Minimum of 6 ml milk each sample
Freeze samples immediately after collection. Samples must remain cold, preferably frozen. See Submission Guidelines for more information on how to collect a bulk tank milk sample.
The Pre-Incubation Count is the number of bacteria per ml of milk which survive incubation at 12.8° C (55° F) for 18 hours. This test is commonly performed in conjunction with an SPC for comparison of results. A high SPC will result in a high PI count, however, if hygiene practices are poor the PI may be significantly higher than the SPC.
For more information on interpreting PI test results and troubleshooting high PI counts, see "The Preliminary Incubation Count for Raw Milk".