Develop strategies and standards to prevent introducing intramammary infections into a herd

To prevent introducing mastitis pathogens into a herd when purchasing cows, a balance has to be struck between minimizing the probability of purchasing an infected cow and maintaining sufficient choice in the population from which to select replacements. This is also influenced by the farm attitude to risk – what degree of risk is acceptable for purchasing an infected cow.

Each farm must determine the level of biosecurity to implement in the herd, and develop their own guidelines and standards accordingly. Herman Barkema, University of Calgary, has outlined some biosecurity measures and example standards that can be followed to prevent introducing mastitis pathogens into a herd when purchasing animals.

To minimize the risk of buying infected cattle, it is sensible to set some standards that apply to the herd of origin. For example:

  • The herd must have had a rolling geometric mean herd SCC <200,000 for at least one year
  • The herd must have individual cow SCC recorded at least bimonthly for the previous six months
  • The herd should provide information on pathogens present on farm
  • The herd must not have had any history of Strep. agalactiae infection in last two years
  • The herd should be BVDV-free or vaccinated
  • The herd must not have cows with severe teat lesions
  • The herd owner must be honest and willing to give you all this information.

To minimize the risk of buying an infected cow, it is important for an individual cow to meet certain requirements. For example:

  • The cow must never have exceeded an SCC of 200,000 for life
  • The cow should at least have the three most recent SCC in current lactation <100,000
  • The cow should have been treated with a dry cow treatment if purchased in early lactation

Before adding newly purchased animals to the herd, the following steps should be taken:

  • Udder, teats and milk must be examined for signs of abnormalities on arrival
  • The cow must be CMT-negative for three consecutive days if purchased in early lactation
  • At a minimum, the cow must be milked last until all CMT tests are negative for three consecutive days
  • It should be possible to send cows back to the vendor if any mammary gland abnormalities are found within two weeks of purchase

Source: 2008 NMC Annual Meeting Proceedings, p. 64 - 74 (Barkema et al)

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