Stability over Time of the Sperm Motility Biomarker proAKAP4 in Repeated Dog Ejaculates

ProAKAP4 is a sperm structural protein involved in motility, capacitation, and fertility. Previous studies suggested it as a suitable marker for canine sperm evaluation. Our study aimed to assess proAKAP4 concentration variations among different ejaculates collected from the same dogs. Fourteen male dogs from 12 different breeds, 1-14 years old and 6.9-95 kg bodyweight, underwent semen collection at least twice (1-4 times) during the same or different days. Sperm concentration, morphology, proAKAP4 concentration, total (TM%), and progressive motility (PM%) were considered. ProAKAP4 values were divided into four classes: ≤15, 15-40, 40-60, and >60 ng/10 M spermatozoa. The time interval between two semen collections was classified as: first collection (T0), semen collection performed 2-3 h after the first one (T0.5) and after ≥1 day (1-36 days, T1). Thirty-three ejaculates were collected. A correlation was found between proAKAP4 classes and TM% (r = 0.40, <i>p</i> = 0.049), whereas no correlation was found neither between proAKAP4 and sperm morphology nor for proAKAP4 classes between collection times (T0 vs. T0.5, <i>p</i> = 0.655; T0 vs. T1, <i>p</i> = 0.564). Our results confirm the correlation between proAKAP4 and TM% in dog semen. ProAKAP4 concentration appears stable in different ejaculates collected from the same dogs. Further studies are needed on the relationship between proAKAP4 and other canine semen parameters and fertility outcomes.