Effects of Cooling Periods on Equine Semen Characteristics in Al-Zawraa Park
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Chilling stallion semen in equine reproduction prolongs sperm
viability and makes artificial insemination easier, cooling causes
physiological changes that can impact membrane integrity, acrosome
stability, and overall semen quality; monitoring these parameters over time
is crucial to comprehending the limits of semen usability during storage. This
research aimed to evaluate the time-dependent changes in semen quality of
stallions during chilled storage using a Tris-hydroxymethyl-aminomethan
based extender at Al-Zawraa Park, Baghdad. Twelve semen samples were
collected from two stallions from October 2024 to April 2025. Ejaculates were
collected, diluted, and stored at 5 °C for five consecutive days. Daily
assessments included sperm viability, morphological abnormalities, plasma
membrane integrity (HOST), and acrosomal status; the results demonstrated
a progressive decline in semen quality over time. On day 1, semen samples
showed high viability with minimal abnormalities, while plasma membrane
and acrosomal structures were well preserved. From day 2 to day 3, a marked
reduction in membrane integrity was observed accompanied by increasing
morphological defects. By day 5, viability had dropped markedly, membrane
integrity was severely impaired, and acrosomal status revealed limited
fertilization potential. These findings confirm that cold storage, even with
the protective effect of Tris extender, leads to cumulative structural and
functional damage in spermatozoa. Stallion semen preserved at 5 °C with
Tris-hydroxymethyl-aminomethan extender maintains acceptable quality
only for a limited period, with substantial decline beyond 48–72 hours. This
research highlights the importance of functional assays such as HOST and
acrosomal evaluation for predicting fertility potential and suggests that
extender modification or antioxidant supplementation may be required to
prolong semen usability.
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