Nanoemulsions of Sicilian lemon and wild orange essential oils, using soy lecithin as a surfactant, preserve the acrosome of ram sperm post-thawing.

The objective of this study was to evaluate the effect of adding Sicilian lemon and wild orange essential oil nanoemulsion, using soy lecithin as a surfactant, to ram semen freezing extender. The nanoemulsions were prepared by high-energy emulsification method using soy lecithin (5%) as a surfactant. The organoleptic and physicochemical characteristics were evaluated. Semen samples (n = 7) obtained from adult rams (n = 6) were frozen in a Tris-egg yolk extender supplemented with Sicilian lemon or wild orange nanoemulsion at different concentrations (0.0%, 1.5%, 2.5%, and 3.5%). After thawing (37oC, 30 s), the samples were evaluated for kinematics, plasma and acrosomal membrane integrity, and mitochondrial membrane potential. Visually, the nanoemulsions of Sicilian lemon or wild orange essential oil appeared homogeneous, fluid, opaque, without lumps, odorless, and colored, immediately after preparation (0 h) and after thermal stress (24 h). The physicochemical characterization of the nanoemulsions showed vesicles with average sizes < 220.00 nm, polydispersity index < 0.30, and zeta potential of -59.00 mV. Semen samples from the groups treated with Sicilian lemon (1.5%, 2.5%, and 3.5%) or wild orange (1.5%, 2.5%, and 3.5%) nanoemulsions did not differ (P ≤ 0.05) in terms of kinematics, plasma membrane integrity, and mitochondrial membrane potential when compared to the control group. However, the groups treated with Sicilian lemon (2.5% and 3.5%) and wild orange (1.5%, 2.5%, and 3.5%) nanoemulsions had a higher percentage (P ≤ 0.05) of cells with intact acrosomes when compared to the control group. It can be concluded that nanoemulsions of essential oils of Sicilian lemon (2.5% and 3.5%) and wild orange (1.5%, 2.5%, and 3.5%), using soy lecithin (5%) as a surfactant, can be used as additives to the Tris-egg yolk extender for ram semen freezing due to their ability to preserve the acrosome post-thawing.