Ovarian function in suckling and non-suckling beef cows post partum

Area of Science:

• Reproductive endocrinology in beef cattle
• Lactational anestrus and postpartum ovarian function

Background:

• Postpartum anestrus is a significant challenge in beef cattle production.
• Lactation intensity, particularly suckling, is known to influence the resumption of ovarian cyclicity.

Purpose of the Study:

• To investigate the impact of suckling on the resumption of ovarian cyclicity in postpartum beef cows.
• To compare hormonal profiles (prolactin, LH) and estrous behavior between suckling and non-suckling cows.

Main Methods:

• Two groups of 7 crossbred beef cows (suckling vs. non-suckling) were fed high-quality diets ad libitum for 3 months postpartum.
• Ovarian cyclicity, plasma glucose, prolactin, and luteinizing hormone (LH) concentrations were monitored.
• Response to estradiol benzoate injection was assessed in some cows.

Main Results:

• Non-suckling cows resumed ovarian cycles within 10-33 days postpartum; suckling cows did not cycle until at least 14 weeks postpartum.
• Plasma prolactin showed a seasonal trend in non-suckling cows, less evident in suckling cows.
• Suckling cows had lower plasma LH before Day 30 and failed to exhibit estrus or LH surge post-estradiol benzoate challenge.

Conclusions:

• Suckling significantly delays the resumption of ovarian cyclicity in beef cows.
• The observed hormonal patterns and lack of estrus response suggest hypothalamic dysfunction in suckling cows, impairing reproductive cyclicity.