Increased sperm output of rabbits and bulls treated with prostaglandin F2α

Seven rabbits were ejaculated four times once weekly, and saline or 2.5 mg PGF_2α tromethamine salt was injected sc at 4 and 2 hours or at 8 and 4 hours before ejaculation. First ejacula taken at 2 hours after the second injection of PGF_2α contained 150% more (P.07) sperm than those after injections of saline. The comparable difference (60%) at 4 hours after PGF_2α was not significant. PGF_2α did not influence sperm output in second, third or fourth ejacula. After 28 daily sc injections of 5 mg PGF_2α in another experiment, the fertility of four treated rabbits was as high as that for four controls. Without sexual preparation in seven bulls, im injections of 40 or 80 mg PGF_2α 30 minutes before ejaculation resulted in 33% greater (P<.05) sperm output than that after injection of 0, 7 or 20 mg PGF_2α, but the highest sperm output after PGF_2α was 30% less (P<.05) than that after sexual preparation in the same bulls. We conclude that injections of PGF_2α result in increased sperm output in ejacula taken without sexual preparation within 2 hours in rabbits and in bulls.