Resposta termorregulatória da capsaicina em cordeiros terminados em diferentes sistemas produtivos

Abstract

Several sheep breeds are adapted to heat, although these animals can still suffer from heat stress in challenging climatic conditions. In this sense, the search for alternatives to mitigate this problem is becoming increasingly relevant. Thus, the objective of this study was to evaluate wheter the inclusion of capsaicin in the diet affects the thermoregulatory response of lambs finished in different pasture-based systems. The experiment was conducted at the Sheep and Goat Teaching and Research Unit of the Federal University of Technology - Paraná, Campus Dois Vizinhos/PR, during the summer (december to april 2023), in an area divided into six paddocks. Both systems were composed of Megathyrsus maximus Jacq. cv. Aruana. A total of 21 lambs (13 intact males and 8 females), crossbred Dorper x Santa Inês, with an average weight of 36.0±1.8 kg, age of 6.0±1.0 months, and a body condition score of 3.0±0.5 were used. The treatments evaluated were: lambs in a full sun system with capsaicin supplementation (CSC-PS); animals in a full sun system without capsaicin supplementation (SSC-PS); lambs in a silvopastoral system with capsaicin supplementation (CSC-SSP); and animals in a silvopastoral system without capsaicin supplementation (SSC-SSP). All lambs were supplemented with concentrate (1.5% of body weight), and the treatments with capsaicin addition received 300 mg/day of CAPSIN®. Microclimatic variables of both systems and physiological parameters of the lambs were evaluated. The experiment used a randomized block design with a 2 x 2 factorial arrangement (shade and capsaicin), and the data were analyzed using mixed models. Analysis of variance and Type III F-tests were applied, and Tukey's test was used to verify significant differences (P < 0.05), using R software. The silvopastoral system provided a better microclimate for the animals, with temperatures approximately 3 °C lower (PS = 47 °C; SSP = 44.3 °C) and relative humidity about 2% higher than the full sun system (PS = 66%; SSP = 64%). The addition of capsaicin to the diet showed improvements in thermoregulatory control, preventing the animals from reaching their thermoregulatory limits. Lambs supplemented with capsaicin had lower respiratory rate than those not supplemented (With capsaicin= 124 and Control= 130 beats/minute), which also occurred for heart rate (With capsaicin= 115 and Control= 120 beats/minute), indicating more efficient thermoregulatory control. In the silvopastoral system, animals showed lower respiratory and heart rates and lower surface temperatures compared to the full sun system (33.3 °C and 37.6 °C, respectively). Regarding rectal temperature, all treatments remained within the standard range for the species. As for animal performance, there was no statistical difference between treatments. Therefore, it is concluded that the use of capsaicin helped in the thermoregulatory control of lambs, reducing respiratory rates during thermal stress, but did not improve zootechnical performance. The silvopastoral system provided a more favorable microclimate, with lower temperatures and higher relative humidity, enhancing thermal comfort.