In a national survey of US dairy operations, 1685 dairy operations
reported 47057 new dairy heifers (either births or acquisitions) and 4427
deaths
(9·4%) of preweaned dairy heifer calves over a 3 month
period. Stepwise logistic
regression was used to identify management practices associated with high
mortality
among preweaned heifers in dairy operations where at least three dairy
heifer calves
were born alive or moved on to the operation. Analysis was done twice:
once by
separating all operations by size into high or low mortality; again using
only
operations with <2 and >10% mortality to eliminate dairy operations
with
intermediate levels of mortality from the comparisons. Results were similar.
Dairy
operations in the West were more likely to fall in the high mortality category
than
dairy operations in the rest of the country. In addition, the
following dairy operation
characteristics were associated with high death levels in both models:
rolling herd
average milk production <7710 kg, preweaned heifers placed in groups
of seven or
more, a male having primary responsibility for the care and feeding of
preweaned
heifers, calves not receiving hay or other roughages until >20 d
old, calves fed on
mastitic or antibiotic milk after colostrum and calves not given whole
milk after
colostrum.