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Quantification of microbial populations in organic and inorganic dairy cattle bedding materials
The objective of this study was to quantify differences in microbial populations of four different bedding types used in dairy barns: 1) deep bedded new sand (NS), 2) deep bedded recycled sand (RS), 3) deep bedded organic solids (DBOS), and 4) shallow bedded organic solids on top of mattresses with foam cores (SBOS). Weekly composite bedding samples were systematically collected from selected locations within randomly selected stalls in each of four identical pens containing 32 freestalls and approximately 28 lactating cows during the 49 week study period. Microbial populations were determined by plating 10 μL inoculations of duplicate sets of serial dilutions (10-1 to 10-5) on three selective medias. Bacterial groups were quantified as: Gram-negative (total growth on MacConkey’s agar), coliforms (lactose positive colonies on MacConkey’s agar), Klebsiella (red to pink colonies on MacConkey inositol-carbenicillin agar), and Streptococci spp. (total growth on Edward’s modified medium agar). The relationship between bacterial populations and bedding type was analyzed in a repeated measures model using PROC MIXED (SAS 9.3). The model included effects of bedding type with sampling date repeated. Yi = α + β1 Xi1 + β2 Xi2 +ei where Yi is the log10 CFU count for bedding sample i from pen Xi1 and date Xi2.
Table. Bacteria isolated from different dairy cattle bedding types (Log10CFU/g)
Bedding material |
Gram-negative |
Coliform |
Klebsiella |
Streptococci spp. |
NS |
4.72a |
3.59a |
2.41a |
6.88a |
RS |
5.25b |
4.10b |
3.19b |
7.21b |
SBOS |
5.81c |
4.08b |
2.74ab |
8.16c |
DBOS |
6.83d |
5.70c |
5.05c |
7.08ab |
a,b,c,dValues with different letters in the same column differ significantly (P ≤ 0.02).
Bacterial counts differed among bedding materials. Fewer bacteria were isolated from NS as compared to other bedding materials with the exception of Klebsiella in SBOS and Streptococci spp. in DBOS. More bacteria were isolated from DBOS compared with other bedding materials except for Streptococcispp. in sand bedding. Distribution of bacteria varies among bedding types. In general, NS had the fewest bacteria while DBOS contained the most bacteria.
Keywords: Bacteria, Bedding, Dairy