- Email: [email protected]
Evaluation of Litter Treatments on Salmonella Recovery from Poultry Litter1
2002 Poultry Science Association, Inc.
Evaluation of Litter Treatments on Salmonella Recovery from Poultry Litter1 Center of Excellence for Poultry Science, University of Arkansas, POSC O-114 Poultry Science, Fayetteville, Arkansas 72701
Primary Audience: Researchers, Veterinarians, Production Managers SUMMARY Evaluations were conducted to determine the efficacy of two litter amendments in reducing or eliminating Salmonella recovery from kiln-dried pine shaving based broiler litter. The litter had been exposed to one and three flocks of birds for Trials 1 and 2, respectively. Litter was placed at a 2-in. depth in 1-ft2 baking pans and autoclaved. In Trial 1, the pans were inoculated with 100 mL of 104 cfu/mL nalidixic acid-resistant Salmonella typhimurium (NAL-SAL). In Trial 2, all pans were inoculated with 50 mL of 105 cfu/mL. In Trial 1, a granulated sulfuric acid litter treatment was applied at 100 and 150 lb/1,000 ft2. In Trial 2, a sodium bisulfate amendment, or a granulated sulfuric acid litter treatment, was applied at 25, 50, 75, and 100 lb/1,000 ft2. Samples were collected 24 h postinoculation and then enumerated on XLT4 agar containing nalidixic acid. In Trial 1, the NAL-SAL control recovery rate was 4.4 log10 per sample with zero recovery for the two rates of litter treatment. Litter pH for the control samples was 6.47. Litter treatment decreased the pH to 1.95 and 1.53 for the 100 and 150 lb/1,000 ft2 rates, respectively. In Trial 2, control levels of NALSAL were 2.77 log10 per sample. NAL-SAL levels increased to levels greater than those observed for the control at the litter treatment rate of 25 lb/1,000 ft2 for both treatments. A treatment level of 100 lb/1,000 ft2 was required for both litter treatments to decrease NAL-SAL to levels significantly different from the control. In Trial 2, the treatment of 100 lb/1,000 ft2 decreased litter pH to 2.67 and 3.47, respectively, for the granulated sulfuric acid and sodium bisulfate treatments. Key words: litter amendments, Salmonella, poultry litter 2002 J. Appl. Poult. Res. 11:239–243
DESCRIPTION OF PROBLEM Pathogenic bacterial populations can have a negative effect on the production and health of birds if concentrations are too high. Bacteria cause numerous disease conditions including necrotic enteritis, botulism, gangrenous dermatitis, air sacculitis, and cellulitis. In addition, pathogenic bacterial populations are also linked to 1 2
current food safety concerns at processing plants, and, because of these concerns, the Food Safety Inspection Service (FSIS) has mandated that poultry processing plants follow Hazard Analysis Critical Control Point (HACCP) programs to control pathogenic bacteria. The poultry industry is currently evaluating the feasibility of implementing pathogen reduction programs at the farm level. Should pathogen
Published with the approval of the director of the Arkansas Agricultural Experiment Station; Manuscript No. 01022. To whom correspondence should be addressed: [email protected].
Downloaded from http://japr.oxfordjournals.org/ at Serials Section, Dixson Library on June 2, 2015
J. B. Payne, E. C. Kroger, and S. E. Watkins2
JAPR: Research Report
240
(Trial 1). A separate study (Trial 2) was conducted to determine if application rates of a granulated sulfuric acid litter treatment or a sodium bisulfate litter treatment would effectively reduce the populations of Salmonella.
MATERIALS AND METHODS Bedding material was obtained from a commercial broiler house of the University of Arkansas, which is 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 in. in 1-ft2 baking pans. All pans were then covered with aluminum foil and autoclaved for 45 min at 121°C for sterilization. Pans were then removed from the autoclave and allowed to cool to room temperature. Trial 1 Three hours before treatment, all pans were inoculated with 100 mL of 104 cfu/mL nalidixic acid-resistant Salmonella typhimurium (NALSAL). The inoculation volume of 100 mL was chosen due to its ability to provide coverage of the litter surface. There were four replicate pans of litter per treatment. The two treatments were top-dressed onto the litter as recommended by the manufacturer. The recommended rate was 50 to 100 lb/1,000 ft2. The four control pans were untreated. The treatments consisted of a granulated 40% sulfuric acid litter treatment applied at 100 or 150 lb/1,000 ft2. A total of 12 pans of litter was used. Surface and core samples were collected from each pan 24 h posttreatment. Surface samples were collected using a sterile cellulose sponge hydrated with sterile skim milk. Core samples that were 1 in. in depth and that weighed 25 g were also collected. All samples were then placed into 225 mL of Butterfield’s phosphate diluent and enumerated by direct plating onto XLT4 agar containing nalidixic acid, which was incubated at 35°C for 24 h [6]. Nalidixic acid was added to the media to facilitate the selective growth of NAL-SAL. Litter pH and moisture content were determined in all groups 24 h postapplication. A 25-g sample was collected, placed into 225 mL of distilled
Downloaded from http://japr.oxfordjournals.org/ at Serials Section, Dixson Library on June 2, 2015
control begin at the farm level, integrators and growers will be challenged to reduce pathogens during growout. Recently, it has been reported [1] 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 of the broilers to consume contaminated litter in the broiler house during the withdrawal period. Salmonella recovered from carcasses in poultry processing plants could be due to fecal shedding onto the litter, which may lead to heavy contamination of feathers and feet [2]. Many integrators and growers are currently faced with disposal problems of used litter, which leads to reuse of litter over an extended period. This reuse could compromise the poultry producer’s ability to follow proper sanitation procedures and best management practices (BMP). Growers may then rely on the use of litter amendments and disinfectants as their sole source of solving problems associated with diseases caused by high levels of bacteria. Unfortunately, to decrease 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, at low pH, pathogen growth is inhibited (e.g., Salmonella, Escherichia coli 0157:H7) [3, 4, 5]. Should a litter treatment be an effective method of reducing food pathogens in the litter, 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 environment, contamination of the exterior body should be lowered, thus reducing pathogen recovery at the processing plant. A study was conducted to determine if the application of a granulated sulfuric acid litter treatment at different levels would effectively reduce Salmonella populations in used litter
PAYNE ET AL: LITTER TREATMENTS AND SALMONELLA RECOVERY
241
TABLE 1. Effect of different granulated sulfuric acid levels on nalidixic acid-resistant Salmonella typhimurium (NALSAL) counts obtained from experimentally inoculated litter
Litter treatment Control Sulfuric acid
Level (lb/1,000 ft2) — 100 150
NAL-SAL (log10/mL) core
pH
3.64a 0b 0b 0.0001
4.4a 0b 0b 0.0001
6.47a 1.95b 1.53b 0.0001
Values within a column with different superscripts are significantly different (P < 0.05).
a,b
water, shaken vigorously, and then the pH was measured. Trial 2 Three hours prior to treatment, all pans were inoculated with 50 mL of 105 cfu/mL NALSAL. The inoculation volume was reduced in order to lessen the amount of moisture added to the litter, thus producing a more accurate simulation of commercial production conditions. Each treatment was assigned to 16 pans with four application rates of 25, 50, 75, and 100 lb/1,000 ft2. Replicates of four were used for each rate along with four additional untreated pans serving as the control. The treatments consisted of a granulated 40% sulfuric acid litter treatment and a 93.2% sodium bisulfate litter treatment. Both treatments were top-dressed onto the litter as recommended by the manufacturer. Recommended rates were 50 to 100 lb/1,000 ft2 for both amendments. Core samples measuring 0.5 in. in depth and weighing 25 g were collected 24 h posttreatment. In Trial 2, only core samples were taken, due to a better recovery rate observed compared to surface samples. All samples were then enumerated following the same procedures used in Trial 1. Litter pH and moisture content were determined in all groups 24 h postapplication. Statistical Procedure Results were analyzed using the ANOVA procedure of SAS software [7]. All counts were converted to log10 values prior to analysis. Significantly different means at P < 0.05 were separated by a repeated t-test.
RESULTS AND DISCUSSION In Trial 1, application of the granulated sulfuric acid product at 100 and 150 lb/1,000 ft2
resulted in lowering NAL-SAL to undetectable levels when compared to the control pans. This reduction was observed in core and surface samples. Significant (P < 0.05) reductions were observed for litter pH, compared to the control, when both rates were applied (Table 1). In Trial 2, as compared to the untreated control pans, both litter amendments resulted in significantly (P < 0.05) lower levels of NAL-SAL when used at 100 lb/1,000 ft2 (Table 2). Also, compared to the control pans, significant (P < 0.05) differences of NAL-SAL levels were not observed for either litter amendment when used at 25, 50, or 75 lb/1,000 ft2. As mentioned before, only core samples were taken for Trial 2. All application rates used for both treatments did significantly (P < 0.05) lower pH levels, compared to the control, with the highest application rate having the most significant (P < 0.05) effect. Moisture content remained consistent for all treatments including the control (Table 2). Litter amendments are often times applied below the manufacturer’s recommended levels to decrease costs. When this practice is used on older litter with high pH levels, lesser amounts of treatment may merely be lowering the litter pH to levels ideal for bacterial growth. Another consideration is the possibility of creating litter pathogens somewhat tolerant to litter treatments by exposing the pathogens to sublethal amounts of treatment. It has been shown that Salmonella typhimurium can adapt to acidic environments when first exposed to mildly acidic conditions (pH 5.8) [4]. This adaptation would, in turn, enable the organism to better cope with environmental stresses [8]. According to Trial 2, rates of 100 lb/1,000 ft2 for the two litter treatments tested were required to significantly lower levels of Salmonella in litter. In Trial 1, the granulated sulfuric
Downloaded from http://japr.oxfordjournals.org/ at Serials Section, Dixson Library on June 2, 2015
P-value
NAL-SAL (log10/mL) surface
JAPR: Research Report
242
TABLE 2. Effect of various levels of different treatments on nalidixic acid-resistant Salmonella typhimurium (NALSAL) counts obtained from experimentally inoculated litter
Litter treatment Control Sulfuric acid
— 25 50 75 100 25 50 75 100
SEM P-value
NAL-SAL (log10/mL) core
pH
Moisture content (%)
2.770abc 3.435a 2.843abc 2.281bcd 1.727d 3.011ab 2.091cd 2.164cd 1.471d 0.360 0.0075
8.300a 5.825bc 4.425d 3.550e 2.675f 6.233b 5.475c 4.425d 3.475e 0.272 0.0001
23.6 25.4 24.3 23.8 23.8 23.3 23.3 25.6 25.0 0.813 0.7610
Values within a column with different superscripts are significantly different (P < 0.05).
a–f
acid product applied at 100 and 150 lb/1,000 ft2 did reduce NAL-SAL to undetectable levels, although this reduction was not observed for the 100-lb. application rate in Trial 2. A possible explanation for this occurrence could be the difference in inoculation volumes for both trials. Trial 1 received a higher inoculation volume of 100 mL, whereas Trial 2 received 50 mL of inoculum. The higher inoculation volume would increase the litter moisture content, possibly causing an increased activation of the litter amendment, which may explain why we observed a complete reduction of NAL-SAL in Trial 1. The lower pH observed in Trial 1 versus
Trial 2 could be due to the fresher litter used in Trial 1, which had a lower initial pH. With lower initial pH and organic matter, thus lower ammonia levels produced, the litter did not have a strong buffering capacity against the litter treatments. Litter amendments are not the sole solution for disease problems. BMP 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 might potentially be reduced with proper sanitation procedures and the correct use of litter treatments.
CONCLUSIONS AND APPLICATIONS 1. An application rate of 100 lb/1,000 ft2 for the granulated sulfuric acid and the sodium bisulfate litter amendments was required in order to significantly lower NAL-SAL levels compared to the control. 2. Low level application of litter amendments to older litter with a high pH may, at times, merely reduce the pH to levels more optimal for bacterial growth. 3. The results of this study indicate that variables such as litter pH and litter age should be carefully considered when determining rates of litter amendment application for the reduction of Salmonella in poultry litter.
REFERENCES AND NOTES 1. 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. Poult. Sci. 78:45–49.
Downloaded from http://japr.oxfordjournals.org/ at Serials Section, Dixson Library on June 2, 2015
Sodium bisulfate
Level (lb/1,000 ft2)
PAYNE ET AL: LITTER TREATMENTS AND SALMONELLA RECOVERY 2. Trampel, D. W., R. J. Hasiak, L. J. Hoffman, and M. C. Debey. 2000. Recovery of Salmonella from water, equipment, and carcasses in turkey processing plants. J. Appl. Poult. Res. 9:29–34. 3. Chung, K. C., and J. M. Goepfert. 1970. Growth of Salmonella at low pH. J. Food Sci. 35:325–328. 4. Foster, J. W. 1995. Low pH adaptation and the acid tolerance response of Salmonella typhimurium. Crit. Rev. Microbiol. 21:215–237. 5. Guraya, R., J. F. Frank, and A. N. Hassan. 1998. Effectiveness of salt, pH, and diacetyl as inhibitors for Escherichia coli
243
O157:H7 in dairy foods stored at refrigeration temperatures. J. Food Prot. 61:1098–1102. 6. Food and Drug Administration. 1992. Bacteriological Analytical Manual. 7th ed. Food and Drug Admin., Assoc. Off. Anal. Chem., Arlington, VA. 7. SAS Institute. 1999. SAS User’s Guide. Version 8.1. SAS Institute Inc., Cary, NC. 8. Leyer, G. J., and E. A. Johnson. 1993. Acid adaptation induces cross-protection against environmental stresses in Salmonella typhimurium. Appl. Environ. Microbiol. 58:1842–1847.
Downloaded from http://japr.oxfordjournals.org/ at Serials Section, Dixson Library on June 2, 2015
Evaluation of Litter Treatments on Salmonella Recovery from Poultry Litter1 Center of Excellence for Poultry Science, University of Arkansas, POSC O-114 Poultry Science, Fayetteville, Arkansas 72701
Primary Audience: Researchers, Veterinarians, Production Managers SUMMARY Evaluations were conducted to determine the efficacy of two litter amendments in reducing or eliminating Salmonella recovery from kiln-dried pine shaving based broiler litter. The litter had been exposed to one and three flocks of birds for Trials 1 and 2, respectively. Litter was placed at a 2-in. depth in 1-ft2 baking pans and autoclaved. In Trial 1, the pans were inoculated with 100 mL of 104 cfu/mL nalidixic acid-resistant Salmonella typhimurium (NAL-SAL). In Trial 2, all pans were inoculated with 50 mL of 105 cfu/mL. In Trial 1, a granulated sulfuric acid litter treatment was applied at 100 and 150 lb/1,000 ft2. In Trial 2, a sodium bisulfate amendment, or a granulated sulfuric acid litter treatment, was applied at 25, 50, 75, and 100 lb/1,000 ft2. Samples were collected 24 h postinoculation and then enumerated on XLT4 agar containing nalidixic acid. In Trial 1, the NAL-SAL control recovery rate was 4.4 log10 per sample with zero recovery for the two rates of litter treatment. Litter pH for the control samples was 6.47. Litter treatment decreased the pH to 1.95 and 1.53 for the 100 and 150 lb/1,000 ft2 rates, respectively. In Trial 2, control levels of NALSAL were 2.77 log10 per sample. NAL-SAL levels increased to levels greater than those observed for the control at the litter treatment rate of 25 lb/1,000 ft2 for both treatments. A treatment level of 100 lb/1,000 ft2 was required for both litter treatments to decrease NAL-SAL to levels significantly different from the control. In Trial 2, the treatment of 100 lb/1,000 ft2 decreased litter pH to 2.67 and 3.47, respectively, for the granulated sulfuric acid and sodium bisulfate treatments. Key words: litter amendments, Salmonella, poultry litter 2002 J. Appl. Poult. Res. 11:239–243
DESCRIPTION OF PROBLEM Pathogenic bacterial populations can have a negative effect on the production and health of birds if concentrations are too high. Bacteria cause numerous disease conditions including necrotic enteritis, botulism, gangrenous dermatitis, air sacculitis, and cellulitis. In addition, pathogenic bacterial populations are also linked to 1 2
current food safety concerns at processing plants, and, because of these concerns, the Food Safety Inspection Service (FSIS) has mandated that poultry processing plants follow Hazard Analysis Critical Control Point (HACCP) programs to control pathogenic bacteria. The poultry industry is currently evaluating the feasibility of implementing pathogen reduction programs at the farm level. Should pathogen
Published with the approval of the director of the Arkansas Agricultural Experiment Station; Manuscript No. 01022. To whom correspondence should be addressed: [email protected].
Downloaded from http://japr.oxfordjournals.org/ at Serials Section, Dixson Library on June 2, 2015
J. B. Payne, E. C. Kroger, and S. E. Watkins2
JAPR: Research Report
240
(Trial 1). A separate study (Trial 2) was conducted to determine if application rates of a granulated sulfuric acid litter treatment or a sodium bisulfate litter treatment would effectively reduce the populations of Salmonella.
MATERIALS AND METHODS Bedding material was obtained from a commercial broiler house of the University of Arkansas, which is 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 in. in 1-ft2 baking pans. All pans were then covered with aluminum foil and autoclaved for 45 min at 121°C for sterilization. Pans were then removed from the autoclave and allowed to cool to room temperature. Trial 1 Three hours before treatment, all pans were inoculated with 100 mL of 104 cfu/mL nalidixic acid-resistant Salmonella typhimurium (NALSAL). The inoculation volume of 100 mL was chosen due to its ability to provide coverage of the litter surface. There were four replicate pans of litter per treatment. The two treatments were top-dressed onto the litter as recommended by the manufacturer. The recommended rate was 50 to 100 lb/1,000 ft2. The four control pans were untreated. The treatments consisted of a granulated 40% sulfuric acid litter treatment applied at 100 or 150 lb/1,000 ft2. A total of 12 pans of litter was used. Surface and core samples were collected from each pan 24 h posttreatment. Surface samples were collected using a sterile cellulose sponge hydrated with sterile skim milk. Core samples that were 1 in. in depth and that weighed 25 g were also collected. All samples were then placed into 225 mL of Butterfield’s phosphate diluent and enumerated by direct plating onto XLT4 agar containing nalidixic acid, which was incubated at 35°C for 24 h [6]. Nalidixic acid was added to the media to facilitate the selective growth of NAL-SAL. Litter pH and moisture content were determined in all groups 24 h postapplication. A 25-g sample was collected, placed into 225 mL of distilled
Downloaded from http://japr.oxfordjournals.org/ at Serials Section, Dixson Library on June 2, 2015
control begin at the farm level, integrators and growers will be challenged to reduce pathogens during growout. Recently, it has been reported [1] 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 of the broilers to consume contaminated litter in the broiler house during the withdrawal period. Salmonella recovered from carcasses in poultry processing plants could be due to fecal shedding onto the litter, which may lead to heavy contamination of feathers and feet [2]. Many integrators and growers are currently faced with disposal problems of used litter, which leads to reuse of litter over an extended period. This reuse could compromise the poultry producer’s ability to follow proper sanitation procedures and best management practices (BMP). Growers may then rely on the use of litter amendments and disinfectants as their sole source of solving problems associated with diseases caused by high levels of bacteria. Unfortunately, to decrease 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, at low pH, pathogen growth is inhibited (e.g., Salmonella, Escherichia coli 0157:H7) [3, 4, 5]. Should a litter treatment be an effective method of reducing food pathogens in the litter, 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 environment, contamination of the exterior body should be lowered, thus reducing pathogen recovery at the processing plant. A study was conducted to determine if the application of a granulated sulfuric acid litter treatment at different levels would effectively reduce Salmonella populations in used litter
PAYNE ET AL: LITTER TREATMENTS AND SALMONELLA RECOVERY
241
TABLE 1. Effect of different granulated sulfuric acid levels on nalidixic acid-resistant Salmonella typhimurium (NALSAL) counts obtained from experimentally inoculated litter
Litter treatment Control Sulfuric acid
Level (lb/1,000 ft2) — 100 150
NAL-SAL (log10/mL) core
pH
3.64a 0b 0b 0.0001
4.4a 0b 0b 0.0001
6.47a 1.95b 1.53b 0.0001
Values within a column with different superscripts are significantly different (P < 0.05).
a,b
water, shaken vigorously, and then the pH was measured. Trial 2 Three hours prior to treatment, all pans were inoculated with 50 mL of 105 cfu/mL NALSAL. The inoculation volume was reduced in order to lessen the amount of moisture added to the litter, thus producing a more accurate simulation of commercial production conditions. Each treatment was assigned to 16 pans with four application rates of 25, 50, 75, and 100 lb/1,000 ft2. Replicates of four were used for each rate along with four additional untreated pans serving as the control. The treatments consisted of a granulated 40% sulfuric acid litter treatment and a 93.2% sodium bisulfate litter treatment. Both treatments were top-dressed onto the litter as recommended by the manufacturer. Recommended rates were 50 to 100 lb/1,000 ft2 for both amendments. Core samples measuring 0.5 in. in depth and weighing 25 g were collected 24 h posttreatment. In Trial 2, only core samples were taken, due to a better recovery rate observed compared to surface samples. All samples were then enumerated following the same procedures used in Trial 1. Litter pH and moisture content were determined in all groups 24 h postapplication. Statistical Procedure Results were analyzed using the ANOVA procedure of SAS software [7]. All counts were converted to log10 values prior to analysis. Significantly different means at P < 0.05 were separated by a repeated t-test.
RESULTS AND DISCUSSION In Trial 1, application of the granulated sulfuric acid product at 100 and 150 lb/1,000 ft2
resulted in lowering NAL-SAL to undetectable levels when compared to the control pans. This reduction was observed in core and surface samples. Significant (P < 0.05) reductions were observed for litter pH, compared to the control, when both rates were applied (Table 1). In Trial 2, as compared to the untreated control pans, both litter amendments resulted in significantly (P < 0.05) lower levels of NAL-SAL when used at 100 lb/1,000 ft2 (Table 2). Also, compared to the control pans, significant (P < 0.05) differences of NAL-SAL levels were not observed for either litter amendment when used at 25, 50, or 75 lb/1,000 ft2. As mentioned before, only core samples were taken for Trial 2. All application rates used for both treatments did significantly (P < 0.05) lower pH levels, compared to the control, with the highest application rate having the most significant (P < 0.05) effect. Moisture content remained consistent for all treatments including the control (Table 2). Litter amendments are often times applied below the manufacturer’s recommended levels to decrease costs. When this practice is used on older litter with high pH levels, lesser amounts of treatment may merely be lowering the litter pH to levels ideal for bacterial growth. Another consideration is the possibility of creating litter pathogens somewhat tolerant to litter treatments by exposing the pathogens to sublethal amounts of treatment. It has been shown that Salmonella typhimurium can adapt to acidic environments when first exposed to mildly acidic conditions (pH 5.8) [4]. This adaptation would, in turn, enable the organism to better cope with environmental stresses [8]. According to Trial 2, rates of 100 lb/1,000 ft2 for the two litter treatments tested were required to significantly lower levels of Salmonella in litter. In Trial 1, the granulated sulfuric
Downloaded from http://japr.oxfordjournals.org/ at Serials Section, Dixson Library on June 2, 2015
P-value
NAL-SAL (log10/mL) surface
JAPR: Research Report
242
TABLE 2. Effect of various levels of different treatments on nalidixic acid-resistant Salmonella typhimurium (NALSAL) counts obtained from experimentally inoculated litter
Litter treatment Control Sulfuric acid
— 25 50 75 100 25 50 75 100
SEM P-value
NAL-SAL (log10/mL) core
pH
Moisture content (%)
2.770abc 3.435a 2.843abc 2.281bcd 1.727d 3.011ab 2.091cd 2.164cd 1.471d 0.360 0.0075
8.300a 5.825bc 4.425d 3.550e 2.675f 6.233b 5.475c 4.425d 3.475e 0.272 0.0001
23.6 25.4 24.3 23.8 23.8 23.3 23.3 25.6 25.0 0.813 0.7610
Values within a column with different superscripts are significantly different (P < 0.05).
a–f
acid product applied at 100 and 150 lb/1,000 ft2 did reduce NAL-SAL to undetectable levels, although this reduction was not observed for the 100-lb. application rate in Trial 2. A possible explanation for this occurrence could be the difference in inoculation volumes for both trials. Trial 1 received a higher inoculation volume of 100 mL, whereas Trial 2 received 50 mL of inoculum. The higher inoculation volume would increase the litter moisture content, possibly causing an increased activation of the litter amendment, which may explain why we observed a complete reduction of NAL-SAL in Trial 1. The lower pH observed in Trial 1 versus
Trial 2 could be due to the fresher litter used in Trial 1, which had a lower initial pH. With lower initial pH and organic matter, thus lower ammonia levels produced, the litter did not have a strong buffering capacity against the litter treatments. Litter amendments are not the sole solution for disease problems. BMP 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 might potentially be reduced with proper sanitation procedures and the correct use of litter treatments.
CONCLUSIONS AND APPLICATIONS 1. An application rate of 100 lb/1,000 ft2 for the granulated sulfuric acid and the sodium bisulfate litter amendments was required in order to significantly lower NAL-SAL levels compared to the control. 2. Low level application of litter amendments to older litter with a high pH may, at times, merely reduce the pH to levels more optimal for bacterial growth. 3. The results of this study indicate that variables such as litter pH and litter age should be carefully considered when determining rates of litter amendment application for the reduction of Salmonella in poultry litter.
REFERENCES AND NOTES 1. 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. Poult. Sci. 78:45–49.
Downloaded from http://japr.oxfordjournals.org/ at Serials Section, Dixson Library on June 2, 2015
Sodium bisulfate
Level (lb/1,000 ft2)
PAYNE ET AL: LITTER TREATMENTS AND SALMONELLA RECOVERY 2. Trampel, D. W., R. J. Hasiak, L. J. Hoffman, and M. C. Debey. 2000. Recovery of Salmonella from water, equipment, and carcasses in turkey processing plants. J. Appl. Poult. Res. 9:29–34. 3. Chung, K. C., and J. M. Goepfert. 1970. Growth of Salmonella at low pH. J. Food Sci. 35:325–328. 4. Foster, J. W. 1995. Low pH adaptation and the acid tolerance response of Salmonella typhimurium. Crit. Rev. Microbiol. 21:215–237. 5. Guraya, R., J. F. Frank, and A. N. Hassan. 1998. Effectiveness of salt, pH, and diacetyl as inhibitors for Escherichia coli
243
O157:H7 in dairy foods stored at refrigeration temperatures. J. Food Prot. 61:1098–1102. 6. Food and Drug Administration. 1992. Bacteriological Analytical Manual. 7th ed. Food and Drug Admin., Assoc. Off. Anal. Chem., Arlington, VA. 7. SAS Institute. 1999. SAS User’s Guide. Version 8.1. SAS Institute Inc., Cary, NC. 8. Leyer, G. J., and E. A. Johnson. 1993. Acid adaptation induces cross-protection against environmental stresses in Salmonella typhimurium. Appl. Environ. Microbiol. 58:1842–1847.
Downloaded from http://japr.oxfordjournals.org/ at Serials Section, Dixson Library on June 2, 2015