Effect of access to natural shade on scrotal thermoregulatory capacity, integrity of the testicular parenchyma and sperm morphology of Nelore (<italic>Bos indicus</italic>) and Canchim (<italic>Bos taurus</italic> x <italic>Bos indicus</italic>) bulls.

The objective of this work was to evaluate the effect of using naturally shaded pastures on scrotal thermoregulatory capacity, testicular echotexture, and sperm morphology of Nelore (<italic>Bos indicus</italic>) and Canchim (5/8 <italic>Bos taurus</italic> x 3/8 <italic>Bos indicus</italic>) bulls in a tropical climate region. Sixty-four adult Nelore and Canchim bulls were used, equally allocated in Full Sun (FS, <italic>n</italic> = 32) or Crop-Livestock-Forestry (CLF, <italic>n</italic> = 32) pasture systems. During five consecutive climate seasons, the bulls underwent monthly breeding soundness evaluations and the biometeorological variables in the systems were continuously monitored. Microclimate was significantly different between systems. CLF system had lower BGHI than FS throughout the experimental period. No triple interaction (Season x Breed x Treatment, <italic>P</italic> > 0.05) was observed for any of the variables. Animals in CLF showed lower body temperature in Summer (FS:39.41 ± 0.05 vs. CLF:39.30 ± 0.05 °C; <italic>P</italic> = 0.005) and in Autumn (FS:39.54 ± 0.05 vs. CLF:39.35 ± 0.05 °C; <italic>P</italic> = 0.005). Access to shading did not determine differences in the evolution of scrotal biometry, temperatures, and scrotal thermal gradients (<italic>P</italic> > 0.05). Regardless of breed, animals in CLF showed greater right testicular volume (FS:247.5 ± 5.7 vs. CLF:259.0 ± 5.7 cm³; <italic>P</italic> < 0.05), more suitable parenchyma echotexture, and fewer microlithiasis spots in the Spring and Summer. Testosterone concentration was higher in FS (FS:2.6 ± 0.2 vs. CLF:2.1 ± 0.2 ng/mL; <italic>P</italic> = 0.035). Canchim bulls presented higher total sperm defects during the Autumn and Winter (<italic>P</italic> = 0.010), but the total defects levels for Canchim and Nelore bulls were in normal range for adult bulls. Thus, the natural shade in CLF system was effective in improving the microclimate of pastures and minimizing adverse environmental effects on some reproductive features of interest in beef cattle. [ABSTRACT FROM AUTHOR]