160 STRATEGIC VACCINATION AGAINST BOVINE VIRAL DIARRHEA (BVD), INFECTIOUS BOVINE RHINOTRACHEITIS (IBR) AND LEPTOSPIROSIS IMPROVES PREGNANCY RATE IN FTAI PROTOCOLS IN NELORE BEEF COWS

Abstract

The negative effect of some diseases, such as bovine viral diarrhea (BVD), infectious bovine rhinotracheitis (IBR), and Leptospirosis, on bovine reproduction rates are well known. The uses of vaccines are considered to be an important tool available in order to control reproductive losses but their efficiency is still controversial. The aim of this study was to evaluate the effects of vaccination against BVD, IBR, and Leptospirosis to improve pregnancy rate in beef cattle submitted to fixed-timed AI (FTAI). Nelore cows (n = 1172) from 4 beef cattle farms in Brazil were randomly distributed in two experimental groups: Group 1 (treated, n = 584) received the first dose of the inactivated vaccines (Bioleptogen and Bioabortogen H, Biogénesis Bagó, Garín, Argentina) at the beginning of the FTAI protocol and the second dose on the pregnancy diagnostic 40 days later; Group 2 (control group, n = 588) received 0.9% saline solution. Serum samples from 3–5% of animals in each farm herd were collected to determinate IBR, BVD, and Leptospirosis challenges, by using ELISA protocol for BVD and IBR (Synbiotics BVD p80 ab monoblocking test and Synbiotics BoHV-1 gB monoblocking test, respectively; Synbiotics Corp., Kansas City, MO, USA); and microaglutination test for Leptospirosis. All animals were submitted to the FTAI protocol: D0 = intravaginal P4 device (Cronipress, Biogenesis Bagó) and application of 2 mg oestradiol benzoate (Bioestrogen, Biogénesis Bagó); Day 8 = intravaginal device removal + 0.5 mg oestradiol cipionate (E.C.P, Zoetis Inc., Florham Park, NJ, USA) and 25 mg D-cloprostenol sodium (Croniben, Biogénesis Bagó) and FTAI after 48 h. Body condition scores (BCS) were measured on Day 0 and pregnancy diagnostic were performed on Day 40. Data were analysed by logistic regression using PROC LOGISTIC procedure of the SAS software (SAS 9.3, SAS Institute, Inc., Cary, NC, USA) as well as the significant differences between the factors was analysed to nonparametric statistical frequency (chi-square test; PROC FREQ). Pregnancy rates on day 40 were greater (P < 0.0001) in Group 1 (58.21%; 340/584) compared to Group 2 (44.73%; 263/588). Effect in BCS by pregnancy rates was observed (P = 0.0165) among animals with higher compared to lower BCS (61.40% v. 47.98%, respectively). Results from BVD, IBR and Leptospirosis prevalence were respectively (78.26%; 95.65%, and 10.20%), demonstrating that all herds were challenger for the 3 agents and a positive correlation with pregnancy rates (P < 0.001) in vaccinated group. In conclusion, vaccination with Bioabortogen H and Bioleptogen contributed to increase pregnancy rates in beef cattle submitted to FTAI; and the positive correlation between high prevalence of BVD, IBR, and leptospirosis, and an increased pregnancy rate by 13.48% can be due to fewer losses caused by the vaccination protection up to Day 40.