If you're going to expand your dairy, the bigger the better in terms of cow mortality—especially for Holsteins in the southeastern United States.
A University of Tennessee (UT)study involving 1,816 Holstein herds and 268 Jersey herds evaluated the effect of expansion on cow mortality between the years 1982 and 2005.
Holstein herds that expanded less than 30% had the highest rates of mortality, says Joan Cooper, a UT dairy scientist who worked on the study with Gary Rogers of Geno Global. "Too many of these producers expanded by overcrowding their existing facilities,” Cooper says. Such overcrowding proved the most lethal to cow survival rates. First-calf heifers were most at risk when expansions were modest, she adds.
The best survival rates in Holstein herds were when expansions were greater than 350%. Large expansions were presumably into new, state-of-the-current-art facilities.
Smaller herd sizes also were associated with lower mortality rates in Holsteins. The exception was in Holstein herds of 200 to 700 cows, which had higher rates of mortality than herds with more than 700 cows.
In the past 2 decades in the Southeast, Holstein death losses increased from 1.7% to 4% (1st lactation), from 2.1% to 5.5% (2nd lactation) and from 3.8% to 10.1% (3rd and later lactations).
In contrast, Jerseys seemed to tolerate over-crowding. Mortality rates were lowest in expansions of 100% or less. From 1982 to 2005 in the Southeast, Jersey death losses increased from 1.4% to 2.4% (1st lactation), from 2% to 4.1% (2nd lactation) and from 2.6% to 8.8% (3rd and later lactations).
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