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Comparison of number of Streptococcus uberis calculated on a volume or weight basis in sand and sawdust bedding

Matthew T. GablerDepartment of Animal Science, University of Minnesota, St Paul, MN 55108.
Present address is the Department of Dairy and Animal Science, Pennsylvania State University, University Park, PA 16802.

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Jeffrey K. ReneauDepartment of Animal Science, University of Minnesota, St Paul, MN 55108.

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Ralph J. FarnsworthCollege of Agriculture, and the Department of Clinical and Population Sciences, College of Veterinary Medicine, University of Minnesota, St Paul, MN 55108.

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Abstract

Objective—To determine a method for comparing counts of Streptococcus uberis in sand and sawdust and account for the influence of weight or volume of the bedding material.

Sample Population—2 sources of kiln-dried sawdust and 2 sources of washed sand.

Procedures—Sterilized bedding material (100 ml) was weighed and uniformly distributed in an aluminum pan. Each sterilized bedding material was inoculated with a mean of 3.6 × 106 (experiment 1) or 2.4 × 107 (experiment 2) colony-forming units (CFU) of S uberis/ml of bedding material. Without allowing time for replication of S uberis, inoculated bedding materials were washed with sterile saline (0.9% NaCl) solution. A 200-ml aliquot of wash solution was serially diluted up to 2,500 times with additional saline solution and inoculated on plates containing tryptose agar with 5% sheep blood. After incubation for 48 hours, number of CFU of S uberis was counted. This procedure was replicated 19 and 16 times for each bedding material in experiments 1 and 2, respectively.

Results—Evaluation of Bonferroni 95% confidence intervals revealed significant differences for counts of S uberis calculated on a weight basis between sand and sawdust.

Conclusions and Clinical Relevance—Comparison of counts of S uberis determined on a volume basis for sand and sawdust accentuates to a lesser degree the weight difference of the bedding materials and ensures a more appropriate comparison of number of S uberis. (Am J Vet Res 2001; 62:171–173)

Abstract

Objective—To determine a method for comparing counts of Streptococcus uberis in sand and sawdust and account for the influence of weight or volume of the bedding material.

Sample Population—2 sources of kiln-dried sawdust and 2 sources of washed sand.

Procedures—Sterilized bedding material (100 ml) was weighed and uniformly distributed in an aluminum pan. Each sterilized bedding material was inoculated with a mean of 3.6 × 106 (experiment 1) or 2.4 × 107 (experiment 2) colony-forming units (CFU) of S uberis/ml of bedding material. Without allowing time for replication of S uberis, inoculated bedding materials were washed with sterile saline (0.9% NaCl) solution. A 200-ml aliquot of wash solution was serially diluted up to 2,500 times with additional saline solution and inoculated on plates containing tryptose agar with 5% sheep blood. After incubation for 48 hours, number of CFU of S uberis was counted. This procedure was replicated 19 and 16 times for each bedding material in experiments 1 and 2, respectively.

Results—Evaluation of Bonferroni 95% confidence intervals revealed significant differences for counts of S uberis calculated on a weight basis between sand and sawdust.

Conclusions and Clinical Relevance—Comparison of counts of S uberis determined on a volume basis for sand and sawdust accentuates to a lesser degree the weight difference of the bedding materials and ensures a more appropriate comparison of number of S uberis. (Am J Vet Res 2001; 62:171–173)