"Benchmark" - a large observational study of Ontario beef breeding herds: Study design and collection of data.

The methods used in a large field study which investigated the health and productivity of Ontario beef breeding herds are described. Beginning in the calving season of 1986, 180 breeding herds on 170 randomly sampled farms were followed for a two year period, using producer records and annual farm visits.The response (cooperation) rate among the eligible producers initially contacted was 70%. Approximately two-thirds of producers maintained individual animal records, primarily calving season records. Approximately 40% recorded disease occurrences.The advantages, disadvantages, and interpretation of "on-farm" observational studies are discussed.