Efeito da estacionalidade e da adição de antioxidantes em algumas características espermáticas em eqüino

Abstract

To evaluate the effect of the season in the sperm quality of the equine semen and the use of antioxidant substances in the extender before and after thawed, three experiments was performed. In the Exp. 1, in natura semen of three Mangalarga Marchador stallions, in the breeding season (BS) and not breedii station (NBS), which had been frooze in machine using comrnercial extender FR.5 (Tris-egg yolk with glicerol 5%). After thawed at 37 'C for 30 sec.. the samples had been evaluated to volume (Vo),concentration (Co), total motility (TM) and progressive motility (MP), vigor (v), acrossomal (Aci) and DNA (DNAi) integrity, in BS and NBS, as well as proteins of sperm membrane of in natura semen. The Vo and the Co at NBS were higher than BS.TM and PM in the in natura semen in the BS were higher (P<0.05) than those at NBS. On the thawed semen. there was no difference at BS and NBS. In the same way, the V at in nahrra semen was higher (P<0.05) in the samples collect at BS. After thawing, there was no significant variation and the values were lower than to those at in natura semen. The Aci analysis was similar on in natura semen at two stations. The sperm cells have intact DNA at in natura samples, on both seasons, with values similar on the thawed semen at BS and NBS. It was observed 33 spots on the in natura semen at BS and 46 spots at NBS referring to sperm membrane proteins on the semen pool of each stdlion. The 36 to 97 kDa proteins were present only at BS. It was obsewed that the spots of membrane proteins of the three stallions were concentrated between 4 and 6 iso-electric points. On the Exp. 2, it was analysed the effect of the antioxidants on the fieezing INRA82-HEPES, on stallions of different breeds classified as fertile and subfertile.It was used INRA82-HEPES without antioxidants (TI), supplemented with 120 mM of Trolox (T2) or 2 mM of Phvate (T3). The thawed samples were evaluated according to PM, membrane integrity (Mi), Aci and DNAi, membrane stability (MS) and mitochondrial membrane potential (AY). It was observed that the fertile animals had higher TM and PM in relation to the subfertile animals, independent of the antioxidant addition. To comparing the sperm parameters of the stallions, in accordance with fertiíity and antioxidant substance addition, it was observed that the phvate addition pmvided results higher (P<0.05) than those of Trolox in TM. In the Exp. 3, it was observed the use of antioxidants after semen thawing on the same stallions and freezing technique of Exp. 1. After thawing, it was used the treatments: T1= 150 pL of semen + 150 pL of Tris (Control); T2= 150 pL of semen + 150 pL of Tris + 120 p W m L of Trolox; T3= 150 pL of semen + 150 pL of Tris + 3,5 mM of Pentoxyfiline; T4= 150 pL of semen + 150 pL of Tris + 3,5 mM of Pentoxyfiline + 120 pM/rnL of Tmlox, and the samples were analyzed at 0, 60 and 120 minutes of incubation (37 "C) according to TM, PM, Aci and DNAi. Significant dserences (P~0.05)w as seen due tothe incubation time period on TM and PM at 120 min., however no difference was seen in the treatment x time incubation interaction. Based on the results we hypothethized that proteins with molecular weights between 97 and 36 kDa can be possible fertility L pointers of sperm quality; the phvate addition improve TM of fertile and sub-fertile I stallions and the Trolox addition at extender after thawing of the equine semèn preserve I the TM and PM of the sperm cells submitted to incubation (37 'C) during 120 minutes.