A lot depends on the age and size of the male. IMHO, a young male who has just started producing plugs and over 650 grams should only go to a couple of females his first season with multiple days of rest between each one. More females the next season if he grows well. When the males are over 1000 grams and over 3 years old, 5 or 6 females are easily serviced if you are careful and make ure there are rest periods of longer than 1 day each week.

Now, if you are using an ultra sound and only leave the male for a day with the females who are ready to go, a mature male can service even more females. I'm still saving for that ultrasound.