Fatores que afetam as taxas de concepção e detecção do estro de retorno após a IATF em vacas holandesas

Abstract

The aim of this study was to evaluate the influence of season of calving, days in milk (DIM), presence of corpus luteum (CL) and season of the year at the moment of insemination on conception and estrous return detection rates of Holstein dairy cows submitted to a timed artificial insemination protocol (TAI). The protocol was: Day 0 - insert of progesterone (P4) releasing intravaginal device (CIDR®, Pfizer) and intramuscular injection of 1,0 mL of Gonadorelina (Fertagyl®, MSD); Day 7 - 2,5 mL of Dinoprost Trometamina (Lutalyse®, Pfizer) and CIDR® removal; Day 8 - 0,5 mL of Estradiol cypionate (E.C.P. ®, Pfizer); Day 10 - TAI. The pregnancy diagnosis was performed 32 days after AI by ultrasound. The cows that returned of estrous before pregnancy diagnosis were reinseminated 12 hours after estrous detection. The observation was made by trained employees twice daily, in the morning and afternoon, during 30 minutes. The cows that did not become pregnant were resynchronized using the same treatment. Data was analyzed by Logistic Regression in MINITAB program (P < 0,05). At about 406 inseminations were performed. As a result, 101 pregnancies were confirmed and 24,87% of conception and 43,27% of estrous return detection rates were found. The season of calving, the DIM and the presence of CL did not affect conception and detection rates. Season of the year did not influence conception rate, but there was an effect of this variable on detection rate, the rate found in Spring-Summer were lower than in Autumn-Winter (38,24% vs. 53,47%), which emphasizes the detrimental effect of heat stress on expression and detection of estrous in Holstein cows.