Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2023
Publication Date: 6/1/2023
Citation: Miles, A.M., Hutchison, J.L., Van Raden, P.M. 2023. Improving national fertility evaluations by accounting for the rapid rise of embryo transfer in US dairy cattle. Journal of Dairy Science. https://doi.org/10.3168/jds.2022-22298.
Interpretive Summary: Commercial embryo transfer (ET) began in the 1970s and has become common practice in herds desiring to increase their rate of genetic progress. Trend in ET breeding event reporting do not parallel the ET calf birth rate. This discrepancy can interfere with national genetic evaluations and on-farm fertility management. Completely censoring ET-associated records is not the desired approach, as these represent the most elite animals and herds, and unreported ET could bias fertility trait evaluations in the population. We describe an edit accounting for incorrect ET reporting and explore its impact on evaluations of sire, heifer, and cow conception rates.
Technical Abstract: Dairy producers have improved fertility of their herds by selecting bulls with higher conception rate evaluations. This research was motivated by the exponential increase in embryo transfer (ET) use to 11% of recent births and >1 million total births with >5 times as many ET calves born in the U.S. in 2021 compared to just 5 years earlier. Recent records in the national database revealed that only 1% of ET calves correspond to ET breeding events (for recipients), 2% are incorrectly reported as AI, and 97% have no associated breeding event. Embryo donation events are also rarely reported . Herdyears reporting >10% of calves born by ET but less than half of the expected number of ET breeding events were removed to avoid potential biases. Heifer, cow, and sire conception rate evaluations were recalculated with this new dataset according to the methods used for the official national evaluations. The edits removed about 1% of fertility records in the most recent 4 years. Subsequent analysis showed that censoring herdyears with inconsistent ET reporting had little effect on most bulls except for the highest ranking, younger bulls popular for ET use. Improved ET reporting will be critical for providing accurate fertility evaluations, especially as the popularity of these advanced reproductive technologies continues to rise.