Influências da condição corporal e atividade ovariana sobre a taxa de prenhez de vacas de corte suplementadas com progesterona de longa ação após a IATF

Abstract

Embryo loss commonly occurs in the first three weeks after insemination due to low progesterone (P4) concentrations. Therefore, this study evaluates the effects of body condition score (BCS) and ovarian condition (OC) on pregnancy rates (P/AI) in beef cows supplemented with long-acting P4 after timed artificial insemination (TAI). We used 1573 lactating Nellore cows at 30-60 days postpartum. The animals were presynchronized on Day-10 and inseminated on Day 0. On Day 4, they were evaluated for BCS, OC and parturition order and divided into two treatment groups: P4 supplementation (N= 786) and control group (N = 787). Ultrasound exams were performed on Days-10 and 0 to measure follicle diameter and on Day 4 to evaluate corpus luteum (CL) area. BCS was determined on Day-10. P/AI did not vary between P4 supplementation and control treatments (P = 0.49). Cows with BCS > 2.75 had better P/AI than cows with BCS ≤ 2.5 (P < 0.05). Cows without CL and with follicle diameter ≥ 8 mm on Day-10 presented better P/AI than cows with follicle < 8 mm or CL (P < 0.05). In conclusion, P4 supplementation after TAI did not improve P/AI. However, BCS and OC affected P/AI and the animals with better BCS at the beginning of the experiment had better OC and P/AI.