Luteolysis was induced in 5 experimental Beagle (8 cycles) and 7 client-owned bitches treated with 150 to 200 mu g/kg, sc of prostaglandin F2 alpha administered twice daily for 4 d, starting on Days 8 to 19 after the onset of cytological diestrus. Five experimental Beagle bitches had been mated during the estrus preceding treatment, and copulation had been confirmed in 2/7 client-owned bitches presented for termination of unwanted pregnancy. Serum
progesterone concentration (mean+/-SD) declined from 26.1 +/- 6.6 ng/ml before treatment to 0.3 +/- 0.4 ng/ml on the fourth day of treatment. One of the 7 client-owned bitches maintained her pregnancy even though serum
progesterone concentrations were less than 0.5 ng/ml on the third and fourth day of treatment. Mean (+/- SEM) interestrous intervals before and following prostaglandin-induced
luteolysis were 207.3 +/- 12.4 (n = 11 cycles in 6 bitches) and 95.5 +/- 20.0 d (n = 6 cycles in the same 6 bitches; P , 0.0001), respectively. These results ...