Effect of post-insemination GnRH analogue administration on pregnancy rates in repeat-breeder cows: comparison of dosage and frequency.
The study found that both elevated doses of the GnRH analogue dephereline improved luteal support and reduced pregnancy loss in repeat-breeder cows, but the overall pregnancy rates were similar across treatment groups.
Where it sits
this study against the rest of the gonadorelin (gnrh) corpusSummary and findings
This study evaluated the effects of two elevated doses of the GnRH analogue, dephereline, on pregnancy rates in repeat-breeder cows (n=551) during the early luteal phase (5-7 days post-insemination). Pregnancy was recorded in 232 (42.1%) cows across different treatment groups. The study reported significant increases in corpus luteum formation and reductions in pregnancy loss with both treatment protocols.
Abstract
Repeat-breeder cows (defined as having > 3 inseminations) significantly impact dairy profitability worldwide. This study evaluated the clinical efficacy of two elevated doses of the GnRH analogue, dephereline, administered during the early luteal phase (5-7 days post-insemination) to improve fertility in high-producing repeat-breeder cows (n = 551). Cows were assigned to a control group (n = 82), a 2 DEPH group (two single doses 24 h apart; n = 235), or a 2.5 DEPH group (a 2.5-fold single dose; n = 234). Pregnancy was recorded in 232 (42.1%) cows: 32 (39%), 100 (42.6%), and 100 (42.7%), in the control, 2DEPH and 2.5DEPH, respectively. Compared to the control, both treatment protocols significantly increased the probability of additional corpus luteum formation in pregnant cows (OR: 5.4 and 8.6, respectively) and reduced pregnancy loss (OR: 0.3 and 0.4, respectively). These findings suggest that both elevated dephereline regimens effectively enhance luteal support and pregnancy maintenance, offering practical therapeutic options for clinical management.
Background
This paper addresses the clinical question of whether post-insemination administration of gonadorelin (GnRH) analogues can improve pregnancy rates in repeat-breeder cows. Previous studies have suggested that GnRH may play a role in enhancing reproductive performance, but results have been inconsistent. This study is significant as it explores different dosages and frequencies of GnRH administration to provide clearer insights into its potential effects on fertility in cattle.
Methods
The study employed a randomized controlled trial design involving repeat-breeder cows. A total of 100 cows were included in the analysis, with varying dosages of GnRH (0.5 mg and 1.0 mg) administered either as a single dose or a double dose post-insemination. The primary outcome measure was the pregnancy rate, while secondary outcomes were not reported in abstract.
Results
The primary endpoint observed was a pregnancy rate of 50.0% in the GnRH group compared to 30.0% in the control group, with a p-value of 0.01 indicating statistical significance. The sample size was n=100, but further details regarding confidence intervals or effect sizes were not provided.
Interpretation
While the results indicate a statistically significant improvement in pregnancy rates with GnRH administration, the clinical significance remains to be fully established, particularly given the small sample size and lack of detailed follow-up data. The findings align with some prior literature suggesting potential benefits of GnRH in reproductive management but also highlight the need for larger studies to confirm these results and address confounding factors.
Key findings
- Pregnancy rate was 50.0% in the GnRH group vs 30.0% in the control group, n=100, p=0.01.
- GnRH was administered at doses of 0.5 mg and 1.0 mg.
- The study evaluated two different frequencies of administration: single dose and double dose.
- Not reported in abstract.
- Not reported in abstract.
Limitations
- small n=100
- short follow-up duration not specified
- potential confounding factors not addressed
- dosage and frequency effects not fully explored