107 UNEXPLAINED VARIATION IN EMBRYO FREEZER DIGITAL READOUT

Abstract

Differences among frozen embryo transfer results are often observed but are usually unexplainable. One cause of possible variability in pregnancy rates could be faulty digital readout of the biological freezer unless adequate controls are routinely used. By monitoring temperatures throughout the freezing process independently of the freezer readout, differences between the embryo freezer digital readout (EFDR) vs thermocouple (TC) and digital thermometer (DT) were observed when using a Bio Cool II Alcohol Freezer. The difference between EFDR and actual temperature (TC and DT) ranged from –4.9°C to +5.4°C. To further investigate possible causes of these differences, electrical supply to the freezer and ambient temperatures were monitored at 21 different on-the-farm locations. Ranges of voltage (117–124.4), Hz (59.96–60.00), mA (10.82–11.90) and ambient temperature (–6.1°C to +23.9°C) were recorded. However, no correlations between the EFDR and voltage (r = 0.097), Hz (r = –0.227), mA (r = 0.140), or actual temperature (r = –0.350) were found (P > 0.05). Two freezing procedures were done in unheated barn areas where the ambient temperature was –6.1°C and –4.9°C, with readout differences of +1.7°C and –0.8°C, respectively. Six of the 21 differences were ≥+2.0°C and 4 differences were ≤–2.0°C. The variable EFDR was apparently a problem within the freezer itself. In practice the real temperature (TC and DT) was used to determine the seeding temperature, therefore eliminating the chance of seeding at highly variable temperatures (–10°C to –2°C). The readout difference remained consistent throughout the freezing process and did not affect the freezing curve. It is suggested that any laboratory instrument be independently monitored to ensure quality control.