SURVEY OF MILK QUALITY ON U.S. DAIRY FARMS UTILIZING AUTOMATIC MILKING SYSTEMS

Milk quality parameters were recorded for U.S. dairy farms using automatic milking (AM) from August 2000 to June 2003. The first farm began milking in August 2000 and additional farms were admitted to the study as they began AM operation so that 12 AM farms were represented by June 2003. Daily records of bulk tank somatic cell count (SCC) and total bacterial count (TBC) data were analyzed and compared to corresponding data from a cohort conventional farms in Wisconsin as well as data from European AM installations. The geometric means for all farms were 268,000 cells/mL SCC and 13,300 cfu/mL TBC. There was no significant difference in SCC between AM farms and the cohort of conventional farms, but a clear and significant seasonal effect was evident for SCC for both farm types, with higher values observed during the summer months (July, August, and September). The TBC of milk from AM farms was found to be lower than that from the cohort of conventional farms, and there was some evidence of a seasonal effect on TBC for both types of farm. Both SCC and TBC decreased as the amount of time that a farm utilized AM increased.