Dairy cattle culling patterns, explanations, and implications.

摘要

Culling patterns in the Upper Midwest and Northeast regions were examined from Dairy Herd Improvement records from 1993 through 1999. There were 7 087 699 individual cow lactation observations of which 1 458 936 were complete. A probit regression model was used to determine how individual cow and herd characteristics affected the likelihood of a cow being culled. The model predicted whether individual cows were culled each month. With a combination of observable cow and herd characteristics, as well as variables to capture state, year, and farm effects, the model was able to explain, with a 79.5 and 79.9% accuracy rate, individual cow cull decisions in the Upper Midwest and Northeast regions, respectively. Summer (-11.5% in the Upper Midwest; -6.4% in the Northeast) and fall (-18.7% in the Upper Midwest; -7.9% in the Northeast) calving vs. spring calving, higher than average milk production (-1.7% per hundredweight in the Upper Midwest; -0.5% in the Northeast), higher than average protein content (-0.2% per additional percentage milk protein in the Upper Midwest; -0.1% in the Northeast), higher milk production persistency (-2.1% per additional percent persistent in the Upper Midwest; -1.8% in the Northeast), and expansion (during the early years following the expansion) were associated with a reduced likelihood of a cow being culled. Lower than average fat content (0.04% per additional percentage butterfat in the Upper Midwest; 0.02% in the Northeast), and higher than average somatic cell count (8.8% for each unit increase in somatic cell count score in the Upper Midwest; 7.8% in the Northeast) were associated with an increased likelihood of a cow being culled. The study results are useful in describing patterns of culling and relating them to cow, herd, geographic, and time variables and can act as a benchmark for producers..