Characterization and relationship between bulk tank milk composition and compost bedded variables from dairy barns in Rio Grande do Sul state, Brazil

Studies with compost bedded pack dairy barn system (CBDB) are still recent in Brazil. Thus, we used principal component and canonical correlation analysis to characterize and verify the relationship between compost bedded variables (CB) and bulk tank milk variables (BTM). Data are from 8 dairy farms comprising August to October 2018, in the northwest region of Rio Grande do Sul state, Brazil. Results indicated a heterogeneous BTM composition and CB management among dairy farms, besides a strong relationship between the two sets of variables (1st pair, r(c) = 0.972; p = 0.0253). Linear combination of CB variables explained 31.2% of the BTM variation. Protein (-0.53) and total bacterial count (TBC) (0.91) were the principal variables in BTM set, while compost bedded TBC (0.51), temperature at surface (-2.28) and 20 cm depth (1.83), barn spacing per cow (-0.53), and pH value (-0.55) were the principal variables in CB set. A significant effect of CB management on BTM was found where bedding temperature should be the principal variable for monitoring.