Association between product quality control and process quality control of bulk milk

Assessment of dairy-milk quality is based on product quality control (testing bulk-milk samples) and process quality control (auditing dairy farms). It is unknown whether process control improves product quality. To quantify possible association between product control and process control a statistical analysis was conducted. The analysis comprised 64.373 audit results on 26,953 dairy farms and all conducted lab tests of bulk-milk samples two, six or 12 months before the audit. Lab results included somatic cell count (SCC), total bacterial count (TBC), antimicrobial drug residues (ADR), level of butyric acid spores (BAS), freezing point depression (FPD), level of free fatty acid (FFA), and cleanliness of the milk (CLN). Results show that numerous audit variables are related to bulk-milk lab results, although the goodness of fit of the models is generally low. Cleanliness of cattle, berths, parlor and the tank room are positively correlated with superior product-quality, mainly with respect to SCC, TBC, BAS, FPD, FFA and CLN. Animal-health and/or veterinary medicine management relate to SCC, FPD, FFA, and CLN, the availability of drinking water to TBC, BAS, FFA, and CLN and maintenance of the milking equipment relates mainly to SCC, FPD, FFA. Summarizing, product quality control and process quality control of bulk milk are to some degree associated: if dairy farms are assessed negatively on specific audit aspects the bulk-milk quality is more likely to be inferior