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The concentration of unoccupied luteal receptors for luteinizing hormone (LH) and prolactin, and the concentration of these two hormones in the pituitary was determined in 11 groups of bitches (n = 3 or 4/group) representing stages from proestrus through Day 80 of diestrus. Despite dramatic changes in serum concentrations of progesterone, the concentration of luteal receptors for LH and prolactin was quite constant throughout the entire luteal phase. In association with the ovulatory surge of LH, pituitary concentration of LH decreased abruptly from proestrus to Day 2 of diestrus, and was then gradually replenished during the remainder of diestrus. The concentration of prolactin in the pituitary did not vary significantly from proestrus through late diestrus.

Embryo transfer is a biotechnology that has been used worldwide to increase the production of offspring from female bovines. Treatments to induce multiple ovulations (superovulation) have evolved from superstimulatory protocols that depended upon detection of oestrus to treatments that synchronise follicle growth and ovulation, allowing for improved donor management and fixed-timed AI (FTAI). The protocols associated with FTAI facilitate animal handling and produce at least as many viably embryos as conventional treatment protocols that required detection of oestrus. Recent knowledge regarding LH receptors (LHR) and follicular development can be applied to improve embryo transfer protocols. In fact, improvements in the superstimulatory treatment called the 'P-36 protocol', which include hormones that stimulate LHR, indicate that adjustments related to LHR availability may increase bovine embryo yield compared with conventional protocols based on the detection of oestrus.