Intravaginal progesterone insert used in the beef cattle, dairy cattle, goat and sheep industries. CIDRs have also been used in gazelles bred in captivity.  The progesterone is released at a controlled rate into the bloodstream after insertion. In all species, CIDRs are used for the synchronization of estrus. This can be highly beneficial in large herds because with the synchronization of estrus, groups of cows and heifers can be bred at the same time in a narrow window.   In beef cattle specifically, CIDRs advance the first estrus in anestrus postpartum beef cows and in pre-pubital beef heifers.