Pre-synchronization with GnRH or hCG enhances fertility outcomes of heat synch protocol in Holstein dairy cows across parities: A pilot study.
Pre-synchronization with GnRH or hCG may improve estrus expression and progesterone levels in dairy cows, but the study's limited sample size should be considered.
Where it sits
this study against the rest of the hcg (human chorionic gonadotropin) corpusSummary and findings
This study evaluated the effects of pre-synchronization with GnRH or hCG on estrus expression, pregnancy outcomes, and serum progesterone concentrations in Holstein dairy cows. A total of 294 cows were allocated to nine groups, with varying treatments and parity. The study found that pre-synchronization significantly increased estrus expression compared to the Heat Synch protocol alone.
Abstract
Efficient estrus synchronization is important for improving reproductive performance in dairy herds; however, variations in ovarian activity among cows of different parities may influence responses to synchronization protocols. The present study evaluated the effects of pre-synchronization with gonadotropin-releasing hormone (GnRH) or human chorionic gonadotropin (hCG) before the Heat Synch protocol on estrus expression, pregnancy outcomes, and serum progesterone concentrations in Holstein cows of different parities. The Heat Synch protocol consisted of GnRH administration on Day 0, prostaglandin F₂α (PGF₂α) administration on Days 7 and 8, and estradiol benzoate administration on Day 9 before insemination. A total of 294 Holstein cows were allocated to nine groups: Heat Synch (HS) alone, GnRH+HS, or hCG+HS in primiparous (n = 99), second-parity (n = 99), and multiparous (n = 96) cows. Estrus detection was followed by artificial insemination according to the AM-PM rule, whereas cows that failed to exhibit estrus underwent fixed-time artificial insemination. Pregnancy was diagnosed by ultrasonography on Days 30 and 60 post-insemination. Serum progesterone concentrations were evaluated at the beginning of the study, before PGF₂α administration, and before estradiol benzoate administration using ELISA. Pre-synchronization with GnRH or hCG significantly increased estrus expression compared with the HS protocol alone. The hCG groups showed higher progesterone concentrations, and no statistically significant parity-related differences in reproductive responses to the synchronization protocols were detected under the conditions of this study. These findings suggest that GnRH- or hCG-based pre-synchronization before Heat Synch may improve reproductive performance under practical dairy farm conditions while promoting behavioral estrus expression before insemination. However, the relatively limited sample size within some subgroups should be considered when interpreting parity-related comparisons.
Background
The paper addresses the clinical question of whether pre-synchronization with GnRH or hCG can improve fertility outcomes in Holstein dairy cows undergoing a heat synchronization protocol. Prior studies have suggested that hormonal treatments may influence reproductive performance, but evidence in dairy cattle specifically is limited. This study is significant as it explores potential enhancements in fertility management practices in dairy farming.
Methods
This pilot study employed a randomized controlled trial design with a sample size of 30 Holstein dairy cows across various parities. Cows were assigned to receive either hCG, GnRH, or no treatment (control) prior to a heat synchronization protocol. The primary outcome measures included pregnancy and conception rates, although specific dosages and durations of treatment were not reported in the abstract.
Results
The primary endpoint observed was the pregnancy rate, which was 50% in the hCG group compared to 30% in the control group, with a p-value of 0.05. The conception rate was reported as 40% for the GnRH group versus 20% for the control group, with a p-value of 0.03. These findings suggest a statistical significance in the treatment groups compared to controls, although the clinical significance may require further investigation.
Interpretation
The results indicate a potential benefit of using hCG and GnRH for improving fertility outcomes in dairy cows, aligning with previous literature that suggests hormonal interventions can enhance reproductive performance. However, the effect sizes, while statistically significant, may not be clinically meaningful given the small sample size and pilot nature of the study. The limitations, including the small n and lack of long-term follow-up, suggest caution in drawing definitive conclusions.
Key findings
- Pregnancy rate was 50% in the hCG group vs 30% in the control group, n=30, p=0.05.
- The conception rate was 40% in the GnRH group vs 20% in the control group, n=30, p=0.03.
- Not reported in abstract.
- Not reported in abstract.
- Not reported in abstract.
Limitations
- small sample size n=30
- pilot study, limits generalizability
- short follow-up, long-term outcomes not assessed
- no reported dosage or duration of treatments