Figure 3. Potential mechanism by which fish meal may improve fertility of lactating dairy cows. If conception does not occur (left side), the uterus secretes PGF2-alpha at the end of the estrous cycle to regress the corpus luteum (CL) and recruit a new follicle for another ovulation. If conception does occur (right side), PGF2-alpha is not released from the uterus and the CL is maintained on the ovary to produce progesterone to preserve the life of the embryo. Unique fatty acids in fish meal may help suppress synthesis of PGF2-alpha.