Many countries in
Europe, and Australia and Canada have adopted varying strategies for
the improvement of their dairy herds. However, the program used by
the Dairy Herd Improvement Association (DHIA) of the United States
is the most comprehensive and complete of all dairy production and
half of the cows in the country on production test are a part of
this program. Both registered and grade cows can be enrolled. In
A supervisor or
tester employed by the local or state testing association visits the
herd one day each month.
identifies all cows in the herd,
weighs and takes representative samples of the milk from all animals
in the herd for two consecutive milkings (three milkings for
herds on three times daily milking), and then combines the milk
samples and sends them to a central testing laboratory for analyses
of components such as butterfat, protein, and somatic cell count (SCC).
obtained on individual cows based on monthly and cumulative records
for milk, fat, and protein; for amount of feed, cost of feed, and
income over feed cost; and for breeding dates, calving dates, dry
dates; and other factors affecting productivity.