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

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.

The uses of infrared thermography to evaluate the effects of climatic variables in bull's reproduction.

The objective of this study was to evaluate the seasonal effects of the environment on sperm quality in subtropical region determined by temperature and humidity index (THI). We used 20 Brangus bulls (5/8 Angus × 3/8 Nellore) aged approximately 24 months at the beginning of the study. Semen evaluations were performed twice per season during 1 year. Climate THI data were collected from an automatic weather station from the National Institute of Meteorology. Infrared thermography images were used to determine the temperature of the proximal and distal poles of the testis to assess the testicular temperature gradient (TG). The seasonal effects on seminal and climatic variables were analyzed with ANOVA using MIXED procedure of SAS. Sperm motility in spring (60.1%), summer (57.6%), and autumn (64.5%) showed difference compared to winter (73.0%; P < 0.01). TG was negatively correlated with THI at 18 days (spermiogenesis) (-0.76; P < 0.05) and at 12 days (epididymal transit) (-0.85; P < 0.01). Ocular temperature (OcT) had a positive correlation with THI at 18 days (0.78; P < 0.05) and at 12 days (0.84; P < 0.01). Motility showed a negative correlation with THI only at 18 days (-0.79; P < 0.05). During spermiogenesis, the TG had higher negative correlation compared to OcT (-0.97; P < 0.01) and rectal temperature (-0.72; P < 0.05). Spermatozoa with distal midpiece reflex were correlated with THI during transit epididymis (0.72; P < 0.05). Seminal parameters are not affected when THI reaches 93.0 (spermiogenesis) and 88.0 (epididymal transit). We concluded that infrared thermography can be adopted as an indirect method in order to assess the effect of environmental changes in TG and OcT of Brangus bulls.