Since 1973 exogenous progestins have been used in
equine practice for pregnancy maintenance, estrus suppression,
estrus synchronization, control of erratic sexual
behaviour, and hastening of the first ovulation in transitional
mares. This study was designed to investigate the
use of a newly compounded controlled-release progesterone
preparation (BioRelease P4 LA 300TM, BET PHARM
LLC, Lexington, KY) in early and late spring transitional
mares.