Epidemiology of Heifer Mastitis

Abstract

Until recently, it had been assumed that primigravid heifers were seldom affected by intramammary infections (IMI) at or near parturition. Recent research results now suggest that this assumption is false. A number of studies report a high rate of IMI in heifers at or near parturition.(1-3) Interestingly, the pathogens associated with these IMI's appear to have a regional distribution. A study in the southern United States found a high prevalence of IMI associated with Staphylococcus aureus.(2) Studies in the New England and Southeastern United States detected a high prevalence of IMI associated with coagulase negative staphylococci.(1,3) IMI's associated with Staphylococcus aureus are related to histopathologic lesions in the mammary gland which suggest that these infections may hamper the normal development of the lactating gland.(4) These findings have prompted research to investigate the use of antibiotic therapy to decrease the risk of IMI. This research has found that antibiotics administered prior to calving will decrease the prevalence of peripaturient IMI.(5,6) A question that has not been answered is: Do these infections in heifers, particularly IMI by the minor pathogens, warrant treatment? The objectives of this paper are to report preliminary data describing the incidence of IMI in heifers, the pathogens involved in the infections and the subsequent rates of clinical mastitis in first lactation heifers conditional on the IMI status at freshening.