Herd level measures of health and productivity in Prince Edward Island dairy herds

Herd level measures of health and productivity in Prince Edward Island dairy herds, computed monthly over a 4 year period, were evaluated. Descriptive statistics for 11 key measures of health and productivity were computed. The parameters cover the areas of milk production, reproductive performance, mastitis and milk quality. Many parameters exhibited considerable within-herd variation, suggesting that monthly values must be converted into a rolling average before then could be used reliably. Six of the 11 parameters exhibited a distinct seasonal pattern and seasonally adjusted values were obtained for those parameters. In general, the seasonally adjusted values had smaller within-herd variation than the non-adjusted values. For each parameter, the month-to-month variability was determined for both the original monthly values and monthly values of a 3 month weighted rolling average. The 90th percentiles of these month-to-month changes were used as a threshold to identify 'large' fluctuations in a herd's performance. Guidelines for the interpretation of each of the 11 parameters are presented.