Coenzyme Q10 and melatonin protect cryopreserved equine sperm against lipoperoxidation

The objective of the experiment was to evaluate the effect of the addition of different concentrations of the antioxidants Coenzyme Q10 (CoQ10) and melatonin to equine semen freezing diluent, alone or in combination, during the cryopreservation process. Twenty ejaculates (n = 5 stallions) were divided in groups: Control (C, without the addition of antioxidants), melatonin 0.75 mM (MEL1), melatonin 1.5 mM (MEL2), CoQ10 40 μg/mL (Q1), CoQ10 200 μg/mL (Q2), and CoQ10 40 μg/mL+ 0.75 mM melatonin (Q1 +MEL1). Q1 and Q2 groups demonstrated intact plasma membrane and high mitochondrial membrane potential after 30 (M-30) and 60 (M-60) min of incubation compared with the control group (Q1: 64.8 % ± 9.9 %, Q2: 65.2 % ± 10.5 %, C: 55.1 % ± 10.0 %; M-30 and Q1: 63.3 % ± 10.4 %, Q2: 64.6 % ± 10.8 %, C: 53.1 ± 10.6 %; M-60; P < 0.05). Melatonin conferred greater membrane stability at all evaluated times compared with the control group (MEL1: 42.1 % ± 6.0 %; MEL2: 44.0 % ± 6.7 %, C: 35.9 % ± 5.9 %; M-0; MEL1: 40.8 % ± 5.6 %; MEL2: 42.6 % ± 7.2 %, C: 33.1 % ± 6.6 %; M-30 and MEL1: 37.5 % ± 7.4 %; MEL2: 39.1 % ± 7.2 %; C: 31.3 % ± 6.5 %; M-60; P < 0.05). The use of antioxidants alone or in combination resulted in lower levels of lipoperoxidation at all times evaluated compared with in the control group (P < 0.05). In conclusion, CoQ10 and melatonin were effective in the cryopreservation of equine semen by decreasing lipoperoxidation and promoting a higher percentage of spermatozoa with a high mitochondrial potential, total and progressive motility, and prevention of membrane lipid disorder.