Bedding and bedding management practices are associated with mesophilic and thermophilic spore levels in bulk tank raw milk

Abstract

Mesophilic and thermophilic spore-forming bacteria represent a challenge to the dairy industry, as these bacteria are capable of surviving adverse conditions associated with processing and sanitation and eventually spoil dairy products. The dairy farm environment, including soil, manure, silage, and bedding, has been implicated as a source for spores in raw milk. High levels of spores have previously been isolated from bedding, and different bedding materials have been associated with spore levels in bulk tank (BT) raw milk; however, the effect of different bedding types, bedding management practices, and bedding spore levels on the variance of spore levels in BT raw milk has not been investigated. To this end, farm and bedding management surveys were administered and unused bedding, used bedding, and BT raw milk samples were collected from dairy farms (1 or 2 times per farm) across the United States over 1 yr; the final data set included 182 dairy farms in 18 states. Bedding suspensions and BT raw milk were spore pasteurized (80°C for 12 min), and mesophilic and thermophilic spores were enumerated. Piecewise structural equation modeling analysis was used to determine direct and indirect pathways of association among farm and bedding practices, levels of spores in unused and used bedding, and levels of spores in BT raw milk. Separate models were constructed for mesophilic and thermophilic spore levels. The analyses showed that bedding material had a direct influence on levels of spores in unused and used bedding as well as an indirect association with spore levels in BT raw milk through used bedding spore levels. Specific bedding and farm management practices as well as cow hygiene in the housing area were associated with mesophilic and thermophilic spore levels in unused bedding, used bedding, and BT raw milk. Notably, levels of spores in used bedding were positively related to those in unused bedding, and used bedding spore levels were positively related to those in BT raw milk. The results of this study increase the understanding of the levels and ecology of mesophilic and thermophilic spores in raw milk, emphasize the possible role of bedding as a source of spores on-farm, and present opportunities for dairy producers to reduce spore levels in BT raw milk.

Bacterial spore levels in bulk tank raw milk are influenced by environmental and cow hygiene factors

“…Miller et al (2015b) also found that the use of straw bedding was associated with lower incidence of thermophilic spore counts in bulk tank raw milk. Similarly, a recent study of spore levels in new (unused) and used bedding and bulk tank raw milk across 18 states found that mesophilic and thermophilic spore levels in new bedding directly and indirectly affected the mesophilic and thermophilic spore levels in bulk tank raw milk (Murphy et al, 2019). Further, Murphy et al (2019) reported that bedding management practices, such as how often bedding was topped up or changed was significantly associated with spore levels in bulk tank raw milk, further supporting our findings.…”

“…Similarly, a recent study of spore levels in new (unused) and used bedding and bulk tank raw milk across 18 states found that mesophilic and thermophilic spore levels in new bedding directly and indirectly affected the mesophilic and thermophilic spore levels in bulk tank raw milk (Murphy et al, 2019). Further, Murphy et al (2019) reported that bedding management practices, such as how often bedding was topped up or changed was significantly associated with spore levels in bulk tank raw milk, further supporting our findings. Given that dairy cows spend 12 to 14 h each day lying down (Gomez and Cook, 2010), with direct contact between teat and udder surfaces and bedding, it is unsurprising that spores in bedding and bedding management are important variables in the transmission of spores into bulk tank raw milk.…”

“…Similarly, Huck et al (2008) examined spores in bedding, feed, manure, soil, and water samples on one farm in New York state and found spore levels ranged from 2.57 to 6.08 log cfu/g or mL. A survey of spores in various lactating cow bedding materials on dairy farms across 18 states in 2016-2017 found that mesophilic and thermophilic spores levels, particularly in organic bedding materials (e.g., manure solids), ranged from 3.21 to 6.03 log cfu/g and 2.79 to 5.41 log cfu/g, respectively (Murphy et al, 2019). Thus, consistent evidence shows that several farm environments harbor high spore levels that could lead to contamination of raw milk.…”

A Brief Discussion on Curdling Technology, Microbiological Risks and Contaminants of Fermented Milk Named Biisim Missiga

“…The level of this contamination is closely related to hygienic conditions of milking, state cleanliness of animal, material used, environment, knowledge and to application the good practices of rules hygiene by the actors (Maiwore et al, 2018;Millogo et al, 2018;Cissé et al, 2019). Some microorganisms pass transiently into their food producing toxins or spores, which after ingestion are very fatal for consumers (Murphy et al, 2019;Xiong et al, 2019). The presence of certain contaminants does not render this food completely unfit for human consumption, but depends the limited dose.…”

Interventions designed to control postpasteurization contamination in high-temperature, short-time-pasteurized fluid milk processing facilities: A case study on the effect of employee training, clean-in-place chemical modification, and preventive maintenance programs

“…The main organisms involved in PPC associated with finished product spoilage are heat-labile gram-negative bacteria, including Pseudomonas and the Enterobacteriaceae, which can be introduced into finished products from a variety of potential sources, including contaminated equipment, contaminated aerosols, and cross-contamination from employees (Sunga et al, 1970;Schröder, 1984;Eneroth et al, 2000b). Although thermoresistant gram-positive bacteria, including sporeformers, could also be introduced after pasteurization (Eneroth et al, 2001), endospores formed by these bacteria are often present in the raw milk supply (Murphy et al, 2019) and endospore numbers are typically not reduced by HTST. While psychrotolerant sporeformers and, to a much lesser extent, non-spore-forming gram-positive bacteria cause fluid milk spoilage, they are thus excluded from our PPC definition used in this publication.…”