CRYOPRESERVATION OF RED BROCKET DEER SEMEN (MAZAMA AMERICANA): COMPARISON BETWEEN THREE EXTENDERS

Abstract

In recent years, genome banks have grown as a way of maintaining the genetic variability of populations. However, the quality of gamete cryopreservation will determine their efficiency. This study aimed to evaluate prefreeze and postthaw sperm motility, vigor, membrane integrity, and morphology of semen of red brocket deer (Mazama americana) using three extenders: E1, Tris-Yolk; E2, Tes-Tris-Yolk; and E3, Tes-Tris-Yolk-Equex. Six bucks were used, and three collections per buck were performed at 90-day intervals. Before freezing, semen volume, ejaculate concentration, motility, vigor, membrane integrity, and sperm morphology were evaluated. To compare the effect exerted by the extenders after sample thawing, further analyses of sperm motility, vigor, membrane integrity, and morphology were performed. Mean ejaculate volume and sperm concentration were 365.33 +/- 120.5 microL and 2,675.73 +/- 810.4 sperm/mL, respectively. Prefreeze motility for the extenders showed no significant differences (approximately 60%). Postthaw motility (E1 = 16.33 +/- 5.5, E2 = 5.44 +/- 5.2, E3 = 24.66 +/- 10.0) was significantly different between E2 and E3, whereas postthaw vigor (E1 =2.66 +/- 0.8, E2= 1.89 +/- 1.2, E3 = 3.83 +/- 0.4) was greater for E3 (P < or = 0.05). Analysis of postthaw membrane integrity revealed no significant differences between the extenders regarding counts of cells presenting intact membranes; however, E3 promoted the lowest number of cells with damaged membranes and higher cell counts for partially damaged membranes (P < or = 0.05). Analysis of sperm morphology revealed an increase in severe abnormalities when using E2 and E3 (P < 0.05). However, observation verified that counts of altered cells were lower using E3 than E2, suggesting a protective effect of Equex. These findings indicate that E3 promoted better semen quality postthaw. However, the performance of this extender in protecting sperm cells of M. americana during freezing was lower than that verified for other species. Thus, further studies are needed for characterization of red brocket deer semen and the optimization of extender for sperm cryopreservation.

Comparison Between Three Cryoprotectants in the Freezing of Mazama americana Semen Collected by Artificial Vagina

“…The combination of seminal collection using an artificial vagina and Regarding ejaculate volume, Rola et al 21 reported similar values to this study (130 -68 mL) for M. americana using an artificial vagina. Semen obtained by electroejaculation presents higher volume and lower concentration as observed by Rola et al, 33 with 390 -140 mL and 2.44 • 10 9 sptz/mL, and Favoretto et al, 14 with 365.33 -120.50 mL and 2.67 • 10 9 sptz/mL. The increase in volume observed in the collection performed by electroejaculation can be explained by excessive stimulation of the accessory glands, triggering a greater release of seminal plasma.…”

“…15 For M. americana, tris-citric acid with 10% yolk, tes-tris with 20% yolk, and tes-tris with 20% yolk with the addition of Equex were tested and post-thaw sperm motility was equal to 16.33%, 5.44%, and 24.66%, respectively. 14 Using the cryoprotectants GLY and DMF, we verified motility rates higher than the minimum parameter (50%) of post-thaw sperm quality stipulated for cattle. 32 In contrast, ETG was lower than this minimum parameter, which indicates that this cryoprotectant was less efficient for M. americana at the evaluated concentrations.…”

“…The semen was then equally divided into three samples, and Tris-citric acid diluent medium was added (37°C) to each of them plus one of the three cryoprotectants: 6% GLY or 3% ETG or 5% DMF, at a concentration of 2:1 (two parts of diluent to one of semen). The composition of the Tris-citric acid medium was based on previous formulations used in experiments performed on Mazama genus species 14,15 with some modifications. However, for these experiments the cryoprotectant used was always GLY.…”

“…[9][10][11] For species of the genus Mazama from neotropical regions, low post-thaw results were obtained (sperm motility around 30%), regardless of the diluent used. [12][13][14][15] For Mazama americana, the post-thaw motility ranged from 5% to 25%, depending on the diluent used (Tris-Yolk, Tes-Tris-Yolk, and Tes-Tris-Yolk Equex, all of them use glycerol [GLY] as cryoprotectant). 14 These poor results could be due to the inadequacy of the diluents and/or freezing protocols that might affect sperm characteristics in this genus.…”

“…[12][13][14][15] For Mazama americana, the post-thaw motility ranged from 5% to 25%, depending on the diluent used (Tris-Yolk, Tes-Tris-Yolk, and Tes-Tris-Yolk Equex, all of them use glycerol [GLY] as cryoprotectant). 14 These poor results could be due to the inadequacy of the diluents and/or freezing protocols that might affect sperm characteristics in this genus. 13 Penetrating cryoprotectants are among the most important components used in semen diluents and are added to lessen the harsh effects of freezing and thawing.…”