The Author

Dr. Susan Watkins Extension Poultry Specialist

Introduction

In addition, pathogenic bacterial populations are also linked to current food safety concerns at the processing plant. Because of these concerns, USDA –Food Safety Inspection Service (FSIS) has mandated that poultry processing plants follow HAACP programs to control pathogenic bacteria. FSIS is now evaluating the feasibility of implementing food safety regulations at the farm level.

Should pathogen control begin at the farm level, integrators and growers will be challenged to reduce pathogen production during grow-out. Corrier et al. (1999) reported that the incidence of Salmonella increased in the crop of broilers at the end of the feed withdrawal period as compared to the level of Salmonella in the crops at the beginning of the feed withdrawal period (10% versus 1.9%). The researchers speculated that the increased incidence of Salmonella was associated with an increased tendency for the broilers to consume contaminated litter in the broiler house during the withdrawal period. Trampel et al. (2000) reported that Salmonella recovered from carcasses in poultry processing plants could be due to fecal shedding onto the litter which may lead to heavy contamination of the bird’s feathers and feet.

Many integrators and growers are currently faced with disposal problems of used litter. This leads to the re-use of litter over an extended time frame which could compromise the poultry producer’s ability to follow proper sanitation procedures and best management procedures (BMP’s). Growers then may rely on the use of litter amendments and disinfectants as their sole source of solving any problems associated with diseases caused by high bacterial levels. Unfortunately, in order to cut costs, growers may apply litter amendments below manufacturer’s recommendations with the hope of accomplishing somewhat of an improvement from current conditions of the poultry house.

Litter amendments are commonly used in poultry houses for the reduction of harmful ammonia levels by lowering litter pH. It has been shown that by lowering pH levels, reduction occurs in bacterial concentrations. A study was conducted to determine if the application of Poultry Guard at different levels would effectively reduce the incidence of Salmonella in used litter (Trial 1). A separate study (Trial 2) was conducted to determine if the application of Poultry Guard and PLT (Poultry Litter Treatment) would effectively reduce the incidence of Salmonella as well as determine at what application rate reduction would occur. Should a litter treatment be an effective method of reducing food pathogens in the litter, then the potential for crop and possibly carcass contamination could be significantly reduced through the application of a litter treatment prior to implementing feed withdrawal programs. With reduced pathogens in the bird’s environment, contamination of the exterior body should be lowered, thus reducing pathogen recovery at the processing plant.

Materials and Methods

Bedding material was obtained from one of the University of Arkansas’ commercial broiler houses that serves as a contract production facility for a local poultry integrator. Prior to the experiment, the litter had been exposed to one flock for Trial 1 and three flocks for Trial 2. The original bedding material was kiln dried pine shavings. Litter was placed at a depth of 2 inches in one square foot baking pans. All pans were then covered with aluminum foil and autoclaved for 45 minutes at 121OC to sterilize the litter. Pans were then removed from the autoclave and allowed to cool to room temperature.

Trial 1

Inoculation: All pans were inoculated with 100 ml of 104 CFU/ml nalidixic acid-resistant Salmonella typhimurium (NAL-SAL). The application rate of 100 ml was chosen due to its ability to create a good coverage on the litter surface.

Treatments: There were 4 replicate pans of litter per treatment. The two treatments were top-dressed onto the litter as recommended by the manufacturer. The four control pans remained untreated. The treatments consisted of Poultry Guard at 100 and 150 lb/1000 ft² application rates. A total of twelve pans of litter were used.

Sampling techniques: Surface and core samples were collected from each pan 24 hours after application. Surface samples were collected using a sterile cellulose sponge hydrated with sterile skim milk. Core samples measuring one inch in depth and weighing 25 grams were collected. All samples were then placed into Butterfield’s Phosphate Diluent and enumerated onto XLT 4 agar containing nalidixic acid, which was incubated at 35OC. Litter pH and moisture content was determined in all groups 24 hours post application.

Trial 2

Inoculation: All pans were inoculated with 50 ml of 105 CFU/ml NAL-SAL.

Treatments: Each treatment was assigned to 16 pans with 4 application rates of 25, 50, 75, and 100 lbs/1000 ft2. Replicates of 4 were used for each rate along with 4 untreated pans serving as the control. The treatments consisted of Poultry Guard and PLT. Both treatments were top dressed onto the litter as recommended by the manufacturer. Recommended rates were 75-100 lbs/1000 ft2 for Poultry Guard and 50-100 lbs/1000 ft2 for PLT.

Sampling techniques: Core samples measuring half an inch in depth and weighing 25 grams were collected 24 hours post treatment. All samples were then placed into Butterfield’s phosphate diluent and enumerated onto XLT4 agar containing nalidixic acid, which was incubated at 35OC for 24 hours. Litter pH and moisture content was determined in all groups 24 hours post application.

Analysis Results: were analyzed using the GLM procedure of SAS. All counts were converted to log10 values prior to analyses. Significantly different means were separated using the repeated t-test.

Results

In Trial 1, the application of Poultry Guard at 100 and 150 lb/1000 ft2 resulted in lowering NAL-SAL to undetectable levels when compared to the control pans. This reduction was observed in both core and surface samples. Significant reductions were observed on litter pH, compared to the control, when both rates were applied (P=0.0001) (Table 1).

In Trial 2, as compared to the untreated control pans, both litter amendments resulted in significantly lower levels of NAL-SAL versus the control when used at the rate of 100 lbs/1000 ft2 (P=0.0075) (Table 2). Also compared to the control pans, significant differences of NAL-SAL levels were not observed for either litter amendment when used at rates of 25, 50, and 75 lbs/1000 ft2. When both treatments were applied at the 25 lbs/1000 ft2 level, Salmonella recovery was higher than the control pans. All application rates used for both treatments significantly lowered pH levels, versus the control, with the highest application rate having the most significant effect. Moisture content remained consistent for all treatments including the control.

Discussion

Litter amendments are often times applied below the manufacturer’s recommended levels to save costs. When this practice is used on older litter with high pH levels, lesser amounts of treatment may only be lowering the litter pH to ideal levels for bacterial growth. Another consideration is the possibility of creating litter pathogens somewhat tolerant to litter treatments by exposing the pathogens to sub lethal amounts of treatment.

According to Trial 2, rates of 100 lbs/1000 ft2 for the two litter treatments tested are required to significantly lower levels of NAL-SAL in litter. In Trial 1, Poultry Guard at application rates of 100 and 150 lbs/1000 ft² reduce NAL-SAL to undetectable levels, although this was not observed for the 100 lb. application rate in Trial 2. A possible explanation for this occurrence could be the difference in inoculation rates for both trials. Trial 1 received a higher inoculation rate of 100 ml while Trial 2 received a 50 ml inoculation rate. The higher inoculation rate would increase the litter moisture content, possibly causing an increased activation of the litter amendment. This may explain why we observed a complete reduction of NAL-SAL in Trial 1. Litter amendments are not the sole solution for disease problems.

BMP’s and a good sanitation program must be in place in order to maintain a successful operation. With this in mind, Salmonella found on carcasses in processing plants could potentially be reduced with proper sanitation procedures and the correct use of litter treatments.

References

Corrier, D.E., J.A. Byrd, B.M. Hargis, M.E. Hume, R.H. Bailey, and L.H. Stanker. 1999. Presence of Salmonella in the crop and ceca of broiler chickens before and after preslaughter feed withdrawal. Poultry Sci. 78:45-49.
Trampel, D.W., R.J. Hasiak, L.J. Hoffman, M.C. Debey. 2000. Recovery of Salmonella from water, equipment, and carcasses in turkey processing plants. J. Appl. Poultry Res. 9:29-34.

Source: Avian Advice - Spring 2005 - Volume 7, Number 2