Importance of Pre-Milking Udder Hygiene to Reduce Transfer of Clostridial Spores from Teat Skin to Raw Milk

Abstract

Butyric acid producing clostridia (BAPC) cause the so-called late-blowing defect, a serious quality problem in semi-hard and hard cheeses. Late-blown cheeses are characterized by undesired slits and cracks, irregular eyes, and off-flavors due to excessive amounts of gas and organic acids produced by clostridia. Clostridial transfer to raw milk can occur during milking through dirty teats. Therefore, teat cleaning before milking is a key factor in preventing clostridial contamination of the milk. However, different cleaning methods are used, and little information is available on the efficacy of routine teat cleaning in reducing clostridial endospores. The main objectives of this study were to assess the extent of udder contamination with BAPC spores and to investigate the efficacy of routine teat cleaning on BAPC spore counts in milk. In a longitudinal study, eight dairy farms were visited during five sampling events. Clostridial spore counts were quantified from teat skin before and after routine teat cleaning, in pooled quarter milk samples from individual cows, and in bulk tank milk samples using a most probable number method. In addition, farm management data were collected periodically through a survey, and average cow cleanliness was assessed by a veterinarian. On average, teat cleaning resulted in a 0.6 log unit reduction in BAPC spores on teat skin, and a strong positive correlation was found between BAPC spore concentrations on teat skin after cleaning and in pooled quarter milk samples. Seasonal variations and the potential influence of differences in farm management were also noted. Interestingly, average cow cleanliness correlated strongly with BAPC spore levels in milk, suggesting the potential for a quick and rough estimation method of clostridial contamination that could be implemented by farmers.

One-Year Monitoring of Prevalence and Diversity of Dairy Propionic Acid Bacteria in Raw Milk by Means of Culture-Dependent and Culture-Independent Methods

“…If cattle are out pasture grazing during summer, they will be exposed to rain and consequently have dirtier udders compared to winter, when they remain indoors or have limited outdoor space in a free stall barn. If dPAB levels in raw milk are indeed influenced by teat cleanliness, as is the case for clostridial contamination, the higher dPAB levels in summer may be favored by dirtier udders due to pasture grazing and weather exposure [ 24 ]. Furthermore, dPAB have previously been identified on the teat surface, albeit rarely [ 38 ].…”

“…P. freudenreichii and 3dPAB levels below the limit of quantification ( LOQ ) determined by qPCR, as well as samples in which no amplification could be detected, were included in the statistical analysis; the latter with an approximation of 0 log, as all these results provide important information for model generation. To identify process variables potentially associated with dPAB contamination in raw milk, a partition decision tree, as described by Burtscher et al [ 24 ], was used. The decision tree was validated on 30% of the dataset, and variables were identified based on the results.…”

Specificity of the AMP-6000 Method for Enumerating Clostridium Endospores in Milk

“…In addition, we included isolates from the analysis of teat skin swabs to challenge the method with a matrix containing high levels of endosporeforming bacteria. Field samples were collected from eight Austrian dairy farms during five seasons in 2018 and 2019, as described by Burtscher et al [8]. The samples included pooled quarter milk (PQM; n = 631) from individual cows, bulk tank milk (BTM; n = 40) from each farm and teat swab samples (TS; n = 382).…”

“…The first aim of this study was to further evaluate the specificity of the AMP-6000 method for the enumeration of endospores of butyric acid-producing clostridia under practical conditions. For this purpose, isolates obtained from a large number of raw milk and teat skin samples were identified by matrix-assisted laser desorption/ionization timeof-flight mass spectrometry (MALDI-TOF MS) [8]. The milk samples and teat swab samples were collected and analyzed using the AMP-6000 method during a two-year monitoring study in eight Austrian dairy farms [8].…”

“…For this purpose, isolates obtained from a large number of raw milk and teat skin samples were identified by matrix-assisted laser desorption/ionization timeof-flight mass spectrometry (MALDI-TOF MS) [8]. The milk samples and teat swab samples were collected and analyzed using the AMP-6000 method during a two-year monitoring study in eight Austrian dairy farms [8].…”