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A Method of Equalized Feeding for Studies with Dairy Cows

Laboratory of Animal Nutrition, Cornell University, Ithaca, New York

ABSTRACT

The difficulties encountered in dairy cow experiments when using the usual method of periodically adjusting feed intake to production have been discussed. It has been pointed out that the method introduces a bias into ration comparisons, and that under these conditions there is a high variability among experimental animals as regards persistency. The latter effect reduces the precision of experimental comparisons.

A method of equalized feeding is presented, which prevents biases in ration comparisons, and simultaneously increases precision by allowing more uniform persistency among animals. Essentially, the method of equalized feeding consists of periodically changing the concentrate intakes of all animals on an experiment regardless of ration, exactly the same percentage of their respective initial concentrate intakes. Meanwhile the roughage portion of the ration is maintained constant for each animal.

The method may be applied in conjunction with either the continuous or change-over types of trials. When using equalized feeding and about twenty animals, it would be expected that differences of 3.5 to 5.0 per cent could be demonstrated as significant in the continuous trial, and differences of 2.0 to 3.0 per cent in the change-over trial.

Under conditions of equalized feeding, depressing effects on production rates were noticed as early as the eighteenth week of pregnancy.