Semen quality evaluation in young stallions - feasibility and comparison of two different protocols

Semen analysis is a valuable approach to assess male fertility in the horse. The aim of this study was to evaluate the effects of two different semen collection protocols, stallion's age, season and previous rearing conditions on sperm parameters of young stallions. Semen samples were obtained from 23 stallions (age range: 30-42 months old) every six weeks. Stallions were reared under different conditions prior to the start of the study. Semen collection was either performed twice with an interval of one hour on a given day (protocol A) or once daily for seven days (protocol B). The ejaculates were examined for total sperm number (TSN), progressive motility (PM), plasma membrane integrity (PMI), DNA fragmentation index (DFI) and semen quality after storage at 5 degrees C for 24 hours. TSN and DFI were higher for protocol A as compared to protocol B. TSN in stallions submitted to protocol A (1st ejaculate) was influenced by season, whereas TSN remained unchanged in stallions submitted to protocol B. PM exceeded 70% in every ejaculate and the protocol did not significantly affect motility. PMI was lower in ejaculates of 33.4 months old stallions on average as compared to older individuals. No other semen parameter was affected by the stallions' age. In conclusion, breeding soundness examination in 33.4 months old stallions is feasible and semen analysis after daily collection for 7 days provides less variable results throughout the year than semen analysis with protocol A. Therefore, semen analysis after daily collection for 7 days is recommended for young stallions.