FATORES AMBIENTAIS E FISIOLÓGICOS NA TAXA DE CONCEPÇÃO DE RECEPTORAS BOVINAS DE LEITE

Abstract

The conception rate after embryo transfer in dairy cattle recipients is a determining factor for reproductive success on dairy farms. However, adverse weather conditions during the procedure are often cited as an obstacle to the effectiveness of this technique. The objective of this study was to verify whether the temperature and humidity index (THI), wind and temperature of the dairy recipient, at the time of embryo deposit in the uterine environment, influence the conception rate at 30 and 55 days of gestation, throughout the year. This study was developed based on a data survey carried out at the Samvet Embriões Laboratory, in the rural area of Morrinhos, Goiás, with dairy cattle recipients of the crossbred Holstein-Zebu breed, between March 2023 and March 2024. The data analyzed included transrectal temperature of the recipients at the time of embryo deposition. Thirty-eight recipients were evaluated, with an average age of 8.8 years and body condition score between 3.0 and 4.0, managed in an extensive system and fed with pasture, corn silage with BRS Capiaçu, concentrate and mineral salt, depending on the time of year. Pregnancy diagnosis was performed by ultrasonography at 30 days and confirmation at 55 days. Environmental conditions, such as temperature and humidity index (THI), wind speed and ambient temperature, were monitored by the Meteorological Station of the Goiano Federal Institute. Statistical analysis, by logistic regression, evaluating the influence of factors: age of the recipients, season of the year, rectal temperature, THI and wind on the conception rates at 30 and 55 days of gestation. The age of the recipients did not significantly influence conception, which were 46.42% and 32.14% in animals aged 1 to 3 years; 23.07% and 19.23% in animals aged 4 to 7 years; 29.41% and 23.52% for animals aged over 20 years at 30 and 55 days of gestation, respectively. The conception rates were 16.66% and 0.00% when the rectal temperature was below 38.0 ºC, 32.14% and 26.19% between 38.0 ºC and 39.3 ºC, and 28.57% and 14.28% above 39.3 ºC at 30 and 55 days of gestation, respectively. When the THI was below 74, the rates were 31.81% and 24.24%; between 74 and 79, 29.03% and 16.12% at 30 and 55 days of gestation, respectively. When the wind speed was below 5 km/h, the conception rates were 22.00% and 16.00%; speed between 5 and 8 km/h, 44.82% and 31.03%; and above 8 km/h, 33.33% and 33.33% at 30 and 55 days of gestation, respectively. Specifically, the age of the recipients, the THI, the season of the year, the rectal temperature and the wind did not have a significant impact on the gestational success rates in the climatic conditions described, contradicting other studies that indicate a greater influence of these parameters on the conception rates. This divergence in relation to the literature may be associated with variables not considered in this study or with particularities of the management and specific conditions of the herd analyzed. Based on the results, it can be concluded that there was no significant interference of environmental and physiological factors in the conception rate of dairy cow recipients throughout the period evaluated, in the conditions of this study.