Abstract: This study was conducted to compare systemic versus intramammary administration of antibiotics in eliminating intramammary infection (IMI) of Staph. aureus in Holstein heifers. Heifers approaching parturition were randomly assigned into 4 groups of 30. Group 1 to 3 received Nafpenzal-DC (DC), Tylosin (TY), Enrofloxacin(EN), respectively and group 4 received no treatment (control). Postpartum cure rates were 93, 83, 70 and 47% in
heifers of Group 1 to 4, respectively (p<0.05). The cure rates in heifers that belonged to DC and TY groups were higher than that in control group (p<0.01). There was no significant difference between the cure rates of TY and DC groups and between EN and TY groups. Cure rate in DC group was greater than that in EN group (p<0.05). In conclusion, prepartum systemic treatment by Tylosin, which is easier to apply and prevents injuries for both heifer
and milker, might replace DC treatment for controlling staphylococcal mastitis in dairy heifers. J.Vet.Res. 62,2:7-9,2007.