Endocrine aspects of uterine involution in the cow

The postpartum period (PP) (=puerperium) is characterized by involution of the uterus and recyclicity of the ovarian functions to prepare the animal f or a new pregnancy period. The time required for the genital organs to beco me normalised is influenced by breed, management including feeding regimens and environmental factors. This period is also strongly influenced by peri parturient diseases such as dystocia, paresis (puerperalis), mastitis, endo metritis, etc. The period is also influenced by several hormonal changes. D uring the postpartum period in the cow, a massive release of PGF(2 alpha) o ccurs concomitantly with the uterine involution. In cows with retained foet al membranes (RFM), a second pulsatile release of PGF(2 alpha) is seen conc omitant with the growth and final elimination of bacteria. A similar patter n is seen in cows with induced parturitions with e.g. dexamethasone, indica ting the occurrence of RFM/endometritis as a consequence of the induction. The duration of these prostaglandin releases are negatively correlated to u terine involution in normal cows and positively correlated in cows with RFM /endometritis respectively. As long as the release is maintained, the cow i s unable to ovulate and it therefore seems likely that PGF(2 alpha) or othe r products in the arachidonic acid cascade can inhibit the ovarian activity . Onset of ovarian cyclicity influences to a high degree the uterine involu tion, however most common is that the first ovarian cycle is shorter than s een during the normal oestrous cycle. The uterine involution process can be enhanced by treatments with exogenous PGF(2 alpha). No effect on uterine i nvolution in healthy cows, or a slight positive effect, is seen after treat ment with prostaglandin synthesis inhibitors (e.g. flunixin meglumine). The aim of this presentation is to review some of the knowledge of the interac tions between the uterus and ovaries during the postpartum period in cattle .