The administration of GnRH prior to TAI is done to induce a preovulatory LH surge and thus ovulation. The timing of ovulation and breeding has a significant impact on conception rates. Due to its impact, it is often worth evaluating the timing of GnRH administration is often worthwhile while evaluating the timing of GnRH administration compared to the time of insemination.  

Evaluation of the impacts on conception rate can be done utilizing conception rate reports that are grouped by the hours since GnRH administration. 

Figure 1. Conception rate by GnRH in hours (by two-hr increments) for breeding with GnRH prior (Link) 

Understanding the impact is useful to know if processes/behaviors at the farm need to be adjusted. Sometimes this is as simple as setting an initial time of GnRH administration as 3 pm, instead of it being the afternoon. Sometimes in the late afternoon, it is 1 pm because of a soccer game! 

Reporting on TAI with timing can be helpful for understanding where we are getting off on protocol. One specific example is looking at the timing by pen (Figure 2).  In this case, we are really looking for pens that are getting GnRH late because we breed those pens later in the morning but give GnRH earlier in the afternoon.  Changing the order of GnRH administration to your pens can result in more accurate timing of ovulation and see improvements in conception rates.  Alternatively, you might flip the grouping and find if varies by week, suggesting non-compliance with the schedule (Figure 3).   

Figure 2. GnRH administration by pen, using 17 hours as the cut-off for long intervals of GnRH. (Link) 

Figure 3. GnRH administration by week, using 17 hours as the cut-off for long intervals of GnRH. 

Due to its impact on conception rate, routine evaluation of GnRH administration can be warranted on dairies. Use of the reports in the figures and other variations thereof can identify the economic significance of non-compliance as well as the causes.