Corpus luteum growth and function in lactating Holstein cows during spring and summer

Area of Science:

• Reproductive Physiology
• Animal Science
• Environmental Biology

Background:

• Seasonal variations in temperature can affect bovine reproductive cycles.
• Heat stress is a known factor influencing dairy cow health and productivity.
• Understanding corpus luteum function is critical for successful artificial insemination in cattle.

Purpose of the Study:

• To investigate the effects of seasonal temperature differences on corpus luteum development and function in lactating Holstein cows.
• To correlate environmental temperatures with peripheral serum progesterone levels throughout the estrous cycle.
• To assess the potential impact of summer heat stress on bovine fertility.

Main Methods:

• Daily ultrasonography was used to monitor corpus luteum growth and structure.
• Peripheral serum progesterone concentrations were measured throughout the estrous cycle.
• Rectal temperatures of cows were recorded during spring and summer estrous cycles.

Main Results:

• Cows experienced higher rectal temperatures during summer compared to spring, particularly during corpus luteum formation and the luteal phase.
• Despite similar luteal phase length and corpus luteum size, summer progesterone secretion (days 6–18) and peak progesterone levels were lower.
• Central luteal cavities were observed in both seasonal groups.

Conclusions:

• Elevated summer temperatures suppress corpus luteum function in lactating Holstein cows.
• Reduced progesterone secretion during the luteal phase in summer may contribute to decreased fertility.
• Seasonal heat stress negatively impacts reproductive efficiency in dairy cattle.