title: Daily rhythmicity of the thermoregulatory responses of locally adapted Brazilian sheep in a semiarid environment.
abstract: The goal of this study was to evaluate the daily rhythmicity of the thermoregulatory responses of Morada Nova ewes that were raised in a semiarid environment. The experiment was conducted during the dry season. Data were collected from 5:00 a.m. to 4:00 a.m.. Samples were taken over the course of 8 days, with a 1-week interval between sampling periods. During each day that the data were collected, animals were measured once an hour for 24 h in an area directly exposed to solar radiation. The environment was characterized by measuring the following variables: air temperature (TA), relative humidity (RH), Black Globe Humidity Index (BGHI), radiant heat load (RHL), and wind speed (WS). Physiological variables that were measured included rectal temperature (RT, °C), respiratory rate (RR, breaths/min), surface temperature (ST, °C), and sweating rate (SR, g m2h-1). We observed that RT, RR, and ST increased as environmental conditions became more stressful. Specifically, environmental conditions became more stressful as RHL, air temperature, and BGHI increased, while RH decreased. All physiological variables of the animals were strongly affected by the time of the day: environmental variables changed drastically between nighttime and noon. Physiological parameters increased sharply from the morning (7:00 a.m.-10:00 a.m.) until noon (11:00 a.m.-2:00 p.m.), except for sweating rate. After noon, these variables began to drop until nighttime (11:00 p.m.-6:00 am), and values of the main physiological indexes were stable during this period. The Morada Nova breed exhibited daily cyclic variations in thermoregulatory responses. Evaporative heat loss mechanisms were triggered during the most stressful times of the day. The first mechanism that animals used was panting, which was an immediate response to environmental heat stress. Cutaneous evaporation had a slower response mechanism to environmental heat stress. Homeothermy conditions were restored to the animals at approximately 5:00 p.m.; however, these findings confirm the importance of providing environmental protection during critical periods of the day, even for locally adapted breeds. These responses suggest that the use of thermal storage allowed the animals to achieve equilibrium with the environment and maintain a stable body temperature.
authors.affiliation: Department of Animal Science, Universidade Federal Rural do Semiárido, Francisco Mota Avenue, 572, district Costa e Silva, Mossoró, RN, 59625-900, Brazil. Wilma_manu1@hotmail.com.
authors.forename: Wilma Emanuela
authors.initials: WE
authors.lastname: da Silva
authors.affiliation: Department of Animal Science, Universidade Federal Rural do Semiárido, Francisco Mota Avenue, 572, district Costa e Silva, Mossoró, RN, 59625-900, Brazil.
authors.forename: Jacinara Hody Gurgel Morais
authors.initials: JHGM
authors.lastname: Leite
authors.affiliation: Department of Animal Science, Universidade Federal Rural do Semiárido, Francisco Mota Avenue, 572, district Costa e Silva, Mossoró, RN, 59625-900, Brazil.
authors.forename: José Ernandes Rufino
authors.initials: JER
authors.lastname: de Sousa
authors.affiliation: Department of Animal Science, Universidade Federal Rural do Semiárido, Francisco Mota Avenue, 572, district Costa e Silva, Mossoró, RN, 59625-900, Brazil.
authors.forename: Wirton Peixoto
authors.initials: WP
authors.lastname: Costa
authors.affiliation: Department of Animal Science, Universidade Federal Rural do Semiárido, Francisco Mota Avenue, 572, district Costa e Silva, Mossoró, RN, 59625-900, Brazil.
authors.forename: Wallace Sostene Tavares
authors.initials: WST
authors.lastname: da Silva
authors.affiliation: Department of Science Universidade Federal do Rio Grande do Norte, RN 160, KM 03, Macaíba, RN, 59280-000, Brazil.
authors.forename: Magda Maria
authors.initials: MM
authors.lastname: Guilhermino
authors.affiliation: Department of Science Universidad de La Laguna, Carretera General do Geneto, 2, 38071, San Cristobal de La Laguna, Santa Cruz de Tenerife, Canary Islands, Spain.
authors.forename: Luis Alberto Bermejo
authors.initials: LAB
authors.lastname: Asensio
authors.affiliation: Department of Animal Science, Universidade Federal Rural do Semiárido, Francisco Mota Avenue, 572, district Costa e Silva, Mossoró, RN, 59625-900, Brazil.
authors.forename: Débora Andréa Evangelista
authors.initials: DAE
authors.lastname: Façanha
mesh_terms: D000818:Animals; D001831:Body Temperature; D001833:Body Temperature Regulation; D001938:Brazil; D002980:Climate; D005260:Female; D010507:Periodicity; D056152:Respiratory Rate; D012756:Sheep / Q000502:physiology*; D014887:Weather
keywords: Adaptation; Respiratory rate; Sweating rate