in these experiments was to use the largest practicable quantity of 
the new feed. While the protein content of the rations varied 
somewhat, care was taken to have the minimum well above the 
quantity generally regarded as sufficient. A certain number of 
pounds of concentrates was fed for each pound of butterf at produced, 
the adjustment being made every 10 days. 
All the milk was weighed as soon as drawn, and composite samples 
for two or more days during each 10-day period were taken for 
butterfat determinations. Body weights were taken at the begin- 
ning and end of the experimental periods for at least three consecu- 
tive days and as often at other times as necessary to control the 
live weights so that the gains would be approximately the same for 
both groups at the conclusion of the experiment. 
- In feeding experiments it is rather difficult to control all the 
disturbing factors so that a direct comparison can be made between 
two feeds at the end of the experiment. Usually there are at least 
three variable factors — milk, butterfat, and body weight. Pro- 
vided the experiment runs for a sufficient length of time, the body 
weights can usually be adjusted by raising or lowering the quantities 
of one or both of the two feeds being compared. Owing to the 
variation in the butterfat content of milk it is evident that the 
more accurate basis of calculation is the pounds of butterfat rather 
than the pounds of milk. 
After considerable thought it was decided to feed the two groups 
of cows in these experiments so that not only would the gains in body 
weight at the conclusion of each experiment be comparable, but 
each group would also have received the same amounts of feeds, 
other than those being compared, for each pound of fat produced. 
In this way a direct comparison of the two feeds on the basis of 
butterfat production was made possible. 
FISH MEAL COMPARED WITH COTTONSEED MEAL 
The fish meal used in this experiment was prepared under the 
direction of F. C. Weber, Bureau of Chemistry. It was made from 
the waste in the canning of sardines by pressing out most of the oil 
and then drying and grinding the residue. The fish meal was fed to 
six cows for two periods of 70 days each in comparison with cotton- 
seed meal. The other concentrates used in the ration were equal 
parts of corn meal and wheat bran. Alfalfa hay was fed to each cow 
at the rate of 6 pounds a day with as much corn silage as would be 
consumed without waste. Fish meal and cottonseed meal were 
each supplied at the rate of 3 pounds per cow daily until near the 
end of the experiment, when it became evident that the fish meal 
was superior to the cottonseed meal. The allowance of fish meal was 
then reduced and that of cottonseed meal increased for the purpose 
of controlling the live weight. 
Table 1 gives the analyses of the feeds used in this experiment; 
Table 2 shows the production, feed, and gain in body weight; and 
Table 3, the ratio of feed consumed to butterfat produced. 
