Testicular thermoregulation in Bos indicus, crossbred and Bos taurus bulls: relationship with scrotal, testicular vascular cone and testicular morphology, and effects on semen quality and sperm production

Brito, Leonardo F.C.; Silva, Antonio E.D.F.; Barbosa, R. T.; Kastelic, John P.

doi:10.1016/s0093-691x(03)00231-0

Cited by 154 publications

(106 citation statements)

References 18 publications

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“…Similar changes occurred at corresponding times in previous studies that involved increased testicular temperatures in bulls and rams (Howarth 1969;Meyerhoeffer et al 1985;Saab et al 2011;Rocha et al 2015;Hamilton et al 2016) with some apparent differences in the magnitude of changes and the interval from the thermal insult to recovery, attributed to the degree and duration of testicular heating and perhaps species-specific characteristics (Skinner and Louw 1966;Rathore 1970;Brito et al 2004;Nichi et al 2006). Furthermore, in this study, sperm damage occurred during the final stages of spermatogenic development in the testis (Howarth 1969;Cardoso and Queiroz 1988;Senger 2003).…”

Section: Discussionsupporting

confidence: 87%

Hyperthermia and not hypoxia may reduce sperm motility and morphology following testicular hyperthermia

Kastelic¹,

Wilde²,

Rizzoto³

et al. 2017

Vet. Med.

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ABSTRACT:The mammalian testis typically operates on the brink of hypoxia; the long-standing dogma is that increased testicular temperature increases metabolism, but blood flow is unaffected and the resulting hypoxia reduces sperm motility and morphology. In rats and mice, oxygen (O 2 ) content of inspired air affected O 2 content of testes, enabling the latter to range from approximately 50 to more than 200% of physiologic concentrations. A ram model was used to test the hypotheses that hypoxia would disrupt sperm motility and morphology and that hyperoxia would prevent hyperthermia-induced reductions in sperm motility and morphology. Eighteen Canadian Arcott rams (approximately 10 months old) were used in a 2 × 3 factorial, with factors being scrotal insulation (insulated or not insulated) and O 2 concentrations in inspired air (14, 21 or 85%). Six rams, three with and three without scrotal insulation, were placed in each of three enclosed areas for 30 h to expose them to their respective oxygen concentrations, with scrotal insulation removed at the end of the exposure. Semen was collected by electro-ejaculation twice before insulation, bi-weekly for four weeks starting one week after exposures, and then once weekly for two weeks. There were effects of insulation, time and an insulation × time interaction for motile sperm and sperm that had normal morphology or head or midpiece defects (P < 0.01 for each). Sperm motility and morphology exhibited alterations between approximately two and five weeks after insulation, with mean progressively motile and morphologically normal sperm decreasing from approximately 55 to 35% and from 80 to 30%, respectively, and with head and midpiece defects increasing from approximately 3 to 50% and from 10 to 20% (P < 0.05 for each). The hypotheses that hypoxia would disrupt sperm quality and production, whereas hyperoxia would prevent hyperthermia-induced reductions in sperm quality and production, were not supported. This is apparently the first report that heat-stress induced damage to sperm was due to increased temperature per se and not testicular hypoxia, calling into question a long-standing paradigm.

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Section: Discussionsupporting

confidence: 87%

Hyperthermia and not hypoxia may reduce sperm motility and morphology following testicular hyperthermia

Kastelic¹,

Wilde²,

Rizzoto³

et al. 2017

Vet. Med.

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“…Nellore bulls have a greater number of sweat glands in the scrotum, long, deep bodies presenting greater body surface area, thinner skin, and no scrotum hair, facilitating heat loss through convection in the environment. In addition, their greater testicular artery diameter increases blood cooling, and lower metabolic rate produces less heat (BRITO; SILVA; BARBOZA, 2004;HANSEN, 2004).…”

Section: Discussionmentioning

confidence: 99%

Efeitos da disponibilidade de sombra a campo sobre características reprodutivas de touros da raça Nelore (Bos indicus) criados na região Sudeste do Brasil

Tarragó

Rodrigues

Zaffalon

et al. 2013

Braz. J. Vet. Res. Anim. Sci.

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Solar radiation is responsible for bull body temperature elevation. An alternative to minimize heat stress is to use artificial shade. Thus, this study aimed to evaluate the effect of thermal stress reduction, through shade availability, on reproductive characteristics of Nellore bulls (Bos indicus). For this, ten bulls were divided in: Available artificial shade (AS, n = 5) and Unavailable shade (US, n = 5). Each group was kept in two hectare paddocks, in which shade availability for group AS was artificially created. Animals were submitted to a clinical-reproductive evaluation and seminal analyses. No interaction was observed between treatments (AS and US) and time (8 collections) for all analyzed variables (P>0.05). No significant effect (P > 0.05) of treatment was observed for all parameters analyzed. So, it can be concluded that the absence of shaded areas during summer does not negatively affect reproductive characteristics such as: scrotal circumference, testicular consistency, progressive motility, percentage of rapidly moving cells (Computer Assisted Semen Analysis -CASA), morphology or sperm viability in Nellore bulls raised in southeastern Brazil, considering that results could be different in other regions of the country where average temperature is higher. Keywords:Semen. Artificial shade. Nellore. Bull. ResumoA radiação solar é responsável pelo aumento da temperatura corpórea em touros. Uma alternativa para minimizar o estresse térmico é usar sombreamento artificial. Assim, este estudo teve como objetivo avaliar o efeito da redução do estresse térmico através da disponibilização de sombra artificial, sobre características reprodutivas de touros da raça Nelore (Bos indicus). Para isso, dez touros foram divididos em: Disponibilidade de sombra artificial (AS, n = 5) e Não-disponibilidade de sombra artificial (US, n=5). Cada grupo foi mantido em piquete de dois hectares cada, no qual a sombra para o grupo AS foi criada artificialmente. Os animais foram submetidos a avaliações clínicas-reprodutivas e análise seminal. Nenhuma interação foi observada entre os tratamentos (AS e US) e o tempo (8 coletas), para todas as variáveis analisadas (P > 0.05). Nenhum efeito significativo (P>0.05) de tratamento foi observado para os parâmetros analisados. Dessa forma, concluiu-se que a ausência de áreas sombreadas, durante o verão, não afetou negativamente as características reprodutivas como: circunferência escrotal, consistência testicular, motilidade progressiva, percentagem de células com movimentos rápidos (Computer Assisted Semen Analisys -CASA), morfologia e viabilidade espermática em touros da raça Nelore criados na região sudeste do Brasil, considerando que esse resultado pode ser diferente em outras regiões do país, onde as temperaturas ambientais são mais elevadas.Palavras-chave: Sêmen. Sombreamento artificial. Nelore. Touro.

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“…Adverse effects of elevated testicular temperature have been reported in the production and semen quality, reducing fertility in ruminants (BRITO et al, 2004;COULTER et al, 1988). Local mechanisms, such as countercurrent heat exchange, blood flow regulation, the position of the testes and sweating, play an important role in the maintenance of testicular temperature (BRITO et al, 2004;GABALDI;WOLF, 2002).…”

Section: Introductionmentioning

confidence: 99%

Termografia digital por infravermelho do escroto, qualidade do sêmen, níveis séricos de testosterona em touros Nelore (Bos taurus indicus) e suas correlações com os fatores climáticos

et al. 2016

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The objective was to study the relationship of climatic conditions with the temperature of the scrotum surface and sperm quality through digital infrared thermography in Nellore bulls, raised extensively. In six bulls held with scrotal thermography Flir E40® cameras, blood samples for serum testosterone and semen collection were taken by electroejaculation every 10 days, with six replications. Climatic factors: ambient temperature, relative humidity, dry globe temperature and temperature of the wet globe were recorded using a globe thermometer (InstruTemp®, ITWTG-2000). Thermal images of the scrotum were analyzed with the Flir Tools® software for the temperatures of scrotal surface, the right and left sides of the scrotum lap thirds: dorsal, middle and ventral testicles; and tails of the epididymis. The semen data and thermograms were submitted to ANOVA and Tukey's test at 5%. Pearson correlation was used for the surface temperatures of the scrotum, rectal temperature, quantitative and qualitative characteristics of semen and climatic factors. There was a positive correlation (P<0.05) for sperm motility x scrotal temperatures; sperm concentration x scrotal temperatures; climatic factors x rectal temperature. There was a negative correlation (P<0.05) between ambient temperature x sperm concentration. It was concluded that the temperature of the scrotum surface and climatic factors, temperature and humidity, influence the quality of semen. Thermography is recommended as a supplementary examination for reproductive evaluation of bulls. Key words: Climatic factors, scrotal thermogram, zebu bull, semen ResumoObjetivou-se estudar a relação dos fatores climáticos com a temperatura da superfície do escroto e qualidade seminal por meio da termografia digital de infravermelho em touros Nelore, criados extensivamente. Em seis touros realizaram-se termografia escrotal com câmera Flir E40®, colheita de sangue para a testosterona sérica e colheita de sêmen por eletroejaculação a cada 10 dias, com seis repetições. Os fatores climáticos: temperatura ambiente, umidade relativa do ar, temperatura do globo seco e temperatura do globo úmido foram registrados com globotermômetro (InstruTemp®, ITWTG-2000). Os termogramas do escroto foram analisados com o software Flir Tools® para as temperaturas da superfície escrotal, dos lados direito e esquerdo, colo do escroto, terços: dorsal, médio e ventral dos testículos; e caudas dos epidídimos. Os dados do sêmen e dos termogramas foram submetidos à análise de variância e teste de Tukey a 5%. Correlação de Pearson foi empregada para as temperaturas da superfície do escroto, temperatura retal, características quantitativas e qualitativas do sêmen e fatores climáticos. Houve correlação positiva (P<0,05) para motilidade espermática x temperaturas do escroto; concentração espermática x temperaturas do escroto; fatores climáticos x temperatura retal. Houve correlação negativa (P<0,05) entre temperatura ambiente x concentração espermática. Concluiu-se que as temperaturas da superfície do e...

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Testicular thermoregulation in Bos indicus, crossbred and Bos taurus bulls: relationship with scrotal, testicular vascular cone and testicular morphology, and effects on semen quality and sperm production

Cited by 154 publications

References 18 publications

Hyperthermia and not hypoxia may reduce sperm motility and morphology following testicular hyperthermia

Hyperthermia and not hypoxia may reduce sperm motility and morphology following testicular hyperthermia

Efeitos da disponibilidade de sombra a campo sobre características reprodutivas de touros da raça Nelore (Bos indicus) criados na região Sudeste do Brasil

Termografia digital por infravermelho do escroto, qualidade do sêmen, níveis séricos de testosterona em touros Nelore (Bos taurus indicus) e suas correlações com os fatores climáticos

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