IMPACTO DO CICLO REPRODUTIVO, DA ORDEM DE PARTO E DO ESCORE DE CONDIÇÃO CORPORAL NA TAXA DE PRENHEZ DE VACAS NELORE SUBMETIDAS A IATF

Abstract

The aim of this study was to evaluate the influence of body condition score (BCS) on pregnancy rate in Nellore cows submitted to fixed-time artificial insemination (FTAI) in an extensive cow–calf system at Arara Azul Farm, located in Natividade, Tocantins, Brazil. Zootechnical and reproductive records from the 2022/2023 and 2023/2024 reproductive cycles were used, combined with on-farm observations of nutritional, health, and reproductive management. Data were organized in spreadsheets containing individual cow information and consolidated reports of the reproductive program (FTAI, pregnancy diagnoses, and bull exposure). The protocol included an intravaginal progesterone device and estradiol benzoate on Day 0, device removal with hormone applications on Day 8, and FTAI on Day 10, followed by bull exposure. No significant interaction was observed between reproductive cycle and parity, and neither factor affected pregnancy rate after the first FTAI; however, reproductive cycle affected pregnancy rate after bull exposure. An interaction between reproductive cycle and BCS was detected for final pregnancy rate, with higher performance at intermediate–high BCS in 2022/2023 and a more uniform pregnancy distribution in 2023/2024, especially at lower scores, suggesting effects of improved management and forage availability. It is concluded that BCS is a key indicator of reproductive efficiency and that nutritional and management adjustments favor higher final pregnancy rates in extensive systems.