Horse Breeding Arithmetic: 2 + 2 = 1 (2000)
Wayne Eugene Loch, John Walter Massey · MOspace Institutional Repository (University of Missouri) · 2000
"On the average, two mares taken to the stallion for one service each and returned home for the remainder of the season will give birth to one foal--if you are lucky. The national average foal rate for mates bred is approximately 50 percent."--First page.