Pantaneiro stallions: did the environment influence seminal traits and testicular biometry?

Abstract

Abstract The aim of this present study was to evaluate the testis biometry and seminal characteristicsof the Pantaneiro horse breed in two season of year. Th experiment was performed in Pantanal region of Brazil, with evaluation of seven Pantaneiro stallions aged from 4 to 12 years and raised in extensive system. Testis traits and semen of the stallions were collected during the rainy season (RS - April) and dry season (DS - October).Seminalvolume, sperm concentration, total number of spermatozoa (TNSTZ), motility, vigor, sperm major defects, sperm total defects, hypoosmotic swelling test, trypan blues test and pH were evaluated. The right and left testicular (RTL and LTL), the right and left testicular height (RTH and LTH) and the right and left testicular width (RTW and LTW) were measured and testicle volume (TV) was calculated. Statistical analysis was performed to verify the effect of season on testis biometry traits and semen traits.Correlations of all characteristics were calculated.There was effect of season on TNSTZ and sperm major defects. All others war not different between RS and DS. The testicular volume means was 179.4 ± 8.6 cm3. There was no effect of season on testicular biometry traits.High and medium correlations were observed among testis length (TL), testis width (TW), TV with TNSTZ. Motility had high correlation with hypoosmotic test. High magnitude correlation was also observed between hypoosmotic test and intact membrane on trypan blue test. It suggests that the integrity of the membrane is essential for a good function of the kinetic of the spermatozoa.The results showed that the Pantaneiro stallions is adapted to the specific tropical environment and not presenting reproductive seasonality, being able to have your semen collected during the entire year without affect its quality also without testicular variation. Furthermore,the testicular length, width and testis volume showed highly representative as a criterion to selection of Pantaneiro stallions to reproduction.