Endocrine patterns of the post-partum cow

Area of Science:

• Reproductive endocrinology
• Veterinary science
• Animal reproduction

Background:

• Post-partum anestrus is a significant concern in cattle reproduction.
• Factors influencing the resumption of ovarian cyclicity include milking vs. suckling, seasonality, and suckling intensity.
• Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) play critical roles in the estrous cycle.

Purpose of the Study:

• To investigate the factors affecting the resumption of ovarian cyclicity in post-partum cows.
• To elucidate the roles of FSH and LH in initiating ovarian activity after calving.
• To determine the influence of milking versus suckling and seasonal effects on reproductive hormone profiles.

Main Methods:

• Observational study comparing milked and suckled dairy and beef cows.
• Measurement of plasma hormone levels, including FSH, LH, and prolactin.
• Analysis of seasonal influences and suckling intensity on reproductive parameters.

Main Results:

• Milked cows exhibit a shorter interval to ovarian cyclicity compared to suckled cows.
• Spring-calving cows experience delayed cyclicity, with increased suckling intensity further prolonging anestrus.
• LH release patterns, characterized by increased pulsatility and preovulatory surges, are critical for initiating ovarian cyclicity, appearing earlier in dairy than beef cows and being delayed by suckling.

Conclusions:

• The pattern of LH release is definitive for initiating post-partum ovarian activity in cows.
• Milking facilitates a faster return to cyclicity than suckling, influenced by seasonal factors and suckling management.
• FSH recovery precedes LH recovery, and prolactin levels do not correlate with reproductive failure.