Feed borne antibiotic growth promoters (AGP) have been fed to livestock in the US and other countries for about 50 years to improve growth performance. Early indications of improved performance in poultry were reported by Moore et al. (1946). However, most of the AGP labels list no specific claims to control disease. Debate over the generation of antibiotic resistance among bacteria such as Escherichia coli (E. coli) and Salmonella has generated the strongest objection to using antibiotics. Antibiotic resistance of indigenous E. coli of poultry has remained at a relatively high level since the 1950's. In the US, reports from the Institute of Medicine and the Council for Agricultural Science and Technology recommended reduction or elimination of AGP in livestock feeds even though neither of these reports provided evidence proving that AGP resistant microorganisms were responsible for contributing to antibiotic-resistant infections in humans. Although this debate continues, there is interest in developing alternatives to AGP such as probiotics. The term “probiotic” has generally referred to live cultures fed to poultry and livestock in an attempt to improve the animal’s intestinal health and, therefore, the animal’s performance.

Alternatives to antibiotics, such as competitive exclusion (CE) treatments, have been developed to encourage a protective barrier of bacteria in the digestive tract of poultry to prevent the colonization of growth depressing and/or pathogenic microorganisms. Some CE cultures have included undefined normal avian gut microflora or have included defined cultures using bacteria such as Lactobacillus spp. The reduction or elimination of Salmonella from the intestinal tract of poultry is of special interest because of the prevalence of human food borne diseases caused by Salmonella with poultry products serving as a vehicle for human salmonellosis.

The term “probiotic” has been used to refer to feed additives that contained both live cultures and other products such as non-digestible feed ingredients that enhance host digestive tract microflora. This would include many of the indigestible sugars such as oligosaccharides. Therefore, the Association of American Feed Control Officials and the US Food and Drug Administration have recommended the term “direct-fed microbials” (DFM) be used to describe live culture feed additives. Other types of probiotics that are not live cultures have been referred to as “prebiotics”. There are numerous reports of DFM, including Lactobacillus spp., being fed to poultry including turkeys. However, there are few reports where the feed containing the DFM was pelleted.

Therefore, the objectives of a recent study at NCSU were to determine 1) the effect of a dietary DFM on turkey poult performance, 2) the susceptibility of turkey poults fed a DFM to Salmonella challenge, and 3) the effect of feed pelleting on the efficacy of the dietary DFM.

Day-of-hatch Large White female poults were placed in two rooms and fed one of four dietary feed treatments. One room housed non- Salmonella challenged poults while in the other room , poults were challenged with an oral dose of Salmonella. A single batch of starter ration was split into four parts and used to provide four dietary treatments: 1. mash feed with no DFM, 2. mash feed with DFM (Primalac® 0.9 kg/ ton feed), 3. pelleted and crumbled feed with no DFM, and 4 pelleted and crumbled feed with DFM. Liver, spleen, total and lower intestinal tract weights and intestinal length and most probable number Salmonella populations were determined for a sample of birds from each treatment. Feeding processed feed resulted in improved 3 week body weight and feed conversion as expected. Feeding the DFM improved 3 week feed conversion in birds not dosed with Salmonella. Salmonella populations were slightly reduced by feeding DFM.

The commercial DFM product tested in this study resulted in improved poult performance similar to results reported with broilers using the same product and also reduced intestinal Salmonella colonization and changes in intestinal morphology. These effects were independent of feed processing. Further work with market age turkeys, both in pen studies and in field trials, is warranted.

May 2008