Parâmetros fisiológicos e desempenho de novilhas mestiças confinadas recebendo óleos essenciais na água de bebida

Abstract

This study aimed to evaluate the physiological parameters (rectal temperature, respiratory rate, heart rate, and surface temperature of body regions) and performance (feed efficiency, feed conversion, and average daily gain) of crossbred ½ Angus x ½ Nelore heifers kept in feedlots and receiving eucalyptus and mint essential oils diluted in drinking water. The study was previously approved by the Ethics Committee for the Use of Animals (protocol 2200038). The experiment was conducted on a rural property associated with Universidade Brasil, in the municipality of Descalvado. Twelve animals, approximately 12 months old and weighing an average of 258,21±36,84 kg, were randomly distributed in individual covered stalls measuring 12m², with individual feeders and drinkers and a concrete floor, and divided into two treatments: T1 – drinking water with the addition of eucalyptus and mint essential oils at a concentration of 0.025%; T2 – drinking water without the addition of essential oils. The adaptation to the diet and facilities lasted 14 days. The experimental period was 36 days, with weighing on days 0, 18 and 36, totaling three weighings throughout the experiment. The diets were provided twice a day, at 7:00 am and 5:00 pm, and the diets were weighed individually, as well as the leftovers, for individual control of consumption. The water in the drinkers was changed daily, and consumption was controlled by measuring the water provided and the leftovers at the end of the day. During the weighings, rectal temperature, heart rate and respiratory rate were recorded. Daily thermographic images were obtained from the animals using the nasal mirror, side, chin and forehead, at 2:00 pm, at a distance of 1.5 m. The average climatic conditions were recorded and the temperature and humidity indexes (ITU) and black globe temperature and humidity (ITGU) were estimated. Water consumption was lower in animals that received essential oils in their drinking water compared to animals in the control group (p<0.05). The parameters of dry matter consumption, live weight, feed conversion, feed efficiency and average daily gain were not affected by the supply of essential oils (p≥0.05). The surface temperature of the side region, in the fifth week of the experimental period, was lower in heifers that received essential oils. The variables of surface temperature, rectal temperature, respiratory rate and heart rate of the animals did not differ between treatments. Supplementation of eucalyptus and mint based essential oils in drinking water showed promise in reducing water consumption and modulating surface temperature in specific areas of the animals, without compromising zootechnical performance parameters.