When is the best time/period for spaying a bitch?

The best time is the 'rest period' - of sexual inactivity- between the 'half-yearly' heat or oestrus periods. A bitch normally has 2 periods of 3 weeks per year during which the ovaries are active. The an-oestrus period in-between is the perfect time for spaying. The best age for spaying is 3-4 months after the first heat or oestrus. Other possibilities can be discussed.