16 BULLETIN 873, U. S. DEPARTMENT OF AGRICULTURE. 
however, is composed. of a number of rather complex substances, 
such as protein, carbohydrates, fats, and fiber, which are not appre- 
ciably affected by the changes of ordinary air temperatures, or by 
time, as limited by the length of time hay is usually in storage. 
If the term ‘‘destroyed’’ were used in place of ‘‘lost’’ it might better 
convey the idea that a loss of dry matter does not take place as easily 
as does that of water, or at least that the conditions under which it 
occurs are different. The indiscriminate use of the term “‘lost’’ and 
a lack of knowledge of conditions under which dry matter may be 
destroyed seem to have led some to assume, in certain instances at 
least, that dry matter has been destroyed when conditions do not 
warrant such an assumption. 
The primary cause of loss of dry matter in hay is improper or 
insufficient curing of the hay before it is put into the barn or stack. 
Hay that contains too much water, either because it has not been 
sufficiently cured in the field or because it has been wet by rain, is 
liable to lose a part or even most of its dry matter later on. The loss 
of dry matter is not due merely to direct loss of water, as is some- 
times supposed, but largely to conditions arising from the mistakes 
or misfortunes of the haymaker. Hay is stored when insufficiently 
cured, either because the haymaker uses poor judgment or because 
he is unable, on account of unfavorable weather, lack of haymaking 
machinery or help, to cure his hay properly. In such cases as the 
water content is above the maximum, destruction of dry matter is 
possible. 
When wet or undercured hay is put into the barn or stack it soon 
begins to sweat and ferment, just as does properly cured hay. The 
degree of heat engendered in the fermentation of well-cured hay 
does not injure the dry matter. In the undercured or wet hay the 
temperature continues to rise until more or less of the hay is discolored, 
charred, or even burned to ashes. Such high temperatures are 
engendered primarily by the excess water in the hay, which creates 
conditions favorable for bacterial growth and chemical action, 
involving various changes in which heat is produced. In some 
instances continued cloudy, rainy, or foggy weather, by preventing 
the evaporation of water from the hay, may render conditions 
favorable for the destruction of dry matter, a situation which could 
not arise during dry, sunny weather. 
Keable and Wale * found that ‘‘newly ricked hay (clover), under- 
going a natural fermentation, soon reaches its maximum tempera- 
ture, i. e., toward the end of the first or the beginning of the second 
week after the hay was put into the rick.’”’ It was also found that a 
second fermentation occurred, beginning about three weeks after 
20 Journal Southeastern Agricultural College. Wye. No. 18, 1909, p. 52-55. 
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