39 General motility and mitochondrial cytochemical activity of post-thawed semen of pasture-fed Nelore bulls supplemented with palm and soybean oils

Abstract

This study aimed to evaluate general motility and mitochondrial cytochemical activity of post-thawed semen of pasture-fed Nelore bulls supplemented with palm and soybean oils (protected by calcium salts). Twenty-four young male Nellore bulls were randomly assigned to 2 groups: control (CO; corn supplement and distillery grains without the addition of protected fat) and palm and soybean oils association (OP + OS; control supplement + 145 g of protected soybean oil + 145 g of protected palm). The experiment lasted 84 days, and semen was collected for cryopreservation. Post-thawed general sperm motility was assessed by computer-assisted sperm analysis using a computerized analyser (HTR Ivos II; Hamilton Thorne, Beverly, MA, USA). Motility (%), progressive motility (%), velocity average path (μm s⁻¹), linearity (%), and lateral displacement of sperm head (μm) were analysed. Additionally, mitochondrial cytochemical activity was evaluated by co-incubation with 3,3′-diaminobenzidine (DAB; 1 mg mL⁻¹ of PBS) at 37°C (water bath) for 1 h under reduced lighting conditions. Sperm cells were classified based on the mitochondrial activity of their midpiece in a 4-class scale: class 1 (DAB 1; all mitochondria are active; sperm cells with midpiece completely stained), class 2 (DAB 2; sperm cells with active and inactive segments but with prevalence of active stained segments, indicating average to high mitochondrial activity), class 3 (DAB 3; spermatozoa with less than half of the mitochondrial sheath active), and class 4 (DAB 4; spermatozoa totally inactive, with midpiece completely discolored). Data were analysed using SAS statistical program (SAS 9.3, SAS Institute Inc., Cary, NC, USA), and Tukey’s test was used to identify treatments. Study design was completely randomized, and effects were declared significant at P < 0.05. Increased percentage of sperm motility (CO: 30.27 ± 5.44 v. OP + OS: 38.90 ± 4.68) and progressive motility (CO: 17.27 ± 3.84 v. OP + OS: 22.90 ± 3.88) were noticed in post-thawed samples after supplementation. Nevertheless, the addition of palm and soybean oils to the feed promoted a decrease in the percentage of DAB 3 sperm cells (CO: 4.77 ± 1.03 v. OP + OS: 2.06 ± 0.51; P = 0.0267). Therefore, supplementation with palm and soybean oils improves sperm kinetics in post-thawed semen of grazing Nellore bulls.