نبذة مختصرة : Annual fluctuations of DNA fragmentation and characteristics of raw and cold-stored sperm were evaluated weekly during one year in 15 stallions. In fresh semen ejaculate volume, sperm concentration, total sperm count and sperm motility were determined. In cold-stored semen (24, 48 h), sperm motility, the percentages of sperm with intact plasma membrane and acrosome and of viable sperm with low intracellular Ca2+ level were determined. SCSATM was performed to assess DNA fragmentation of sperm (mean DFI, SD of DFI, % DFI) in raw frozen-thawed as well as in cold-stored sperm. The month of semen collection affected (P<0.05) all parameters evaluated in raw semen and all criteria except progressive motility and rapid cells after 24 and 48 h of storage, respectively. Seasonal changes in DNA fragmentation were most evident with respect to mean DFI. In raw semen mean DFI was lower from August to November than in June and July (P<0.001). Values were lower in winter compared to spring and early summer (P<0.05). After 24 h of cold storage mean DFI was lower in September and October than in January, February, May, July and November (P<0.05). After 48 h of storage mean DFI was reduced in spring and autumn compared to February, June and July (P<0.05). In conclusion, a seasonal effect was evident on raw and cold-stored sperm. Semen quality was impaired in midsummer when low sperm motility and viability were combined with an elevated DNA fragmentation and Ca2+ level of sperm.
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