Abstract
The objective of this study was to evaluate the effects of the addition of different concentrations of ozone to quarter horse semen submitted to cryopreservation. Six ejaculates from four stallions were collected and were divided in four experimental groups: a control group (BotuCRIO® extender) and three other groups with BotuCRIO® ozonized at concentrations of 6, 8 and 12 μg of O3/mL. The semen samples were diluted (200 x 106 spermatozoa/mL), filled in straws and frozen. After thawing (37 ºC, 30s), the samples were evaluated at 0, 30 and 60 minutes of incubation regarding sperm kinetics by a computer-assisted sperm analysis (CASA), and plasma membrane integrity (PMI), acrosome integrity (ACi) and mitochondrial membrane potential (MMP) by fluorescent probes. There was a reduction in the kinetic parameters total motility (TM), progressive motility (PM), curvilinear velocity (VCL), straight line velocity (VSL) and average path velocity (VAP) in all groups during the thermoresistance test (TT), a pattern also found in PMI and MMP analyses (p<0.05). There was no difference (p>0.05) between the control and treatment (6, 8, and 12 μg of O3/mL) groups, in any of the evaluated times for the kinetic parameters TM, linearity (LIN), straightness (STR), wobble index (WOB), amplitude of lateral head displacement (ALH) and beat cross frequency (BCF). Regarding the VCL, VSL and VAP parameters, the group treated with 6 μg did not differ from the control or from 8 μg, but was higher than 12 μg at 30 and 60 minutes. ACi and PMI did not differ between groups (p>0.05), but PMI was lower in groups 8 μg and 12 μg compared to the control and 6 μg (p<0.05). It was concluded that the addition of ozone does not present beneficial effects for cryopreservation of equine semen at the concentrations used and decreases important parameters of fertility.
Highlights
The cryopreservation of semen represents an important resource in the preservation of the equine species, both by the attempt to maximize fertility and by the use of genetically superior stallions
Considering the need to minimize the deleterious effects caused by freezing/thawing of equine sperm, and the applicability of ozone therapy in veterinary medicine in order to stimulate a possible antioxidant response to the oxidative processes promoted by cryopreservation, the objective of the present study was to evaluate the addition of O3 to equine semen extender and its effect on sperm cell viability
Considering the absence of individual effect (p> 0.1), the ejaculates were grouped according to the experimental treatments
Summary
The cryopreservation of semen represents an important resource in the preservation of the equine species, both by the attempt to maximize fertility and by the use of genetically superior stallions. Associated with artificial insemination, the cryopreservation biotechnique allows the formation of a genetic bank of animals of high breed and commercial standard (Yimer et al, 2016) and the possibility of a stallion obtaining hundreds of descendants throughout its reproductive life (Canisso et al, 2008). Numerous studies are constantly developing and demonstrate advantages in its use, the frozen semen of stallions still presents variable fertility results (Santos et al, 2015). Research indicates that cryopreservation increases the production of reactive oxygen species (ROS) by spermatozoa (Lucio et al, 2016) and decreases antioxidant defenses present in semen (Martínez-Páramo et al, 2012)
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