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Negative influence of subclinical mastitis.

Dairy Pipeline: October 1996

by Tom Bailey
Dairy Production Medicine
Virginia-Maryland Regional College of Veterinary Medicine
Virginia Tech

The negative influence of subclinical mastitis (milk that looks normal with high somatic cell counts) on milk production is substantial. Estimates put the cost of one case of subclinical mastitis per cow in the range of $200 per year. In Virginia, the average potential loss of income to mastitis on the farm is over $20,000 per year. Generally, producers put an emphasis on clinical and underestimate the significance of subclinical mastitis, not realizing that for every 1 clinical case in the herd there are 15 to 40 subclinical cases contributing to an elevated somatic cell count. Subclinical mastitis may contribute 70 percent of the total milk loss. Virginia herds that have not been on a mastitis control program will often have as high as 50 percent of the cows infected with subclinical mastitis in an average of two quarters. A mastitis control program would begin with determining the level of subclinical mastitis. The DHIA records or a CMT of all cows is used to estimate lost production and to establish an actual dollar loss. Mastitis contributes to the loss of income in the following ways: 70 percent from lost milk production, 14 percent from death and premature culling, 8 percent milk discarded at treatment, and 8 percent in drugs and veterinary expenses. Further laboratory analysis of milk samples would indicate whether the problem is originating in the parlor or between milkings in the cow's environment. This would then allow one to target specifics in the parlor such as milking hygiene, equipment problems, teat dips, etc. When environmental bacteria are isolated, one should pay attention to the freestalls, loafing areas, feeding cows directly after milking, muddy areas, etc. A producer should seek the advise of his/her veterinarian or extension agent as to what steps to follow to initiate a mastitis control program. For every $1 invested, an effective mastitis control program can return $15 to $20 in increased milk production, decreased culling and death loss, and decreased treatment expenses.

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