Days 0 to 21

•  Non-pregnant gilts and sows normally have a 21-day estrous cycle, with estrus (heat) usually lasting 24 to 72 hours.  The first day that heat is observed is usually designated as day 0.

•  Ovulation normally occurs toward the end of estrus, at which time the follicles release their ova (eggs).  The cells that remain form the copora lutea, the endocrine gland that secretes progesterone.

•  Natural progesterone concentrations increase about 24 hours after ovulation and plateau between days 6 and 10.

•  If developing embryos are not present in the uterus at days 12 to 14, progesterone levels begin to decrease rapidly.

•  By day 16, progesterone levels can be nearly undetectable.  A surge in secretion of FSH (follicle-stimulating hormone) and LH (luteinizing hormone), in turn, stimulates the growth of new follicles, which ultimately results in estrus and ovulation.

Controlling Estrus with MATRIX

MATRIX (altrenogest) delivers several important benefits that go right to your bottom line.

•  Feeding MATRIX for 14 days will effectively synchronize estrus in a selected group of gilts.

•  Administered early in the estrous cycle, on day 1 or 2, MATRIX coincides with the normal internal pattern of progesterone secretion.

•  When administered in the middle of the cycle, e.g. beginning on days 10 to 12, MATRIX treatment is initiated just before naturally occurring progesterone begins to decrease.

•  When administered late in the cycle when progesterone concentrations are low, MATRIX prevents follicular development and heat until it is withdrawn 14 days later.