Comportamento durante a expressão de estro de vacas holandesas de alta produção em sistema “compost barn túnel de vento”

Abstract

This study was carried out to characterize the behavior during synchronized estrus of high-producing dairy cows housed in a wind tunnel Compost Barn. Additionally, the objective was to determine which environmental, physiological, and productive variables have a greater effect on the expression of estrus in these animals. The experiment was carried out in a wind tunnel Compost Barn installation, at the José Henrique Bruschi Experimental Station, EMBRAPA – Gado de Leite, Coronel Pacheco, MG, Brazil. Thirty-five cows with 128 ±74 days in milk (DIM) and a voluntary waiting period (VWP) of 45 days were selected. Cows were placed under a fixed-time artificial insemination (FTAI) protocol based on intravaginal devices containing 1.9 g of progesterone (P4), and injection of buserelin acetate (GnRH), cloprostenol sodium, and estradiol cypionate. Auxiliary tools (electronic activity-monitoring cervical collars, video cameras, and marker sticks) were used to aid in estrus detection. The estrus behavior was observed from 24 hours after the removal of the P4 intravaginal device until the end of estrus. The environmental variables (temperature, relative humidity, temperature and humidity index - THI, wind speed, and humidity and temperature of the bedding material), physiological variables (rectal temperature - RT and respiratory rate - RR), and productive variables (milk production and DIM) were measured from the day of intravaginal device removal until the day of estrus. The duration of estrus by visual observation aided by video cameras was 12.8 ± 1.6 h, and by activity-monitoring cervical collars was 20.6 ± 3.9 h, without correlation (r = 0.12, P > 0.05) between these methods. However, considering the interval from the removal of the intravaginal P4 device to the onset of estrus, there was a correlation (r = 0.53, P < 0.05) between these two detection methods. Regarding the intensity of estrus, the behaviors more observed were mounting acceptance (37.9 ± 6.7, 22.4%), attempting to mount from behind (54.5 ± 9.3, 32.2%), and head-to-head (46.6 ± 10.6, 27.6%). As for the distribution of these three behaviors, they were mostly concentrated in the interval from 11:01 am to 5:00 pm. Regarding the physiological variables during estrus expression, RT of 38.8 ± 0.3 °C and RR of 50.4 ± 4.4 breaths per minute were found. Regarding the environmental variables during estrus expression, the ambient temperature of 18.2 ± 2.0 °C, relative humidity of 88.0 ± 1.5 %, THI of 64.0 ± 3.1, wind speed of 2.0 ± 0.1 m/s, humidity and temperature of bedding material of 50.1 ± 0.3% and 49.0 ±1.3 °C, respectively, were observed. The average milk production was 36.7 ± 7.2 liters. When applying the stepwise regression analysis, the determinant variables of estrus expression were wind speed and bedding material moisture. In conclusion, the environmental variables remained stable during the experiment, which allowed the stabilization of the physiological variables. This resulted in the duration and intensity of estrus behavior that favored its observation.