SURVEY OF INTRAMAMMARY INFECTIONS IN DAIRY HEIFERS AT BREEDING AGE AND FIRST PARTURITION

A survey was conducted to determine and contrast prevalence of IMI in nulligravid and primigravid dairy heifers pre- and postpartum. Contras ts were made to evaluate the risk factors of location of dairy, trimes ter of gestation, and season of sampling on IMI. Twenty-eight dairies in California, Louisiana, Vermont, and Washington were studied. Lactea l secretions were collected aseptically from heifers at breeding age ( 8 to 19 mo) from one side of the gland and again at 4 d postpartum fro m all quarters. Of the quarters sampled, 65.6% prepartum and 64.0% pos tpartum were free of IMI. The percentages of quarters with IMI from co agulase-negative staphylococci or Staphylococcus aureus IMI were 27.1 and 9% prepartum and 21.8 and 2.9% postpartum. Staphylococcus aureus I MI were most prevalent in Louisiana during the months other than summe r. Location, herd, and season significantly influenced prevalence of I MI. The prevalence of IMI was greatest during the last trimester of pr egnancy, ranging from 49.2% in the winter to 36.8% in the summer. The significant effects of herd location and season suggest that managemen t variables influence prevalence of heifer IMI. Because prevalence of IMI was greatest during the last trimester of pregnancy compared with prevalence during earlier-stages of pregnancy, the heifer may be most susceptible to this disease during this period of first gestation.