Background

The reduction of E. coli O157:H7 and Salmonella spp. in both pre- and post-harvest areas continues to be a major goal of the beef industry. It has been demonstrated that cattle hides are the major source of contamination in processing plants. The reduction of E. coli O157:H7 and Salmonella spp. on cattle hides will go a long way in ensuring the safety of the beef supply. 

Researchers and beef packers/processors have addressed beef safety concerns by developing a variety of methods that are now implemented, or are being further developed, to reduce numbers of bacteria on beef and beef products and improve microbiological safety. These microbiological decontamination technologies include:

• Animal cleaning;
• Chemical dehairing at slaughter;
• Spot-cleaning of carcasses by knife-trimming or steam/hot water vacuuming; and
• Spraying/washing/rinsing of carcasses before evisceration and/or before chilling, with water, chemical solutions and/or steam or hot water.

The most commonly used decontamination strategies involve the use of water and steam at various temperatures and spray pressures. Other decontamination strategies involve the use of FDA-approved chemicals applied through water-based sprays. This study focuses on the use of a feed supplement that could decrease the prevalence of E. coli O157:H7 in cattle feces. This would decrease the pathogen load of cattle coming into the processing facility and have a positive effect on further interventions. The objective of this study was to assess the effect of octanoic acid as a pre-harvest feed supplement to decrease the prevalence of E. coli O157:H7 in cattle.

Methodology

Trial 1
Five hundred and twelve (512) feeder cattle on high-energy diets were selected for Trial 1 of this study. Half of the cattle were given octanoic acid as a feed supplement (in addition to the high-energy diet) during the last three days of finishing and half were kept on the high-energy diet throughout the trial. Since only one fecal sample was positive for E. coli O157:H7 in Trial 1, a second trial was conducted.

Trial 2
Sixty-four (64) yearling heifers were selected for Trial 2 and were inoculated with E. coli O157:H7. All of the heifers were put on high-energy diets and half were given octanoic acid as a feed supplement for three days prior to collection of fecal samples.

Findings

Trial 1
In Trial 1 only one positive E. coli O157:H7 fecal sample was found. Therefore, a second trial was conducted in which cattle were inoculated with E. coli O157:H7 so the effects of octanoic acid as a feed supplement could be assessed.

Trial 2
Supplementation with octanoic acid did not reduce the prevalence of E. coli O157:H7 in the feces of cattle. In fact, the prevalence of E. coli O157:H7 actually decreased in the cattle not administered octanoic in their feed. No octanoic acid was found in any feces samples tested. Therefore, it was concluded that none of the octanoic acid reached the large intestine, most likely because it was already metabolized in the small intestine.

Implications

The findings of this study were inconclusive due to the fact that none of the octanoic acid actually reached the large intestines of the cattle studied. Feeding cattle large enough doses of octanoic acid to pass through the rumen and small intestine into the large intestine could conceivably reduce levels of E. coli O157:H7, but this could impact the health of the animal and would not be cost effective. Lipid encapsulation technologies could be developed that delivered enough of the treatment to the large intestine, but the cost of developing this technology would outweigh the immediate effectiveness.