Estrus, Ovulation, And Serum Progesterone, Estradiol, And LH Concentrations In Mares After An Increased Photoperiod During Winter

The study involved 15 seasonally anestrous mares divided into three groups to assess the effects of increased photoperiod on estrus, ovulation, and hormone concentrations. The indoor light-treated group, exposed to a 16-hour photoperiod, ovulated significantly earlier than the control groups, with ovulation occurring 59 days after treatment began, which was 74 days earlier than the outdoor controls and 50 days earlier than the indoor controls. The light-treated mares also experienced more estrous cycles before April 21 and showed earlier hair loss. Hormone levels associated with the estrous cycle were observed to normalize with the onset of estrus. The study concluded that increasing the photoperiod in early December could induce normal estrous cycles in anestrous mares within two months, potentially allowing for earlier breeding and foaling.