64 Animal Husbandry 
Since the demands on the body for maintenance are largely for 
the production of muscular energy and heat, nine-tenths or more 
of the maintenance ration may consist of carbohydrates. - 
119. Productive rations. — Productive rations may be looked 
upon as made up of two parts: that which is needed to maintain 
the animal, and that which may be applied to production after 
the bodily needs have been sup- 
plied. It is the food consumed and 
digested in excess of the amount 
required for maintenance that en- 
ables the animal to produce. The 
question, then, is as to the quan- 
tity of food the animal will con- 
sume and make sufficient returns 
for in production. While it is 
true in a sense that the amount 
Fic. 34. —Belgian stallion. of production is in proportion to 
the amount of food assimilated 
in excess of that required for maintenance, it is only within 
rather narrow limits that this relation holds strictly true. The 
individuality of the animal plays an important part. All 
farm animals will eat and digest more food than is required 
for maintenance, but the amount of product that comes 
from this excess of food is variable, and in many cases this 
makes the difference between a profitable and an unprofitable 
animal. 
120. Feeding-standards for farm animals. — A feeding-stand- 
ard is a rule to which all rations should conform for a given pur- 
pose. The Germans have done much work in establishing such 
standards, which have long been in general use as guides in com- 
puting rations for farm animals. More recently, Kihn, Kellner, 
Armsby, and others, working with the energy value of food, have 
suggested feeding-standards based upon the amount of energy 
required to yield a given product. 
