OCAMM
Seminar Series
Mastitis
and Bedding Materials
Dr. Larry Smith
Ohio State University
Mastitis is
an inflammation of the mammary glands which is primarily caused by bacteria
entering through the teat end and causing an infection. The more bacteria
placed on the teat end the greater the probability that infection and
inflammation will occur. Mastitis, the most costly disease in animal
agriculture, results in a reduction of milk yield and milk quality. The
major bacterial pathogens causing the disease can be categorized as either
contagious or environmental pathogens. Contagious pathogens are
transmitted from infected glands to uninfected glands primarily during the
milking process. Contagious pathogens tend to cause subclinical infections
that are most often detected by increased milk somatic cell counts (SCC) and are
often the cause of high herd bulk milk SCC. Significant control of
contagious pathogens is achieved by post milking teat dipping in effective
germicidal teat dips, total dry cow therapy and culling. Bedding materials
play little or no role in contagious mastitis.
The
environmental bacteria are transferred to teat ends by contact with the
environment and a major environmental contact with the teat end is bedding
materials. Infections caused by the environmental bacteria are likely to
cause a case of clinical mastitis in addition to high SCC in infected quarters.
Clinical mastitis is visually abnormal milk and is generally not added to the
herd bulk milk. Thus, the impact of environmental pathogens on herd bulk
milk SCC is reduced by comparison to the contagious pathogens. Cows are
susceptible to new environmental pathogen infections during all stages of
lactation and the dry period and increased rates of new infection are noted at
the beginning of the dry period, around calving, during summer months and rates
are higher in housed cows than cows on clean, green pastures. Risk factors
associated with housing are bedding materials, stall design, ventilation and
management of the stalls, manure in alleyways, etc.
Organic bedding materials, such as straw, sawdust, manure solids, pelleted corncobs and recycled newspaper, provide a food source for bacteria and absorb moisture whereas inorganic materials, such as sand, do not. Research indicates that bacterial contamination of teat ends is higher when cows are bedding with organic materials compared to inorganic bedding. Particle size and other properties of the bedding can also influence the amount of teat end contamination. Sawdust and wood products in general are known to contribute to coliform mastitis problems while straw bedding is often associated with increased amounts of environmental mastitis caused by Streptococcus uberis. For cows that must be housed, sand that is dry, free of clay and well maintained is preferred over organic bedding.