Relationship between endogenous estradiol-17 beta and estrous behavior in heifers

Area of Science:

• Reproductive endocrinology
• Animal science
• Veterinary medicine

Background:

• Endogenous estradiol-17 beta plays a crucial role in regulating estrous behavior and reproductive cycles in cattle.
• Understanding the influence of hormonal interventions on estrous traits is vital for optimizing breeding programs.

Purpose of the Study:

• To investigate the relationship between endogenous estradiol-17 beta concentrations and estrous traits in Holstein heifers.
• To compare estrous traits and estradiol-17 beta levels during a natural estrous cycle and a gonadotropin-induced superovulation period.

Main Methods:

• Thirty-five Holstein heifers were monitored during a non-superovulation period (NSP) and a subsequent gonadotropin-induced superovulation period (SP).
• Blood samples were collected every 6 hours for 120 hours during both periods to measure estradiol-17 beta and progesterone.
• Estrous behavior was continuously observed for 98 hours during both NSP and SP.

Main Results:

• Peak estradiol-17 beta concentrations were significantly higher during SP (49.0 pg/ml) compared to NSP (12.9 pg/ml).
• Estrus duration was longer during SP (2.3 hours) than during NSP.
• The number of behavioral interactions during estrus did not differ significantly between NSP and SP.

Conclusions:

• While peak estradiol-17 beta levels differ markedly between natural and induced superovulation periods, estrous traits show less variation.
• Hormonal manipulation for superovulation significantly elevates estradiol-17 beta without proportionally altering estrous behavior duration or intensity.