Association of BVDV, IBRV, and Neospora caninum with late embryonic losses in a grazing dairy herd

QUINTERO RODRIGUEZ, L.E.; DOMINGUEZ, G.; ALVARADO, M.F.; TRAVERIA, G.; MORÉ, G.; CAMPERO, L.; DE LA SOTA, R.L.; MADOZ, L.V.; GIULIODORI, M.J.

Bologna

Congreso; ICAR 2020+2, 19th International Congress on Animal Reproduction; 2022

ICAR

BACKGROUND-AIMPoor embryo survival and increased pregnancy lossesare among the most important factors leading to poorreproductive performance in dairy cows. Some reportshave found that Bovine Viral Diarrhea (BVD), InfectiousBovine Rhinotracheitis (IBR) and Neospora caninum (NEO)are related to fetal loss, but, surprisingly, no study hasevaluated their association with the risk for late embryoniclosses (LEL).METHODSA prospective cohort study was carried out in an Argentiniancommercial dairy herd to identify the presence of BVD, IBRand NEO by PCR, and to assess the associations betweenseroprevalence and seroconversion to BVD, IBR and NEOwith the odds for LEL. LEL was defined as cows havingembryo with no heartbeat, or with detached membranesor floating structures including embryo remnants detectedby ultrasonography (US) at 28-42 days post-AI, whereascows with positive pregnancy by US 28-42 d post-AI wereconsidered as non-LEL. A total of 92 cows were selectedfor the study (46/group). All the cows were bled twice,at pregnancy (and LEL) diagnosis (d 0), and 28 d later.Serological diagnosis to BVD, IBR and NEO infection wasperformed on all samples and progesterone concentrationwas measured in d 0. The conceptus from LEL cows weresampled (d 0) with an insemination pistol attached to a 10mL syringe, stored in a vial with RNAlater, and transported tothe lab. Subsequently, the aspirated conceptuses from LELcows were processed for BVD, IBR and NEO identificationby PCR. The associations of risk factors (serological titers,seroconversion, and progesterone) with the odds for LELwere assessed with logistic regression models.RESULTSThe risk for LEL increased 3.44 times per 1 SD of incrementin titer to BVD over the mean at d 28 (P = 0.03), and,also, increased 3.27 times in cows that seroconverted toBVD (P = 0.09) compared with herd-mates that did not.Conversely, neither the remaining seroprevalences andseroconversions nor progesterone concentration wereassociated with the odds for LEL. Finally, only BVD viruswas identified in all the conceptuses from LEL cows thatseroconverted (9/46).CONCLUSIONSWe concluded that BVD is a risk factor for LEL in dairy cows.Conversely, IBR, NEO and progesterone concentrationseem not to play any role.