Abstract
Social dominance is present in dairy production systems and affects performance, but it is difficult to measure. Latency to first meal after feed delivery may serve as a quantifiable phenotype for social dominance, given that dominant cows typically eat first. The goal of this study was to estimate the genetic variability of latency to first meal and evaluate its association with feed efficiency and feeding behavior in dairy cows. Data consisted of 6 million bunk visits from 1,770 mid-lactation Holstein cows collected from 2009 to 2024 at the University of Wisconsin-Madison using a roughage intake control system. Latency to first meal was calculated as the time it takes for a cow to access the feed following the feed delivery. The statistical model consisted of a repeatability animal model, with lactation and DIM as fixed effects, and cohort, animal, and permanent environment as random effects. Genetic parameters for latency to first meal were estimated using daily records and weekly averages. Heritability and repeatability of latency to first meal using daily records were 0.08 ± 0.01 and 0.22 ± 0.01, respectively. Heritability and repeatability of latency to first meal using weekly averages were 0.17 ± 0.03 and 0.43 ± 0.01, respectively. Genetic correlations between weekly averages of latency to first meal and DMI, milk energy, metabolic BW, and residual feed intake were -0.03 ± 0.08, -0.12 ± 0.08, 0.10 ± 0.06, and -0.08 ± 0.10, respectively. Latency to first meal was negatively correlated with number of visits at the feed bunk per day (-0.65 ± 0.06) and total duration of visits (-0.58 ± 0.05). Latency to first meal was positively correlated with duration of each visit (0.39 ± 0.07), intake per visit (0.65 ± 0.06), and feeding rate (0.51 ± 0.07). Overall, cows with longer latencies to eat had fewer but longer bunk visits, greater intake per visit, and ate at a faster rate. Latency to first meal may be a quantifiable phenotype for social dominance; it is both heritable and repeatable and is not correlated with feed efficiency.