Reproductive efficiency in Bos indicus and Bos indicus crossed: impact of timed artificial insemination (TAI) using a progesterone and estradiol benzoate-based protocol

Abstract

ABSTRACT Data from 15,342 bovine females subjected to timed artificial insemination (TAI) were analysed with the objective of assessing the pregnancy rate (PR) and its association with breed, number of uses of intravaginal implant, body condition score (BCS), animal categories, number of AI, and estrus expression before TAI. The protocol involved administering intravaginal progesterone + estradiol benzoate (day zero), progesterone removal + prostaglandin F2α+estradiol cypionate + equine chorionic gonadotropin (day 8) and TAI + gonadotropin-releasing hormone (day 10) in animals without estrus. Crossbred cows demonstrated higher PR. Non-suckling cows, those with 1st – and 2nd-use implants, and a single-dose implant demonstrated higher PR between categories; the BCS (>2.75–3.5) resulted in better overall PR. There were no differences in the general PR between number of AI. 2nd-use implants resulted in a better overall PR. Primiparous cows resulted better PR with 3rd-use implants. Animals in estrus before TAI demonstrated a higher PR. In conclusion, this study observed no significant differences in general PR among number of AI. Second-use implants were effective. Crossed and non-suckling cows, and 1st – and 2nd-use and single-dose implants exhibited higher fertility. Estrus before TAI favoured PR.