Factors that affect colony forming units in bulk milk of north Antioquia-Colombia dairy farms Factores que afectan el recuento de UFC en la leche en tanque en hatos lecheros del norte de Antioquia-Colombia

Abstract

In Antioquia-Colombia, the primary milk production is mainly performed at the northern "altiplano" region using both manual and automatic milking systems. The product quality will define its commercialization directly to consumers after pasteurization or for processing and derivates production. In both cases, the initial microbial contamination is crucial for its final use. Colombian regulations, specific for regions, define the allowed values of colony forming units (CFU), so the producers not only can sell their production, but also obtain important price bonus. The objective of the present work was to study some factors that can affect the bulk milk CFU counts in northern Antioquia dairy farms. The dependent variable was measured, described with an unvaried analysis and associated with a logistic regression. CFU, and independent variables as milking system, altitude, milking time in churn (minutes), distance to bulk (m) and cow number were measured, analyzed and associated with univariated and logistic regression statistics. Results indicated that the main risk factor in the CFU variation was 148 the time period that the milk remained out of the cold chain. Other critical factors were the number of milked cows, since it increases the milking time; equally, altitude where farms are located, possibly related to temperature and bacterial proliferation.