ALUMNI CORNER: ACIDIC BEDDING CONDITIONER MAY LOWER RISK OF MASTITIS
Mastitis continues to be one of the most problematic diseases for dairy cows and producers. Not only does it cost the dairy industry more than a billion dollars annually, the lowered somatic cell count limits for exporting milk to the European Union put additional pressure on producers to keep SCC below 400,000 per mL to avoid potentially losing their ability to ship milk. A cow’s housing environment is the primary source of mastitis caused by Environmental strep., E. coli, Klebsiella, which may be significantly affected by proper bedding management. Organic bedding presents the greatest risk for environmental mastitis and, according to the last USDA survey, approximately 54% of freestall facilities are bedded with some form of organic bedding. One management practice that may reduce the risk of environmental mastitis was the alteration of the pH of the bedding to make it a less hospitable environment for the major pathogens.
A research team from the University of Connecticut and Washington State University evaluated the effect of an acidic clay-based bedding additive on the bedding quality and pathogen counts within sawdust bedded freestalls and teat end condition of mid-lactation Holstein dairy cows. The effectiveness of the bedding additive was compared using a control of freestalls bedded with roughly 4” of sawdust against the treated sawdust-bedded stalls (~1 lb of additive containing 45 to 65% sulfuric acid spread across the third of the stall closest to the curb and an additional 0.25 lb added to the same amount of sawdust as the control treatment). The following response variables were assessed during each 21-d period to determine the effect of the additive:
1. Teat cleanliness – Scored daily from 1 (no bedding/manure) to 4 (more than half the teat surface covered with material)
2. Stall cleanliness – The rear portion of each stall was scored daily using a 3 × 3 grid with each cell of the grid scored on a 0 (clean sawdust) to 5 (manure covering entire cell) scale.
3. Bedding samples – All sawdust used during the study was sampled for environmental pathogens before being used to bed the freestalls. On delivery as a bedding material, sawdust samples were collected on days 1, 2, 7, 14, and 21. Samples were analyzed for total gram-negative bacteria and bacteria counts. Bedding samples were also analyzed for dry matter content and pH on the same days.
4. Teat swabs – On the same days that bedding samples were collected, a swab was run over each teat end before cows were prepped for milking. These swabs were analyzed for growth of Streptococcus spp., coliform pathogens, and Klebsiella.
5. Milk samples – Milk from the right front quarter and a composite sample from all quarters, was collected on days 0, 3, 7, 14, and 21 and analyzed for SCC. Additional milk samples collected on days -4, 10, 17 (with an additional sample on day 3 of period 2) were analyzed for environmental mastitis pathogens.
6. Teat end callosity – Teat ends were scored as either smooth or rough on days 0, 7, 14, and 21
The bedding additive did not affect teat end cleanliness, teat end callosity, or somatic cell counts. No meaningful treatment differences were observed in freestall cleanliness. Total bacteria counts were greater in the control for the first two days of sampling, but by day 7 there was no difference between the two bedding management approaches. On the other hand, Environmental strep counts were greater in the control than the treatment. Counts increased over the course of the study for both control and treated sawdust. Coliform counts did not differ, but did increase over time. The additive did lower pH, but there were no differences in the overall dry matter. Fewer pathogens were found on the teats of cows housed with the treated bedding. There was a greater risk for pathogens found on the teat ends as pathogen load increased within the bedding and increased pH of the bedding.
The bedding additive worked as expected and was effective at lowering the risks of mastitis for dairy cows housed in freestalls using sawdust bedding. It still needs to be determined how practical its application may be on commercial farms. Within this study, freestalls were completely cleaned of bedding and pressure washed after 3 weeks. The additive would need to be added directly to the base of the freestall for effective use, so it would require all materials to be removed at regular intervals. Still, this may be worth the effort if current mastitis control practices are insufficient to control environmental pathogens.
— Peter Krawczel
Peter Krawczel was a graduate student at Miner Institute and earned his Ph.D. in animal behavior from the University of Vermont in 2011. Peter is now a Dairy Research and Extension Specialist in the Department of Animal Science at the University of Tennessee in Knoxville.
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