Milking system and premilking routines have a strong effect on the microbial community in bulk tank milk

Abstract

In this study, we investigated the variation in the microbial community present in bulk tank milk samples and the potential effect of different farm management factors. Bulk tank milk samples were collected repeatedly over one year from 42 farms located in northern Sweden. Total and thermoresistant bacteria counts and 16S rRNA gene-based amplicon sequencing were used to characterize microbial community composition. The microbial community was in general heterogeneous both within and between different farms and the community composition in the bulk tank milk was commonly dominated by Pseudomonas, Acinetobacter, Streptococcus, unclassified Peptostreptococcaceae, and Staphylococcus. Principal component analysis including farm factor variables and microbial taxa data revealed that the microbial community in milk was affected by type of milking system. Milk from farms using an automatic (robot) milking system (AMS) and loose housing showed different microbial community composition compared with milk from tiestall farms. A discriminant analysis model revealed that this difference was dependent on several microbial taxa. Among farms using an automatic milking system, there were further differences in the microbial community composition depending on the brand of the milking robot used. On tiestall farms, routines for teat preparation and cleaning of the milking equipment affected the microbial community composition in milk. Total bacteria count (TBC) in milk differed between the farm types, and TBC were higher on AMS than tiestall farms (log 4.05 vs. log 3.79 TBC/mL for AMS and tiestalls, respectively). Among tiestall farms, milk from farms using a chemical agent in connection to teat preparation and a more frequent use of acid to clean the milking equipment had lower TBC in milk, than milk from farms using water for teat preparation and a less frequent use of acid to clean the milking equipment (log 3.68 vs. 4.02 TBC/mL). There were no significant differences in the number of thermoresistant bacteria between farm types. The evaluated factors explained only a small proportion of total variation in the microbiota data, however, despite this, the study highlights the effect of routines associated with teat preparation and cleaning of the milking equipment on raw milk microbiota, irrespective of type of milking system used.

Associations between the Bacterial Composition of Farm Bulk Milk and the Microbiota in the Resulting Swedish Long-Ripened Cheese

“…For some farms, there were major shifts over time in milk microbiota which were not correlated with changes in management, indicating that other factors, e.g., the weather during the harvesting season, contributed to the observed differences [29]. Investigating the variation in the microbiota in bulk milk collected monthly on 42 dairy farms over one year, we found that the type of dairy farm (milking system) had a strong effect on the bulk milk microbiota, an effect likely associated with hygiene routines during the pre-milking and cleaning of the milking equipment [8]. The 18 farms used in the present study were selected from among those original 42 farms and an effect of milking system on bulk milk microbiota was also clear in the present study.…”

“…Stricter hygiene on farms, including pre-milking, udder-cleaning, and teat-disinfection routines, have likely contributed to reducing the total number of bacteria in bulk milk and therefore also the number of NSLAB in the milk, with consequences for the cheese maturation process. In a recent study, we explored farm-related factors contributing to the variation in the microbial community in bulk milk from different dairy farms [8]. The results revealed an effect of routines associated with teat preparation and cleaning of the milking equipment on bulk milk microbiota, with milk from farms using an automated milking system (AMS) having different microbial composition than milk from tie-stall farms.…”

The Investigation of Changes in Bacterial Community of Pasteurized Milk during Cold Storage

“…Pseudomonas and Acinetobacter were the genera with the highest relative abundances in the bulk tank samples [37] and pasteurized milk [2]. A recent Swedish study identified Pseudomonas, Streptococcus, Acinetobacter, and Staphylococcus as the top abundant bacterial genera in tank milk [38]. The variation in bacterial community composition in raw milk could be attributed to the core microbiota present in pasteurized milk.…”

Vallkonferens 2023

“…Studien genomfördes i Västerbotten och omfattade 18 mjölkgårdar. Dessa hade tidigare deltagit i en mer omfattande studie (Priyashantha et al, 2021;Sun et al, 2022), vilket innebar att vi redan hade bakgrundsinformation om produktionen på gårdarna. En inledande intervju gjordes för att uppdatera informationen avseende rutiner, utfodring och mjölkning.…”

“…I ett tidigare projekt har vi studerat vilka faktorer på gården som påverkar tankmjölkens mikroflora (Sun et al, 2022). Studien visade att det fanns en skillnad i mikrofloran i tankmjölken kopplat till gårdarnas mjölkningssystem, där besättningar med automatisk mjölkning hade en annorlunda mikroflora jämfört med uppbundna besättningar.…”