Maternal behavior and neuroendocrine regulation of suckling-mediated anovulation in cows.

Although it is clear that the initial endocrine deficit contributing to the length of the postpartum anovulatory period in suckled cows is of pituitary origin, this limitation is only operative for about the first 2 weeks of the puerperium. Thereafter, the pattern of LH secretion required for the final stages of follicular development and ovulation is blocked or attenuated through a more centrally regulated phenomenon. Hence, much of the recently published work in this area has focused on regulatory processes within the hypothalamus. This focus ignores the critical issue of exteroceptive signalling. Recent observations in this laboratory suggest that exteroceptive cues responsible for suckling-mediated anovulation are specifically attributable to the dams' own calf, but are not teat-specific. In fact, suckling does not produce an extended anovulatory state in the absence of a maternal-offspring bond. This review provides an historical perspective of investigations leading to this conclusion, and proposes a conceptual working model that links the special senses, maternal behavior and neuroendocrine centers that drive gonadotropin secretion during the puerperium.