Abstract
An observation was made on the duration of estrus in 50 mongrel bitches, 24 years of age, weighing about 10 kg each. Twenty three of 31 bitches mated in estrus became pregnant but 8 of them were infertile. Ten bitches were mated with vasectomized dog. The remaining 9 bitches were not subjected to mating.
The duration of proestrus was regarded as an interval between the day of vulval bleeding and the day of onset of acceptance of the male, and the duration of estrus was regarded as that of acceptance of the male.
The copulation tests of bitches were carried out with 4 male dogs, two of them had been vasectomized, after vulval bleeding in the morning and evening everyday.
The copulation test was judged to positive when the bitch showed estrous behavior and allowed the mounting of the male or did not reject the introduction of a finger into vagina.
The day of onset or termination of estrus was determined according to the acceptance of the male either in the morning or evening tests.
Results obtained:(1) The duration of proestrus ranged from 3 to 27 days, 8.3± 2.9 days (mean ± S. D.);(2) The duration of estrus ranged from 5 to 20 days, being 10.9± 3.4 days; (3) The duration of proestrus plus estrus ranged from 11 to 35 days, being 19.4± 2.7 days; (4) The duration of vulval bleeding ranged from 4 to 37 days, being 20.5± 5.0 days.
