| Popis: |
A group of 450 heifers, 13 to 15 mo of age, were individually identified, vaccinated (IBR, PI(3), Leptospira, Campylobacter fetus), examined (body condition score, reproductive tract evaluation, assessment of vaginal lesions), and cultured for U. diversum . Heifers were randomly allocated to either a treated group given chlortetracycline (approximately 350 mg/hd/d for 30 d in a grain crumble) or a nontreated control group. Prebreeding, most heifers showed signs of vulvovaginitis, 44% cultured positive for U. diversum . Significant associations were found between the severity of vaginal lesions and ovarian activity (P0.05), and between BCS and ovarian activity (P0.02). The U. diversum vaginal culture (positive or negative) showed no significant association with BCS, severity of vaginal lesions, or ovarian activity (all were P0.5). At pregnancy examination (35 d following conclusion of a 61-d breeding season), treated compared with nontreated heifers showed 1) a slight but not significant (P0.25) decrease in vaginal colonization by U. diversum (46 to 34% and 41 to 37%, respectively); 2) an association between increased severity of vaginal lesions and increasing pregnancy rate, especially in treated heifers; and 3) an increased pregnancy rate (72 and 57%, respectively; P0.01). 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. |
