Climatic seasons and time of the day influence thermoregulation and testicular hemodynamics in Santa Inês rams raised under humid tropical conditions

Juliana Nascimento Duarte Rodrigues; José Domingos Guimarães; Jeferson Ferreira Fonseca; Jurandy Mauro Penitente-Filho; Paulo Sergio Cerqueira Rangel; Camilo José Ramírez López; Rafael Souza Freitas; Erick Fonseca de Castilho; Luiz Fernando de Souza Rodrigues; Maria Emilia Franco Oliveira; Alexandre Rossetto Garcia

doi:10.1016/j.jtherbio.2023.103546

Climatic seasons and time of the day influence thermoregulation and testicular hemodynamics in Santa Inês rams raised under humid tropical conditions

J Therm Biol. 2023 May:114:103546. doi: 10.1016/j.jtherbio.2023.103546. Epub 2023 Apr 5.

Affiliations

¹ Department of Veterinary Medicine, Federal University of Viçosa, Av. Peter Henry Rolfs, s/n, 36570-000, Viçosa, MG, Brazil.
² Embrapa Goats and Sheep, Estrada Sobral/Groaíras, km 04, PO Box 145, 62010-970, Sobral, CE, Brazil.
³ Institute of Animal Health and Production, Federal Rural University of Amazon, Avenida Presidente Tancredo Neves, 2501, 66077-830, Belém, PA, Brazil.
⁴ Embrapa Goats and Sheep, Estrada Sobral/Groaíras, km 04, PO Box 145, 62010-970, Sobral, CE, Brazil; Department of Pathology, Reproduction and One Health, School of Agricultural and Veterinarian Sciences, São Paulo State University, Via de Acesso Prof. Paulo Donato Castellane, s/n, 14884-900, Jaboticabal, SP, Brazil.
⁵ Animal Reproduction Biotechnology Laboratory, Embrapa Southeast Livestock, Rod Washington Luiz, km 234, 13560-970, São Carlos, SP, Brazil. Electronic address: alexandre.garcia@embrapa.br.

PMID: 37344020
DOI: 10.1016/j.jtherbio.2023.103546

Abstract

This study evaluated the possible association between the diurnal variations of climatic factors during the rainy (RS) or less rainy (LS) seasons on the testicular hemodynamics and thermoregulatory responses of hair sheep rams raised in a humid tropical climate. Santa Inês rams (n = 6) underwent evaluation of general and testicular physiological parameters (heart and respiratory rates, internal and scrotal temperatures, internal-scrotal temperature gradient, scrotal distention, and color Doppler ultrasound evaluation of the spermatic cords and spectral analyses of testicular arteries) over six consecutive weeks per season at three separate times daily (morning = 8:00 a.m., noon = 12:00 p.m., and afternoon = 5:00 p.m.) during the RS and LS. Climatic air temperature and relative humidity data were recorded, and the temperature and humidity index (THI) was calculated. Higher thermal challenge was observed in LS relative to RS (air temperature = 28.0 vs. 30.9 °C; relative humidity = 84.1 vs. 69.9%; THI = 80.0 vs. 82.5; P < 0.05). In both seasons, respiratory rate and internal temperature were normal, demonstrating the animals' adaptability. In RS, however, a higher scrotal temperature was recorded in relation to LS (35.0 vs. 34.7 °C; P < 0.05), with a gradual increase from morning to afternoon. Lower resistivity (0.40 vs. 0.64; P < 0.05) and pulsatility (0.55 vs. 1.14; P < 0.05) indices, and a higher rate of high-velocity blood flow of testicular arteries (71.1 vs. 60.6%; P < 0.05) were observed in RS compared to LS. The lowest correlations between testicular hemodynamic, physiological variables, and environmental parameters (P < 0.05) were observed in the morning. In conclusion, testicular thermoregulation and testicular hemodynamics were influenced by the climatic seasons and time of the day, being more efficient in the LS season and with less interference from environmental factors in the morning.

Keywords: Doppler ultrasound; Hair sheep; Spermatic cord; Testicular thermoregulation.

MeSH terms

Animals
Body Temperature Regulation
Hemodynamics
Male
Seasons
Sheep
Sheep, Domestic / physiology
Testis* / physiology
Tropical Climate*