Key: Clinical Mastitis Evaluation
Definitions Other useful clinical mastitis indices are:
What is a clinical case?  The definition being suggested by the AABP Mastitis Committee is 1.  Average quarters per case:
 "whenever clinical signs (abnormal milk, swollen inflamed quarter, etc.) occur in a number of quarters affected during time period
cow with saleable milk."  This is a very basic definition.  It would also include those cows number of clinical cases during the time period
with clinical signs at calving but still having unsalable colostral milk.
When is a case considered a repeat or recurring case?  In the literature the definition  2.  Average duration of treatment per case:
of what constitutes a new clinical episode varies.  A range of from 6 to 17 days recurring total number of cow treatment days during time period
clinical signs has been used as criterion.  For the purpose of routine clinical mastitis record keeping, total number of clinical cases during time period
an interval of 14 days is being suggested as a good and niversally practical criterion.
Clinical Mastitis Indices 3.  Average days milk discarded per case:
The following are being suggested as the "core" clinical mastitis indices that should be used total number of days milk discarded during time period
in monitoring clinical mastitis: total number of clinical cases during time period
1.  Clinical cases per 100 cows per month and per year:  This represents the number of   4.  Percent of cows culled because of clinical mastitis per year:
clinical cases that occurred in the lactating herd during the designated period of interest. number of cows culled for clinical cases during period
This is a good overall measure of clinical mastitis at the herd level.  Expressed either as cases average number of dry and lactating cows during time period x 100
per 100 cows or as a percentage of the lactating here, easy comparisons can be made with
research incidence data or between herds.  Goals should be set at realistic, attainable levels 5.  Percent of cows died because of clinical mastitis per year:
based on the herd's current status.
number of clinical cases during time period x 100 number of cows that die because of clinical mastitis during time period
average number of milking cows during the time period average number of dry and lactating cows during time period
2.  Percent of cows affected:  This represents the percent of lactating cows that had one 6.  Probability of a recurring case:  This calculation depends on   
or more clinical cases during the designated period.  Percent of cows affected in the herd give recording a history of recurring clinical cases at each dairy.  With the
some indication of the depth of the herd's clinical mastitis problem.  Is it a few chronic with recorded history as baseline data and assuming mastitis control practices
several recurring clinical cases, or is it an "outbreak" affecting a large number of cows? remain the same, it is possible to predict the probability that a cow with one
Calculation of the percent of cows affected by lactation number, stage of lactation, or season, etc. clinical case will have another clinical case during that lactation.  For example,
provides a tool for epidemiological analysis of the herd's clinical mastitis problem. the probability of a first lactation animal having a second case of clinical
mastitis during that lactation is equal to:
number of cows with clinical cases during period x 100
average number of milking cows during time period number of 1st lactation cows with 2 clinical cases this lactation
number of 1st lactation cows with 1 clinical case this lactation
3.  Percent lactations with more than one clinical case:  The percent of lactating cows  
that have two or more clinical cases during a lactation represent the problem cows.  These
 cows will often account for a large proportion of the total clinical mastitis * Reneau, J.K.  1993.  Clinical mastitis records in production medicine programs. 
number of cows with 2 or more clinical cases during period x 100 Compend. Contin. Educ. Pract. Vet. Vol 15(3) March 1993.
average number of milking cows during time period 1B