254 Western Live-stock Management 
eral wear of the body tissues. They do not need the large 
amount of net energy which is required when the horse is 
doing physical work. Since the body has already attained 
full growth, protein and mineral matter will be needed only 
to make up for the loss due to the natural wear and waste 
of the body tissues, while the larger part of the need will 
be carbohydrates and fats, which are heat-producing. 
Such bulky feeds as straw and the coarser hays, that would 
not be suitable for work horses, may be used to advantage 
in this case. It has been found that the energy required 
for mastication and digestion of wheat straw is about 
equal to the total energy of the feed. Therefore, the 
energy which can be derived from wheat straw and con- 
verted into actual work is very small, in fact so small that 
such feeds have little value for hard-working horses. In 
the case of an idle horse, however, where the chief need 
of the body is for heat-producing feeds, it is found that 
this energy from the wheat straw, which was used up in its 
own digestion and assimilation, is converted finally into 
heat, and thus serves to maintain the temperature of the 
body. Thus it is that these foods with very small amount 
of net energy may be used to advantage in maintaining 
idle horses. Another point in favor of using bulky feeds 
for this purpose is that the total amount of digestible 
nutrients required to maintain a horse in idleness is com- 
paratively small, and if given in concentrated form, 
such as some of the rich grains, the horse will not produce 
enough bulk to satisfy the appetite, and would be very 
ravenous and not thrifty. Furthermore, this small 
quantity of rich food would be likely to cause digestive 
disorders. 
The feeding of the cheaper feeds to idle horses has 
another decided advantage. Work horses are not expen- 
