Factors associated with use of prostaglandins in reproductive herd health programs for dairy cows.

Use of prostaglandin F2 alpha products (PG) in dairy cows was studied by use of computerized reproductive herd health data compiled from 29 dairy herds in Minnesota and Wisconsin during 1983 through 1988. Treatment with PG was recorded in 1,856 of 7,139 (26.0%) complete lactations. More than 1 treatment with PG was administered in 534 of the 1,856 (28.8%) lactations in which PG were used. The proportion of lactations in which treatment was used varied among herds and years, and was associated with the proportion of cows in which natural breeding was attempted and, to a lesser extent, with estrus detection index and conception rates; these associations were potentially modified by time between veterinary herd health visits. Calving-to-treatment intervals (mean +/- SD) were 100.4 +/- 55.1 days for first treatments only, and 116.2 +/- 66.1 days for all treatments. These values varied considerably among herds and years and among reasons for treatment. Much of the variation in proportions of lactations in which treatment was used and in the time of treatment within lactations could not be accounted for with the variables included in this study, and was probably related to individual considerations for each cow.