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Embryonic losses in a herd of 15-month-old aberdeen angus heifers vaccinated against foot-and-mouth disease at two different stages of gestation. case communication

Abstract:

The obligatory nature of the application of the foot and mouse disease vaccine (FMDV) for protection against this disease has, on some occasions, some contraindication with other management practices conspiring against the improvement of productive efficiency. In this aspect there are references and some research studies that indicate that the application of FMDV at certain times of the reproductive stage or the gestation stage can increase embryonic mortality. This communication presents information obtained in a non-experimental manner but which would seem to coincide with the publications mentioned above. In a commercial farm in General Viamonte, Province of Buenos Aires, for management reasons, breeding was started on Aberdeen Angus heifers on two different dates with 42 days between them (279 heifers in the first case and 174 in the second). On both occasions, a heat induction and synchronization program was applied to enable a fixed time artificial insemination (FTAI). At 33 days after the first FTAI and 10 days before the second one, FMDV was applied to all heifers (groups V+33 and V-10 respectively). The pregnancy rate at FTAI in both cases was 66.6 and 56.8% respectively (p<0.036). At 130 days after the first FTAI, a second pregnancy diagnosis was made, observing an embryonic loss rate of 16.1 and 3.0% for the V+33 and V-10 groups respectively (P <0.001). In the present study it is not possible to determine what the pregnancy rate would have been if the heifers of Group V-10 had not been vaccinated 10 days before the FTAI, so it is not possible to discern whether the pregnancy differences between the two groups was the product of the VA or another cause. What appears to be evident is that the embryonic losses in early pregnancies could be attributed to the effect of the FMDV that applied at 33 days of gestation generates large and significant differences with respect to unvaccinated animals during pregnancy. In conclusion, this study suggests that the problem of applying FMDV near the period of breeding or during early pregnancy negatively affects pregnancy rates by decreasing calving in the cows thus treated. This observation added to those of the aforementioned publications would indicate that the health authority should conduct studies on this or modify the dates of vaccination.