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This study identified the association of management practices and herd characteristics with milk quality of bulk tanks in southeastern, Brazil. Milk samples were collected weekly during 8 weeks from 63 dairy herds. Bulk tanks were evaluated for total bacteria (TBC), preliminary incubation (PIC), pasteurization (PC), coliform (CC), and somatic cell counts (SCC). Associations found were type of milking system utilized in the farm with TBC, PIC, and SCC; the use of gloves for milking with TBC and PIC; sanitation of milking equipment prior to milking with PC and CC; strip cup testing of cows with PC; teat washing prior to milking with SCC; pre-milking teat disinfection with TBC and CC; post-dipping with TBC and SCC; and the alkaline-acid washing procedure of milking equipment with PIC and PC. The regression analysis explained the variation of bulk tank PC (- 0.47 log cfu/mL) due to the adoption of strip cup test (P = 0.036) and, by 0.366 log cfu/mL due to alkaline and acid washing of milking equipment (P = 0.036). Herringbone milking systems adopted on farms represented a change of - 0.11 log cfu/mL on the log SCC (P = 0.048). Findings may provide a guideline to prioritize efforts aimed at improving milk quality at the farm level in Brazil.

Staphylococcus aureus (S. aureus) is the most prevalent infectious microorganism affecting dairy cattle worldwide, and its pathogenic characteristics facilitate its spread in dairy herds. S. aureus intramammary infections (IMI) are mainly subclinical, and associated losses can exceed average herd losses where the pathogen is not isolated. However, the extent it affects milk composition at udder and quarter levels is still unknown, and cow composite milk losses may be underestimated due to the dilution effect. The aim of this study was to investigate the effects of S. aureus subclinical mastitis on mammary quarter milk yield and composition. In order to determine the effects of the pathogen on milk yield and composition at quarter level, a pairwise comparison of infected and non-infected mammary quarters (n = 28) from two dairy herds was carried out. Quarters were individually milked, and milk production and composition were assessed. S. aureus has increased somatic cell counts at quarter level; however, no effect of S. aureus IMI on milk lactose, fat, and protein contents was observed. Fat yield from infected quarters decreased, but losses due to the infection caused by S. aureus were not associated with quarter positioning in cows.