Staphylococcus aureus intramammary infection affects milk yield and SCC of dairy cows
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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.
KeywordsSubclinical mastitis Quarter milk sample Milk losses Mastitis pathogen
This project was supported by São Paulo Research Foundation (FAPESP), Brazil (grant no. 2007/08577-3). Bruno Garcia Botaro received a scholarship (grant no. 2008/05077-3) from FAPESP during the development of this project. Authors acknowledge Lucinéia Mestieri and José Franchini Garcia Moreno, from the Department of Animal Production and Nutrition, and Dr. Priscilla Anne Melville, from the Department of Preventive Veterinary Medicine and Animal Health, School of Veterinary Medicine and Animal Sciences of the University of São Paulo, Brazil, and also Dr. Fredi Alexander Díaz Quijano, from the Department of Epidemiology, School of Public Health of the University of São Paulo, Brazil, for their technical assistance.
Conflict of interest
The authors declare that there is no conflict of interest among the authors and other people or organizations that could inappropriately bias their work.
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