds. For the purposes of this analysis, we considered scenarios involving hypothetical flocks of 20,000 birds raised to final body weights ranging from 4.63 to 7.94 lb. The incidence of SNE was assumed to occur at 20% based on the literature. For flocks raised for the length of time required to reach these target weights, SNE resulted in a loss to producers ranging from US$878.19 to US$1480.52 per flock. When feed costs required to obtain SNE flocks having a total live body weight equal to equivalent healthy flocks at market age were calculated, the increased cost to producers ranged from US$370.49 to US$739.38 per flock. SNE has the potential to cause a significant negative economic impact in broiler flocks. Strategies to reduce the incidence of SNE may help to increase the profitability of broiler production.

Two studies were conducted to examine the effects of dietary inclusion of fumaric acid on performance and carcass composition of broiler chickens. Fumaric acid was added to nutritionally complete diets at levels of 0, .125, .25, and .5% and fed from 1 to 49 days under simulated commercial conditions. In one trial, samples of birds were processed to determine dressing percentage and abdominal fat content. In the first trial (mixed sex broilers), the addition of .125% fumaric acid significantly (P less than .05) improved 49-day body weight of females and average weight gain of both sexes with no effect on feed utilization. Feed consumption was significantly increased when diets contained .125 or .50% fumaric acid. In the second trial (male broilers), 49-day body weight was significantly (P less than .05) improved by the addition of .125 and .25% fumaric acid. There were no significant differences in feed consumption; feed utilization was improved by the addition of all levels of fumaric acid. Dietary fumaric acid had no adverse effects on dressing percentage, abdominal fat content, or mortality rate.

Two similar trials were conducted to evaluate the effects of dietary inclusion of fructooligosaccharide (FOS) on live performance and carcass characteristics of broilers and on incidence and level of salmonellae on prechill broiler carcasses. The FOS was fed at two levels (0 and .375%) in a complete factorial arrangement with two levels (0 and 55 mg/kg) of bacitracin methylene disalicylate (BMD) in nutritionally complete diets. Broilers were grown to 49 days of age, and samples were processed to determine dressing percentage, abdominal fat content, and most probable number salmonellae on prechill carcasses. The addition of FOS to nutritionally complete broiler diets at .375% had little consistent effect on growth rate, feed utilization, mortality, carcass dressing percentage, abdominal fat content, or incidence or severity of salmonellae contamination of processed broiler carcasses. There appeared to be an antagonism between FOS and BMD on both live performance and salmonellae contamination of processed broiler carcasses.

The efficacy of bacitracin methylene disalicylate (BMD) in the management of necrotic enteritis (NE) when fed in combination with narasin was investigated in a floor-pen study of 2,000 broiler chickens using a Clostridium perfringens inoculum challenge model. Treatments consisted of 1) nonchallenged-nonmedicated; 2) challenged-nonmedicated; 3) challenged-narasin (70 ppm); 4) challenged-BMD (55 ppm); 5) challenged-narasin (70 ppm) + BMD (55 ppm). Medication was provided in the feed from Day 0 to trial termination on Day 41. C. perfringens challenge occurred from Day 14 to 16. BMD and narasin, fed alone and in combination, reduced (P < 0.05) mortality due to NE when compared to challenged-nonmedicated birds. NE lesion scores (Days 0 through 41) were lower among birds fed BMD and narasin, alone and in combination, compared to challenged-nonmedicated birds. Improvements in NE mortality and NE lesion scores were greatest for the BMD + narasin-medicated birds, followed by the BMD-alone, and then narasin-alone treated birds. BMD and narasin, alone and in combination, provided improvements (P < 0.05) in average daily gains over the entire study (Days 0 to 41). The results of this study demonstrate the effectiveness of BMD and narasin in the management of NE in broiler chickens.

Three experiments were conducted to determine the effects of feeding broilers formic acid (FA) or calcium formate (CF) on performance and microbiological characteristics of broilers. Live bird performance was not adversely affected by feeding up to 1.0% FA or 1.45% CF. In Experiment 1, levels of salmonellae in carcass and cecal samples were significantly reduced by feeding birds .36% CF. Salmonellae were not isolated from any of the carcasses of birds fed .36% CF. Similar reductions were not noted for total organisms or presumptive coliforms. In Experiment 2, feeding .36% CF nonsignificantly reduced levels of salmonellae in carcass and cecal samples, but again, levels of total organisms and coliforms were not reduced. In Experiment 3, salmonellae in the ceca or in the carcass rinse fluid were not reduced by feeding .36% CF.

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