Altered progesterone concentrations by hormonal manipulations before a fixed-time artificial insemination CO-Synch +
S L Hill1, G A Perry2, V R G Mercadante3
1Department of Animal Sciences and Industry, Kansas State University, Manhattan, Kansas, USA.
Theriogenology
|April 22, 2014
Summary
Altering progesterone status before timed artificial insemination (TAI) in beef cows enhanced luteolysis and ovulation but did not improve pregnancy per TAI. Elevated progesterone before TAI benefited anestrous cows, while cycling cows were unaffected.
Area of Science:
- Reproductive biology
- Veterinary science
- Animal science
Background:
- Optimizing timed artificial insemination (TAI) protocols in suckled beef cows is crucial for reproductive efficiency.
- Progesterone status before TAI influences fertility, but optimal pre-synchronization strategies require further investigation.
- Previous research suggests manipulating the estrous cycle can impact TAI success rates.
Purpose of the Study:
- To test the hypothesis that inducing luteal regression or ovulation before TAI improves pregnancy outcomes in beef cows.
- To evaluate the effect of pre-synchronization treatments (PGF2α or PGF2α + GnRH) on progesterone profiles and TAI success.
- To determine if altering progesterone status pre-TAI impacts fertility in different physiological states (e.g., anestrous vs. cycling).
Main Methods:
- Two experiments were conducted using suckled beef cows subjected to a CO-Synch + controlled internal drug release (CIDR) TAI program.
- Experiment 1: Cows received PGF2α (PrePG) 13 days before GnRH-1 (Day -13 vs. control).
- Experiment 2: Cows received PGF2α and GnRH (PrePGG) 20 and 17 days before GnRH-1 (Day -20/-17 vs. control). Blood samples were collected for progesterone analysis.
Main Results:
- Pre-synchronization treatments enhanced luteolysis and increased the proportion of cows ovulating after GnRH-1 in Experiment 1.
- Pregnancy per TAI was not significantly improved in either experiment with pre-synchronization treatments.
- In combined data, anestrous cows with elevated progesterone pre-TAI had improved pregnancy outcomes, unlike cycling cows.
Conclusions:
- Pre-synchronization treatments effectively altered progesterone status and enhanced ovulation responses before TAI in beef cows.
- Despite enhanced ovulation, these specific pre-synchronization protocols did not improve overall pregnancy per TAI.
- Progesterone concentration pre-TAI is a significant factor for pregnancy success in anestrous cows but not in cycling cows.
