REPRODUCTIVE-PERFORMANCE OF BEEF HEIFERS - EFFECTS OF VULVO-VAGINITIS, UREAPLASMA-DIVERSUM AND PREBREEDING ANTIBIOTIC ADMINISTRATION

A group of 450 heifers, 13 to 15 mo of age, were individually identifi ed, vaccinated (IBR, PI3, Leptospira, Campylobacter fetus), examined ( body condition score, reproductive tract evaluation, assessment of vag inal lesions), and cultured for U. diversum. Heifers were randomly all ocated to either a treated group given chlortetracycline (approximatel y 350 mg/hd/d for 30 d in a grain crumble) or a nontreated control gro up. Prebreeding, most heifers showed signs of vulvovaginitis, 44% cult ured positive for U. diversum. Significant associations were found bet ween the severity of vaginal lesions and ovarian activity (P < 0.05), and between BCS and ovarian activity (P < 0.02). The U. diversum vagin al culture (positive or negative) showed no significant association wi th BCS, severity of vaginal lesions, or ovarian activity (all were P > 0.5). At pregnancy examination (35 d following conclusion of a 61-d b reeding season), treated compared with nontreated heifers showed 1) a slight but not significant (P> 0.25) decrease in vaginal colonization by U. diversum (46 to 34% and 41 to 37%, respectively); 2) an associat ion between increased severity of vaginal lesions and increasing pregn ancy rate, especially in treated heifers; and 3) an increased pregnanc y rate (72 and 57%, respectively; P< 0.01). Prebreeding treatment with chlortetracycline appeared to improve pregnancy rates in beef heifers with endemic U. diversum infections, although the role of U. diversum in heifer fertility is still not clear.