Ok, googlefoo. I only searched gsd. Smaller, younger dogs can go into heat 3 or 4 times a year. Too young and underdeveloped to produce healthy puppies, and not allowing more than two litters is supposed to discourage this.Dogs generally go into heat twice a year. Pregnancy lasts around 63 days. They are nursing their pups for 4+ weeks. How are dogs having more than two litters a year?
When we had a breeding pair of Maremmas, there would be a litter about every 9 months.