The post-thaw quality, antioxidant activity, and in vivo fertility of Zaraibi buck semen frozen-stored in the presence of different concentrations of either quercetin or L-arginine.

Over the last decade, there has been a growing interest in incorporating specific additives into buck semen extenders to enhance their semen quality, as their antioxidant defense against oxidative stress and lipid peroxidation is insufficient. Due to their strong antioxidant capabilities, quercetin (QUE) and L-arginine (LA) have garnered considerable interest among these additives. Therefore, this study investigates the effect of adding various concentrations of either QUE or LA in the cryopreservation extender on the post-thaw sperm characteristics, kinematics, enzymatic antioxidant activity, and in vivo fertility of buck semen. Ejaculates were collected from 9 healthy Zaraibi bucks using an electroejaculator once a week. Good-quality ejaculates were pooled and dispensed into 7 aliquots; each aliquot was diluted with Tris-egg yolk citrate extender containing: 1) 10 μM QUE; 2) 15 μM QUE; 3) 30 μM QUE; 4) 50 μM QUE; 5) 2 mM LA; 6) 4 mM LA; and 7) the last aliquot was not supplemented with any additive and set as a control (CTRL). Diluted semen samples were equilibrated at 4 °C for 4 h, loaded into French mini straws, sealed, and frozen-stored in liquid nitrogen. Frozen straws were thawed and examined for sperm characteristics and kinematics; also, enzymatic antioxidants, including catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPX), and total antioxidant capacity (TAC), as well as the lipid peroxidation marker malondialdehyde (MDA), were determined. A total of 210 (30 female/group) mature and healthy doe-goats were selected, exposed to estrus synchronization, and inseminated by the prepared frozen-thawed straws to calculate their in vivo fertility rates. The obtained findings revealed that the 30 μM QUE, 50 μM QUE, and 4 mM LA groups had the highest proportions (P < 0.05) of all post-thaw sperm characteristics. Only the 30 μM QUE group had the greatest (P < 0.05) values of all sperm kinematics. Frozen-thawed buck semen's enzymatic antioxidant activity was markedly enhanced by adding either 30 μM QUE or 4 mM LA into the semen extender. The in vivo fertility rates of frozen-thawed straws enriched with either 30 μM QUE (73.33 %) or 4 mM LA (70.00 %) were higher than those of other treatments and the control group (43.33 %). In conclusion, adding either 30 μM QUE or 4 mM LA to the buck semen cryopreservation extender is recommended to improve its post-thaw sperm quality, antioxidant activity, and in vivo fertility.