This study was conducted to characterize the daily profile of testosterone secretion and its mean concentrations in the four seasons as well as to evaluate the semen characteristics and testicular biometry of Mangalarga Marchador stallions throughout the year in a tropical region. Three stallions were submitted to semen collections and evaluation of testicular biometry every 14 days along a year. Blood samples were collected once at the middle of each season, in a 20-min interval during 24 hr in order to evaluate the testosterone secretion profiles among seasons. Testosterone concentrations along the day were higher at the beginning of the afternoon (from 12:00 to 15:00 hr), but a circadian secretion was not clearly observed. Mean testosterone concentrations did not differ among seasons (p > .05), but a pattern of secretion along the day showed variations with higher concentrations in the afternoon during the winter. Ejaculate volume was higher during summer; however, sperm motility decreased in summer and spring. Total sperm in ejaculate, sperm morphology and testicular biometry kept constant along the year showing no differences among the seasons. The results demonstrated that in a tropical region, reproductive aspects of stallions did not show a clearly defined seasonal variation, and months of autumn and winter were not unsuitable for reproduction of the males.

-Thirty adult male wistar rats were used in five groups. Two groups received oral treatment with aqueous solution of TORDON 2,4-D ® 64/240 BR in different concentrations; group O1: 2 ml.L -1 (n = 6); group O2: 4 ml.L -1 (n = 6). Two groups received topical treatment in the dorsal cervical area, the following concentrations were used, group T1: 16.7 ml.L -1 (n = 6), and group T2: 400 ml.L -1 (n = 6). A control group was used without the addition of the herbicide (n = 6). At the end of the experiment, the animals were euthanized; the testes were collected and fixed for subsequent histological analysis in light microscope. The T1 group showed increase in albuginea weight (P < 0.05). The animals of the O2 group showed significant reduction (P < 0.05) of the height of seminiferous epithelium. The animals of the O1 and T2 groups did not present harmful effects on the spermatogenic morphometry.