Effects of ambient air temperature, humidity, and wind speed on seminal traits in Braford and Nellore bulls at the Brazilian Pantanal

Abstract

The aim of this study was to evaluate the bioclimatic thermal stress assessed by Equivalent Temperature Index (ETI) and Temperature Humidity Index (THI) on Braford and Nellore bulls sperm quality during the reproductive seasons at the tropical region in the Brazilian Pantanal. We used 20 bulls aged approximately 24 months at the beginning of the study. Five ejaculates per animal were collected using an electroejaculator. Temperature, air humidity, and wind speed data were collected every hour from the automatic weather station at the National Institute of Meteorology. Infrared thermography images data were collected to assess the testicular temperature gradient in each animal. Data were analyzed with ANOVA using MIXED procedure of SAS and means were compared using Tukey's HSD test. The THI and ETI at 12 days (epididymal transit) were higher in January (89.7 and 28.5, respectively) and February (90.0 and 29.0, respectively) compared to other months (P < 0.01). Total seminal defects differ only in Bradford bulls between the months of November and February. Nellore bulls had lower major defects (MaD) and total defects (TD) compared to Braford. Nellore bulls showed correlation between minor defects (MiD) and THI for 30 days (0.90) and 18 days (0.88; P < 0.05). Braford bulls showed correlation for MaD (0.89) in ETI for 12 days (P < 0.05). Infrared thermography showed no difference between animals. Reproductive response to environmental changes is a consequence of Nellore and Braford adaptation to climate stress conditions. Both THI and ETI environmental indexes can be used to evaluate the morphological changes in the seminal parameters in Nellore or Braford bulls; however, more experiments should be performed focusing on larger sample numbers and also in reproductive assessment during the consecutive years to assess fertility potential.

Effect of season on scrotal circumference, semen characteristics and testosterone serum concentration in Mexican Corriente and other beef breed bulls

“…This indicates that although scrotal circumference was lower during winter and spring, the amount of sperm cells produced was not affected. European-breed bulls in the study, seemed to be more sensitive to heat stress and showed significantly lower sperm cell concentration during summer and autumn, when the mean ambient temperature reached an average of 30 o C. The negative effect of heat stress on spermatogenesis has been widely documented (Meyerhoeffer et al, 1985;Menegassi et al, 2016), and there are reports that mention that although ejaculate volume is not negatively affected by hyperthermia, initial motility, sperm concentration and total sperm counts decrease following exposure to temperatures above 29 o C and spermatogenesis is impaired at temperatures above 30 o C (Hansen, 2009). It is important to notice that semen characteristics are not immediately affected by high temperatures, and they do not return to normal until up to eight weeks following the end of heat stress (Hansen, 2009), which helps to explain the results of the lower sperm cell concentration found in European-breed bulls in the present study during the months of autumn that do not represent heat stress for the animals.…”

Infrared thermography as a noninvasive method to assess scrotal insulation on sperm production in beef bulls

“…Previously studies by our group demonstrated that IRT can be used as an indirect technique to evaluate the effect of environmental stress on bull reproductive traits based on low scrotal TG and high OcT correlation (Menegassi et al., , 2016b). In rodents, the IRT technique is a good tool to assess temperatures on eyes, nose, internal and external ear suitable for detecting differences in heat stress in rabbits (Lima et al., ).…”

“…Perhaps, thermographic image can provide a qualitative and quantitative map of the measured surface temperature that can be related to blood flow, distinct pathological conditions and reduced cellular activity (Ammer, ). Recently, it has been found that the use of IRT to evaluate environmental effects on sperm quality has a low correlation between TG and minor sperm defects that are also important for reproductive performance in bulls (Menegassi et al., 2016b). These distinctive characteristics on sperm parameters occur because the inflammatory lesions are related to changes in blood flow and this in turn can affect the scrotal skin temperature.…”

“…The IRT measurement and analysis were conducted as previously described by Menegassi et al. (, 2016b).…”

Evaluation of Scrotal Temperature in Different Testicular Shapes by Infrared Thermography in Braford Bulls

“…In the current study, the obtained THIs were considered below the temperature that impairs physiological disequilibrium due to thermal stress in animals, and thus it is likely that neither temperature nor humidity was high enough to cause testicular damage that may lead to direct consequences on testicular shape [13]. Recently, Brangus breed bulls showed a mean testicular gradient of 4.2, indicating a higher temperature gradient compared to Nelore (2.1) and Braford (3.3; 3/8 Nelore x 5/8 Hereford) bulls evaluated at the Pantanal region of Brazil [17]. The Braford breed is a mix of Bos taurus and Bos taurus indicus (3/8 Nelore x 5/8 Hereford), showing a significant adaptation to tropical and subtropical regions and presenting higher genetic potential to improve productivity efficiency.…”