Change in Morphology of Spermatozoa from Dismount Semen during the Breeding Season in Thoroughbred Stallions in Japan.
To clarify the physiological changes of sperm morphology in active Thoroughbred stallions during the breeding season, we examined the dismount semen collected from the penile urethra immediately after service. The spermatozoa were analyzed for relationships between the morphology and the stallion's age or the number of services. Seasonal variation was apparent in the rate of the sperm tail abnormalities, spermatozoa with cytoplasmic droplets, appearance of medusa cells, and sperm head length. Area and width of the sperm head correlated negatively with age (P<0.05). The rate of appearance of medusa cells and the length of the sperm head were positively related to the number of services (P<0.05), and the aspect ratio was negatively related (P<0.01).
Department of Large Animal Clinical Sciences, Graduate School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan.
Masanori
M
Koyago
Department of Large Animal Clinical Sciences, Graduate School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan.
Ken
K
Nakada
Shadai Corporation, Abira, Hokkaido 059-1500, Japan.
Nobuo
N
Tsunoda
Department of Large Animal Clinical Sciences, Graduate School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan.
Masaharu
M
Moriyoshi
Department of Large Animal Clinical Sciences, Graduate School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan.
Yutaka
Y
Sawamukai
Thoroughbred stallion; breeding season; spermatozoa morphology