Abstract
Egypt is anticipated to be potentially influenced by the global climate warming. Therefore, the current study aimed to evaluate the influence of age on the fertility potential of Arabian stallions during summer breeding months. Arabian horses grouped according to their age into three groups, each involved six stallions: young (5-6 years), middle (11-12 years) and old (15-20 years) age groups, were weekly sampled during the months of July-August. Ejaculates were collected using artificial vagina, Missouri model, and examined for pH, volume, concentration, motility, livability and morphological abnormalities. Serum samples were harvested and assessed for testosterone, total antioxidant capacity (TAC), lipid profile, and copper and zinc levels. Semen pH (P<0.005), spermatozoa motility (P=0.08), sperm morphology (P<0.001), tail abnormalities (P<0.001), and sperm count per ejaculate differed noticeably between stallions' groups. Testosterone (P=0.07) and TAC (P<0.05) concentrations were markedly affected by stallions' age. Cholesterol correlated negatively with sperm normality, but serum copper and zinc levels correlated positively with semen volume, sperm cell count and spermatozoa livability. These results revealed that the fertility of stallions is age-dependent and is prominently influenced by lipid metabolism and oxidative stress during hot summer breeding season. It is highly advisable to provide animals' house (along with feed and drinking water) with the evaporative cooling system and allow morning or late afternoon outdoor activity to bypass the summer hot climates and sustain stallions' fertility.