Comparison of estradiol benzoate doses for resynchronization of ovulation at 14 days after timed-AI in suckled beef cows

Author(s)

da Silva, Amanda Guimaraes ; Nishimura, Thiago Kan ; Rocha, Cecilia Constantino ; Motta, Igor Garcia ; Neto, Adomar Laurindo ; Ferraz, Priscila Assis ; Bruni, Gabriela Andrade ; Orlandi, Raphael Evangelista ; Martinelli Massoneto, Joao Paulo ; Pugliesi, Guilherme

• Document type: Journal article
• Source: Theriogenology; v. 184, p. 10-pg., 2022-03-08.

Abstract

We aimed to compare the effects of use of 1 or 2 mg estradiol benzoate (EB) associated with an intravaginal progesterone (P4) device for resynchronization of ovulation 14 days after timed-AI (TAI) in suckled beef cows. Nelore cows were submitted to a TAI (DO) and on D14, received an intravaginal P4 device and were randomly assigned to EB-1 group [n = 516] or EB-2 group [n = 510], which that received 1 or 2 mg EB, respectively. Also, cows had the ovaries scanned by ultrasound to detect an active CL on D14. On D22, devices were removed and structural luteolysis was detected by color-Doppler ultrasonography. In cows which underwent luteolysis, the resynchronization protocol was continued and they were submitted to second TAI on D24. Pregnancy diagnosis was performed 30-35 days after first or second TAI. A subgroup [n =18-19/group] was submitted to daily ovarian ultrasound scanning from D14 to D22. Proportion of cows with an active CL on D14 did not differ (P > 0.1) between EB-1 and EB-2 groups. The proportion of cows with an active CL on D22 and pregnancy per AI (P/AI) at first TAI were greater (P <= 0.05) in EB-1 (55% and 51%) than in EB-2 group (48% and 42%). The P/AI at second TAI did not differ (P> 0.1) between EB-1 (47% [106/227]) and EB-2 group (42% [110/259]). Cumulative pregnancy rate was greater in EB-1 (73% [370/508]) than in EB-2 group (64% [322/502]). No difference (P > 0.1) was observed in the proportion of non-pregnant cows with a synchronized follicular wave emergence between EB-1 and EB-2 groups. In conclusion, treatment with either 1 or 2 mg EB associated with an intravaginal P4 device at D14 after TAI are efficient to synchronize a new follicular wave emergence. The decreased P/AI from first TAI observed in the group of cows receiving 2 mg indicates that this dose is not recommended for use in resynchronization programs initiated 14 days after TAI. The use of 1 mg EB associated with a P4 device provides an elevated cumulative pregnancy rate after two TAIs with an interval of 24 days. (C) 2022 Published by Elsevier Inc. (AU)

• FAPESP's process: 19/07805-0 - Use of different doses of estradiol benzoate in synchronization and resynchronization at 14 days after FTAI in Bos indicus beef cows
• Grantee: Amanda Guimarães da Silva
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 15/10606-9 - Innovations in the early pregnancy diagnosis in cattle
• Grantee: Guilherme Pugliesi
• Support Opportunities: Research Grants - Young Investigators Grants