Longitudinal Trends and Associations between Compost Bedding Characteristics and Bedding Bacterial Concentrations

The objectives were to quantify bedding concentrations of total bacteria and selected groups of mastitis pathogens (coliforms and streptococci), to identify bedding factors associated with these bacterial populations, and to describe longitudinal variation of bedding characteristics. Bedding samples from the superficial and deep (20 cm) layers were collected biweekly during 1 year from 3 compost bedded pack (CBP) dairies. Bedding bacterial concentrations and physical-chemical characteristics (moisture, organic matter, carbon-nitrogen ratio (C/N), pH, and density) were determined. Mixed models were used to identify predictors for bacterial concentrations. Shewhart control charts were produced to describe longitudinal variation of bedding characteristics and define alerts of out-of-control variation. Bedding temperature was greater in the deep layer than on the surface (difference = 27.0, 12.1, and 14.4 °C for farms A, B and C, respectively). Except for farm B, bacterial concentrations were greater on the surface than in the deep layer. Organic matter and dry density were associated with concentration of total bacteria and coliforms. For all farms, C/N (positive association) and dry density (negative association) were associated with bedding concentration of streptococci. Deep temperature and moisture remained within the control limits defined in farm A and B during most of the period, whereas 7 and 9 alerts for temperature and moisture were observed on farm C, respectively. For all farms, organic matter, C/N, and pH exhibited great variation, resulting in several out-of-control alerts. Results of this study can be used to manage the CBP towards reducing cows’ exposure to mastitis pathogens.