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. D escriptive statistics for 11 key measures of health and productivity w ere computed. The parameters cover the areas of milk production, repro ductive performance, mastitis and milk quality. Many parameters exhibi ted considerable within-herd variation, suggesting that monthly values must be converted into a rolling average before then could be used re liably. 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 varia tion than the non-adjusted values. For each parameter, the month-to-mo nth variability was determined for both the original monthly values an d monthly values of a 3 month weighted rolling average. The 90th perce ntiles of these month-to-month changes were used as a threshold to ide ntify 'large' fluctuations in a herd's performance. Guidelines for the interpretation of each of the 11 parameters are presented.