MOLECULAR CHARACTERIZATION AND GASTROINTESTINAL TRACT ECOLOGY OF COMMENSAL HUMAN FOOD-BORNE BACTERIAL PATHOGENS IN THE CHICKEN
Location: Poultry Microbiological Safety Research
Title: Variations in preenrichment pH of poultry feed and feed ingredients after incubation periods up to 48 hours
Submitted to: Poultry Science Association Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2011
Publication Date: July 16, 2011
Citation: Cox Jr, N.A., Buhr, R.J., Cason Jr, J.A., Richardson, K.E., Richarson, F.J., Rigsby, L.L., Cray, P.J. 2011. Variations in preenrichment pH of poultry feed and feed ingredients after incubation periods up to 48 hours. Poultry Science Association Meeting Abstract. 90:443, P.118.
Human salmonellosis outbreaks have been linked to contaminated animal feed. The literature indicates that Salmonella sustains acid injury at about pH 4.0, so we determined the pH of various preenrichment media during incubation of feed and feed ingredient samples. Five poultry finished feeds were individually added to 45 mL of four different preenrichment broths: buffered peptone water (BPW), lactose broth (LB), minimal salts medium (M-9) and universal preenrichment (UP) and incubated at 37oC for 18, 24, and 48 h. In addition to the finished feeds, ground feed ingredients were tested following the protocol for finished feeds. After each incubation period the pH was determined using a calibrated (at pH 4 and 7) pH meter and the entire experiment was replicated three times with very little variation among reps.
With finished feeds, longer incubation time did not alter pH greatly, although a slightly lower pH was observed at 48h compared to 18h and 24h. With the broiler, broiler breeder and layer feeds, the pH ranged from 3.9 - 4.7 with all the media except UP. For UP the range was 4.7 - 5.3. Overall the lowest pH values were with LB and BPW broths with the lowest pH values of 3.9 with LB for broiler breeder feed. The pH’s were slightly higher for turkey grower and turkey breeder feeds ranging from 4.4 - 5.5. With feed ingredients, a similar pattern was observed with LB and BPW producing the lowest pH’s with ground corn (3.7 - 4.7), wheat middlings (3.8 - 4.2), DDG (3.8 - 4.1), sorghum (3.9 - 4.5) and soybean meals (4.4 - 4.6); moderate to slight drop in pH with fish meal, beef or pork meat and bone meal, poultry byproduct and canola meals. Overall, UP and M-9 broths were more resistant to a drop in pH than LB and BPW broths. Low pH can impair ability of the organism to metabolize certain biochemicals that are critical in the identification process for this organism. If this injury and lack of biochemical utilization is occurring during the analysis of feed, Salmonella may be present within the sample and go undetected.