RESUMEN
We evaluated if an additional GnRH injection 7 days before pre-synchronization with simultaneous PGF2α and GnRH (PG+G) would improve responses to presynchronization, synchronization, and pregnancy per AI (P/AI). We hypothesized that administering GnRH 7 days before PG+G would increase ovulation and corpus luteum (CL) presence at the PG+G, improve response to OvSynch treatments and P/AI. Holstein cows were blocked by parity and randomly assigned to either a PG+G (Control, n = 205); or to GnRH followed 7 days later by PG+G (ExtG, n = 201). At enrollment, Control was left untreated, whereas ExtG received GnRH. Seven days after enrollment, Control and ExtG received PG+G followed by OvSynch 7 days later (GnRH, 7 days PGF2α, 56 h GnRH, 16 h timed AI). Ovarian dynamics were assessed using ultrasonography in a subset of cows (n = 53 for Control; and n = 50 for ExtG) at each treatment, except the 2nd GnRH of OvSynch. Pregnancy diagnosed at 32- and 67-days post AI. Ovulation at enrollment tended (P = 0.06) to be higher for ExtG, but ovulation was not different at PG+G (P = 0.41) and first GnRH of the OvSynch (P = 0.25). There was a tendency (P = 0.08) for ExtG to have larger CL than Control at PGF2α of the OvSynch. There were no differences in CL and follicle sizes in any other treatment point assessed. There were no differences (P = 0.12) in luteolysis between treatments after PG+G. Overall P/AI was similar between treatments on Day 32 (Control = 33.0% vs. ExtG = 34.6%, P = 0.75) and 67 (Control = 31.8% vs. ExtG = 32.5%, P = 0.29) post AI. There was a tendency for an interaction between treatment and parity (P = 0.09) for P/AI at day 67 post-AI. In multiparous cows, ExtG tended to have greater P/AI than Control, whereas, in primiparous cows Control tended to have greater P/AI than ExtG at day 67 post-AI. In conclusion, the effects of GnRH 7 days before PG+G presynchronization lead to positive and negative tendencies, respectively, in multiparous and primiparous cows for P/AI at day 67 post-AI and needs further investigation.
RESUMEN
OBJECTIVE: To describe the clinical manifestation of epizootic hemorrhagic disease virus (EHDV) in cattle during an outbreak in northwestern Illinois in the fall of 2013. DESIGN: Outbreak survey. SAMPLE: 18 EHDV-affected cattle herds. PROCEDURES: Herds with confirmed EHDV-infected cattle were selected for the survey on the basis of having a manager willing to participate. A survey was developed and administered to obtain information regarding the demographics of EHDV-affected herds and the clinical signs and outcomes for EHDV-infected cattle. RESULTS: The managers of 13 beef and 5 dairy herds participated in the survey. The herds contained approximately 1,400 cattle, of which 61 were infected with EHDV and 16 died. Most cattle clinically affected with EHDV were adults, although 1 herd had 6 calves with clinical signs, and EHDV was identified during postmortem testing of 1 of those calves. Clinical signs most commonly observed were oral ulcerations or erosions, anorexia, weight loss, and lameness that typically lasted > 7 days. Of the 18 herds, 17 had wooded areas and 14 had at least 1 pond or marsh on the property. Deer were observed on the property of all farms. The EHDV outbreak in cattle coincided with an EHDV outbreak in deer in the region. CONCLUSIONS AND CLINICAL RELEVANCE: This large-scale outbreak of EHDV in US cattle was unusual because calves were affected. Because there is no way to effectively predict or prevent an EHDV outbreak in cattle, development of a vaccine for use in cattle during an outbreak would be beneficial.
