Use of gonadorelin to optimize ovarian response during superovulation in Holstein cows

Abstract

In highly productive Holstein herds, variability in ovarian response remains a key limiting factor in the effectiveness of embryo transfer programs. It is known that the imported preparation Pluset (FSH:LH ratio of 1:1) reliably induces ovulation, whereas the domestic FSH-Super (FSH:LH ratio of 1000:1) demonstrates lower efficacy, presumably due to LH deficiency. The aim of this study was to quantitatively and qualitatively assess whether the additional administration of gonadorelin (as a source of the LH/FSH surge) can compensate for the low LH content in a standard superovulation protocol using FSH-Super in Holstein cows.
The study included 38 Holstein cows in their 2nd–3rd lactation (TPI ≥ 2590), divided into a control group (n = 17) and an experimental group (n = 21). Both groups received an 18-day protocol involving a CIDR device, four injections of FSH-Super (total dose: 1000 IU), and prostaglandin. In the experimental group, 100 µg of gonadorelin was additionally administered on day 9. Ovarian response was evaluated by the number of corpora lutea; embryo productivity was assessed based on total embryo yield, mean embryos per cow, and embryo quality.
In the experimental group, the number of corpora lutea ranged from 5 to 12 (most commonly 8–10), while in the control group the range was 3 to 8 (commonly 4–6). A total of 134 embryos were obtained in the experimental  group versus 81 in the control (a 65.4% increase); the average yield per cow was 6.4 ± 0.5 and 4.8 ± 0.4, respectively (p = 0.012). The proportion of embryos suitable for transfer did not differ significantly between groups.
Thus, the inclusion of gonadorelin in the FSH-Super protocol significantly increases quantitative indicators of superovulation without compromising embryo quality, supporting the feasibility of implementing the modified protocol in reproductive biotechnology for high-yielding dairy herds.