After a Decade of Genomic Testing, Are Milk Yields Being Impacted?

Abstract

Over the past decade, genomic testing has transformed the U.S. dairy cattle genetics market by allowing breeders to identify high-performing bulls at birth, sharply reducing generation intervals and increasing the rate of genetic improvement in milk production traits. Using data on dairy bull genetics, national and state-level milk yields, and herd characteristics from 2000 to 2020, this article documents a clear structural break around 2010, the predicted genetic potential for milk yield of dairy bulls more than doubled in its rate of growth following the adoption of genomic testing, while the number of bulls on the market tripled and the age at which bulls were first sold fell dramatically. Despite this rapid acceleration in genetic potential, realized milk yields at the national level have continued to grow at roughly the same pace as before genomic testing and have even slowed in recent years. Disaggregated evidence shows modest gains concentrated in states with smaller average herd sizes, suggesting heterogeneous returns to genetic improvement across production systems. We discuss several explanations for this divergence between genetic potential and realized outcomes, including genotype-by-environment interactions, differences in farm management and scale, data limitations in genetic evaluations, and environmental stressors. The findings highlight an important puzzle in agricultural productivity growth and underscore the need for better data on genetic adoption, costs, and farm-level responses to fully understand the impacts of genomic innovation in dairy production.