# Economics of Using GnRH on Day 5 After Timed Artificial Insemination in a Modified Double-Ovsynch Protocol at a Low-Fertility Dairy Farm

## TL;DR

This study shows that adding a GnRH agonist to a fertility protocol improves pregnancy rates and profitability in low-fertility dairy cows.

## Contribution

A modified Double-Ovsynch protocol with GnRH on day 5 post-TAI increases pregnancy rates and economic returns in anoestrus dairy cows.

## Key findings

- Pregnancy rates were 35.1% in the GnRH-treated group versus 26.5% in the control group.
- The modified protocol increased net present value by USD 54.2 per anoestrus cow per year.
- The treatment significantly affected accessory corpus luteum occurrence (p < 0.0001).

## Abstract

In the dairy cattle industry, the establishment and maintenance of pregnancy are critical factors influencing herd profitability. Researchers have concentrated their efforts on developing strategies aimed at enhancing fertilization rates and mitigating the adverse effects associated with poor embryo survival, which can ultimately lead to embryo resorption. Studies estimate that very early, early, and late embryonic losses in dairy cows can range from 40% to 60%, underscoring the severity of this issue. Embryo losses in anoestrus dairy cows represent a major challenge for reproductive success in the dairy industry. The inability of anoestrus cows to exhibit normal reproductive behaviors can severely limit conception rates and overall productivity within a herd. In light of this challenge, our study examines the effectiveness of a modified Double-Ovsynch (DO) protocol. This innovative approach incorporates the supplementary administration of a single dose of the GnRH agonist dephereline on day 5 post-timed artificial insemination (post-TAI) to induce corpus luteum (CL) formation and increase the progesterone level. The goal of this adjustment is to improve profitability by decreasing embryo losses, specifically in anoestrus dairy cows.

This study evaluates the effectiveness and financial impact of treating anoestrus dairy cows using a modified DO protocol. Among the 350 cows included in the study, 142 (40.6%) were identified as anoestrus. The average daily milk production, days in milk at artificial insemination (AI), number of AIs, and parity were 33.8 ± 6.8 kg, 152.6 ± 24.4 days, 1.3 ± 0.2 AIs, and 1.9 ± 0.8 lactations, respectively. To assess embryo survival in anoestrus dairy cows undergoing the modified DO protocol, two groups were established. The experimental group (E group, n = 74) received the GnRH agonist gonadorelin five days after TAI as part of the DO protocol. The control group (C group, n = 68) received only the DO protocol. The pregnancy rates and cumulative pregnancy rates were significantly higher in the E group (35.1% and 56.8%) compared with the C group (26.5% and 45.6%, p < 0.05). A binary logistic regression analysis indicated that the interaction between treatment and anoestrus status considerably affected the pregnancy rate (p < 0.001) and the occurrence of accessory corpus luteum (aCL, p < 0.0001). The UW-DairyRepro$ decision support tool utilized in this study, indicated that implementing this approach could increase the net present value (NPV) by USD 54.2/anoestrus cow/year.