INFLUENCE OF STAGE OF LACTATION. 147 
The cows received daily on an average 6.011 pounds of 
digestible matter available for product, and yielded daily 
1.245 pounds of butter fat. The data already submitted 
shows that it requires 6.25 pounds of net digestible matter 
to a pound of butter fat, and upon this basis the nutriment 
provided daily was only enough for a daily yield of .962 of 
a pound butter fat, while the average daily excess yield per 
cow was .283 of a pound. Since the daily average loss in 
body weight per cow was 2 pounds, the daily compensatory 
yield by virtue of decrease in live weight was at the rate of 
.14 of a pound of butter fat per pound of decrease in weight 
of body, being a sacrifice of 7 pounds of live weight to 1 
pound of butter fat vielded in excess of the yield provided 
for in the ration. 
The following deductions are made from the data sub- 
mitted: 
1. During the early stages of the period of lactation 
cows lose rapidly in body weight; of 15 cows the average 
decrease per cow the first week was 49 pounds, and during 
56 days there was a daily average loss per cow of 2 pounds. 
2. During the time when the decrease in body weight 
takes place cows yield dairy product in excess of theamount 
provided for by the food consumed; the excess of yield de- 
pending upon the rate of loss in weight of body, in some in- 
stances it is more than twice the amount provided for by the 
available nutriment. 
3. The excess yield of dairy products gradually decreases 
until about the 11th week when an equilibrium generally 
obtains between the nutriment consumed and dairy products 
yielded, though in this respect cows differ; those of a pro- 
nounced dairy temperament taking less time, while those 
not strong in dairy temperament decrease more slowly in 
weight and require more time to reach normal work in milk 
production. Before such equilibrium is reached the body fat 
and possibly other substances contribute directly or in- 
directly to product. 
4. The normal net nutriment requirements to a pound 
of butter fat is approximately 6.25 pounds, with a slight in- 
crease by cows yielding milk containing a low per cent butter 
