Milking time hygiene interventions on dairy farms reduce spore counts in raw milk

Abstract

Spore-forming bacteria, such as Paenibacillus spp. and Bacillus spp., can survive HTST pasteurization in spore form and affect the quality of dairy products (e.g., spoilage in fluid milk). With the demand for higher quality finished products that have longer shelf lives and that can be distributed further and to new markets, dairy processors are becoming interested in obtaining low-spore raw milk supplies. One method to reduce spores in the dairy system will require disrupting the transmission of spores from environmental locations, where they are often found at high concentrations (e.g., manure, bedding), into bulk tank raw milk. Previous research has suggested that cow hygiene factors (e.g., udder hygiene, level of spores in milk from individual cows) are important for the transmission of spores into bulk tank raw milk, suggesting that one potential strategy to reduce spores in bulk tank milk should target cow hygiene in the parlor. To that end, we conducted a study on 5 New York dairy farms over a 15-mo period to evaluate the effect of a combination of intervention strategies, applied together, on the levels of aerobic spores in bulk tank raw milk. The combination of interventions included (1) training milking staff to focus on teat-end cleaning during milking preparation, and (2) implementing changes in laundered towel preparation (i.e., use of detergent, chlorine bleach, and drying). Study design involved collecting bulk tank raw milk samples for a week before and a week after initiating the combination of interventions (i.e., training on the importance of teat-end cleaning and towel treatment). Observations on teat-end condition, udder hygiene scores, and number of kickoffs during milking were also collected for 24 h before and after implementation of the interventions. A total of 355 bulk tank raw milk samples were collected with mean mesophilic and thermophilic spore counts of 2.1 and 2.4 cfu/mL, respectively, before interventions were applied, and 1.6 and 1.5 cfu/mL, respectively, after the interventions were applied. These reductions represent decreases of 37 and 40% in bulk tank raw milk mesophilic spores and thermophilic spores, respectively. Importantly, spore reductions were observed during each of the 3 visits once the interventions were applied, and the largest reduction in spores was recorded for the first sampling after training the milking staff. Further, when a higher proportion of very rough teat ends was observed, bulk tank milk thermophilic spore counts were significantly higher. The intervention strategies tested here represent easy-to-execute cleaning strategies (e.g., focusing on teat-end hygiene and towel washing procedures) that can reduce bulk tank raw milk spore levels. Future studies should validate the effect of on-farm interventions for reduced spore raw milk on corresponding processed product quality and will need to verify the effects of these small changes on product shelf life.