Associations among milk quality indicators in raw bulk milk

• Published in: Journal of dairy science Vol. 92; no. 10; pp. 4978 - 4987
• Main Authors: Pantoja, J.C.F., Reinemann, D.J., Ruegg, P.L.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.10.2009; American Dairy Science Association; Am Dairy Sci Assoc; Elsevier
• Subjects: Animal productions; Animals; bacterial count; Biological and medical sciences; bulk milk; Cattle; Cell Count; Colony Count, Microbial; dairy; Dairying - methods; Enterobacteriaceae - cytology; Female; Food industries; Food Preservation; Fundamental and applied biological sciences. Psychology; Hot Temperature; Logistic Models; Milk - cytology; Milk - microbiology; milk analysis; Milk and cheese industries. Ice creams; milk composition; milk quality; Quality Control; raw milk; somatic cell count; Terrestrial animal productions; Vertebrates; bulk milk; dairy; bacterial count; milk quality; Raw milk; Quality; Dairy industry; Dairy product; Bulk; Indicator
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2009-2329

The objective of this study was to determine characteristics and associations among bulk milk quality indicators from a cohort of dairies that used modern milk harvest, storage, and shipment systems and participated in an intensive program of milk quality monitoring. Bulk milk somatic cell count (SCC), total bacteria count (TBC), coliform count (CC), and laboratory pasteurization count (LPC) were monitored between July 2006 and July 2007. Bulk milk samples were collected 3 times daily (n = 3 farms), twice daily (n = 6 farms), once daily (n = 4 farms), or once every other day (n = 3 farms). Most farms (n = 11) had direct loading of milk into tankers on trucks, but 5 farms had stationary bulk tanks. The average herd size was 924 cows (range = 200 to 2,700), and daily milk produced per herd was 35,220kg (range = 7,500 to 105,000kg). Thresholds for increased bacterial counts were defined according to the 75th percentile and were >8,000cfu/mL for TBC, >160cfu/mL for CC, and ≥310cfu/mL for LPC. Means values were 12,500 (n = 7,241 measurements), 242 (n = 7,275 measurements), and 226cfu/mL (n = 7,220 measurements) for TBC, CC, and LPC, respectively. Increased TBC was 6.3 times more likely for bulk milk loads with increased CC compared with loads containing fewer coliforms. Increased TBC was 1.3 times more likely for bulk milk with increased LPC. The odds of increased TBC increased by 2.4% for every 10,000-cells/mL increase in SCC in the same milk load. The odds of increased CC increased by 4.3% for every 10,000-cells/mL increase in SCC. The odds of increased CC increased by 1% for every 0.1°C increase in the milk temperature upon arrival at the dairy plant (or at pickup for farms with bulk tank). Laboratory pasteurization count was poorly associated with other milk quality indicators. Seasonal effects on bacterial counts and milk temperature varied substantially among farms. Results of this study can be used to aid the interpretation and analysis of indicators of milk quality intensively produced by dairy processors’ laboratories.