REFERENCE : Bruinje et al. Relationships among early postpartum luteal activity, parity, and insemination outcomes based on in-line milk progesterone profiles in Canadian Holstein cows. Theriogenology 2017, 100, 32-41.

BACKGROUND

The waiting period is a high-risk period for subsequent fertility in primiparous and pluriparous cows. This involves optimal follicular growth, which in turn depends on resuming optimal luteal activity as early and consistently as possible.

The authors conducted a study on two farms in Canada (calving interval between 389 and 398 days and waiting period of 68 to 71 days, average daily milk production during the first 60 days postpartum of 30 liters for primiparous cows and 44 liters for pluriparous cows in three daily milkings, The results of the study were used to compare the progesterone monitoring of 748 primiparous (350) and pluriparous (398) cows by means of the Herd-navigator (evaluation of progesterone levels every two days between the 21st day postpartum and the 55th day following the last insemination).

THEIR OBSERVATIONS

• 76 and 79% of primiparous and pluriparous animals, respectively, showed luteal activity during the first 50 days postpartum (Figure 1): not bad at all.
• In primiparous cows, the percentage of pregnancy decreased with increasing time from calving to the appearance of luteal activity; the same was true for pluriparous cows. This decrease appears especially after day 28 in primiparous cows and day 56 in pluriparous cows. In pluriparous males, the late onset of luteal activity results in an increased risk of embryonic mortality due to the fact that exposure to progesterone impregnation was shorter (Figure 2).
• The number and duration of progesterone phases contribute to increased pregnancy rates in primiparous and pluriparous animals (Figure 3). Abnormal luteal phase is defined as those lasting less than 7 days or more than 19 days.

CONCLUSIONS

Precocity, number and quality of luteal phases condition fertility. LH is at the crossroads of intake capacity, milk production level (and therefore hepatic catabolism of estrogens and progesterone), and uterine infections. The low percentage of animals not cycled at the end of the 50-day waiting period suggests that there is still room for improvement on most of our dairy farms.

The earlier and more often a normal corpus luteum appears after calving, the better the pregnancy percentage at first insemination and the lower the risk of embryonic mortality.