Fashions
Micronutrients. Deficiencies in a number of essential micronutrients have been shown to cause cows to be more susceptible to disease. Among this list are vitamins A, D, and E; zinc; selenium; and copper. One can easily rationalize that feeding diets deficient in essential micronutrients will eventually result in decreased resistance to mastitis. The two micronutrients that have been shown linked to bovine mastitis most often are vitamin E and selenium. Animals deficient in either or both of vitamin E or selenium have had higher rates of infections, more frequent cases of clinical mastitis, infections of longer duration, and more severe clinical signs that cows fed supplemented diets. The recommended limit for selenium concentration in dairy cow rations is 0.3 ppm, corresponding to an approximate intake of 3 mg/day for dry and 6 mg/day for lactating Holsteins. Little data exist to suggest that dietary selenium greater than 0.3 ppm, in the absence of interfering elements such as sulphur and calcium, results in additional enhancement of host defenses against mastitis. Dry and lactating cows should consume 1000 IU/day of vitamin E. For cows fed stored forages, vitamin E may need to be supplemented at 1000 IU/day for dry cows and at 500 IU/day for lactating cows, dependent on forage quality and dry matter intake.
Coliform Mastitis Vaccines. Vaccination against coliform mastitis has become an accepted management tool to reduce the severity of clinical signs. Escherichia coli J5, and other rough mutants, are naturally occurring structurally modified strains that have unique antigenic properties that may cause enhanced immunity to not only themselves, but also other coliform strains. Use of E. coli J5 bacterin does not prevent intramammary infections. However, the use of E. coli J5 bacterin reduces the severity and duration of mastitis. Most immunization schemes include vaccination at drying off, mid-dry period, and calving to maximize protection during the late dry period and the first month of lactation. Immunizing cows during lactation may have little value because the risk to intramammary infections decreases significantly as lactation progresses. Using coliform vaccines to treat clinical cases will not influence the coarse of the infection in most cases.