Number of infusions
Research to date indicates there is little, if any, value in treating cows at drying off with multiple infusions, where multiple infusions refers to treating twice at drying off, or at dry off and at some later time. Subsequent treatments may pose the additional risk of forcing bacteria into the gland as well as increase the risk of antibiotics in milk after freshening. However, in some countries, in some seasons, and in some high-risk environments, particular problems (e.g., summer mastitis) may warrant additional treatment three weeks prior to calving, subject to veterinary advice. An alternate strategy to provide continuous protection throughout the dry period may be to infuse an internal teat sealant in combination with an antibiotic at time of dry off.
Preventing drug residues
Attention must be given to preventing drug residues in milk and meat. Label directions must be followed exactly to avoid drug residues after freshening, especially when cows have shorter than normal dry periods. Tests are available to determine antibiotic residues in milk. Most dairy cooperatives and direct milk purchasers and many veterinary clinics will run these tests. Kits are available for use on-farm. If the dry period is unexpectedly short or additional treatment has been used, or when any other doubt exists, then each cow should be tested before consigning milk.
Sanitation/Dry cow management
Because udders are not milked during the dry period, pathogens are not flushed out of the lower portion of the teat canal. This may lead to new intramammary infections, especially by skin colonizing staphylococci. The number of new infections is related to the bacterial population on teat ends. Therefore, exercise lots, loafing areas, stalls, and maternity pens should be clean and dry. Animals on pasture should not be allowed in ponds and muddy areas.
Dry cow treatment may be helpful in preventing new infections during the early dry period. However, the udder is vulnerable to new infections during the last two or three weeks of the dry period, when dry cow therapy is no longer effective. Special attention must be given to springing cows and heifers. These animals must be kept clean and dry if mastitis is to be avoided during early lactation. Weather permitting, a clean grassy lot of paddock is an ideal calving area. A clean box stall with clean bedding, preferably straw or inorganic bedding, is recommended during inclement weather. In the week immediately prior to calving, it is valuable to examine the udder daily and to use an effective teat dip on all teats.