Clinical use of prostaglandin F2 alpha to induce early abortion in bitches: serum progesterone, treatment outcome and interval to subsequent oestrus

Records of elective abortion in 27 bitches presented to the Veterinary Surgery and Reproduction Clinic of the University of Pisa were reviewed. Treatment consisted of twice-daily subcutaneous injections of 150-270 micrograms natural prostaglandin F2 alpha kg-1 for 4 consecutive days starting between cytological dioestrous days 5 and 19. None of the treated bitches whelped. Luteolysis appeared to be complete (serum progesterone < 3.2 nmol l-1) at the end of treatment in 22 of 25 bitches in which progesterone was assayed in serum obtained daily during therapy. Serum progesterone rose after treatment to a concentration consistent with pregnancy in four of 17 bitches in which progesterone was measured once between dioestrous days 23 and 51. The mean intercycle interval (pro-oestrus-pro-oestrus) of the cycle in which abortion was induced was 134 +/- 45 days for 15 dogs for which the interval could be determined, and was significantly shorter than the average preceding interoestrous intervals (210 +/- 40.0 days) for the same dogs (P < 0.001).