For example, mares that may not have previous records do not give you a clue as to follicle size before ovulation, deviation of heat, etc. Whereas mares which you do have a history of estrus length and normal follicle size before ovulation can be bred fewer times without the fear of missing ovulation. Overall foaling rate is the best indicator of success of the breeding season but embryo and fetal loss rates are needed to identify important differences at specific times of gestation. The embryo loss rates can be calculated for mares that lose a pregnancy between 14 - 20 days after initially determined to be pregnant. The fetal loss rate would be during the 20 to 40 day period.
Most farms now breed on foal heat.
The mathematical information obtained will provide information for making decisions on mare management, allow evaluation of operational success in producing foals, and provide evidence of the need for changes in breeding management activities.