enzymes of rumen micro-organisms. Hemicellu- 
loses are widely distributed in forages, and are 
important because they contribute a major por- 
tion of the digestible carbohydrates in the ani- 
mal diet (Maynard and Loosli 1956). 
Ash 
Almost all of the mineral content of plants 
is recovered in the ash left after ignition at 
600° C. Thus, the presence of ash indicates the 
total mineral content, but does not indicate the 
individual minerals. It is often an advantage to 
know the ash content of forages because many 
measurements of digestibility and of certain 
substances which relate to digestibility are 
made on an ash-free basis (Sullivan 1962). 
Calctum.—The ruminant animal must have 
access to adequate calcium. Calcium and phos- 
phorus compounds are the most commonly ana- 
lyzed minerals; they comprise about 90 percent 
of the mineral matter in the skeletons of live- 
stock and about 75 percent of that in their en- 
tire bodies. One-half of the minerals in milk 
are calcium and phosphorus compounds (Mor- 
rison 1957). Calcium is also an important part 
of the blood plasma where it aids in blood clot- 
ting. On western ranges, calcium supplies are 
usually ample, and may be high enough to ad- 
versely affect the metabolism of phosphorus 
(Morrison 1957). 
Phosphorus.—Phosphorus is vital in many 
body processes. It is an essential part of the 
skeleton, intracellular fluid, and compounds 
such as nucleoproteins and_ phospholipids. 
Phosphorus also is necessary in the transfer of 
energy (Anderson 1953). 
Phosphorus is deficient in many forage spe- 
cles on western and southern ranges during the 
winter. Range livestock in these regions may 
need to be fed phosphorus supplements to 
maintain adequate phosphorus levels during 
late summer to early spring. 
_A deficiency of phosphorus or a wide cal- 
cium-phosphorus ratio may retard growth, 
create a high feed requirement, and cause an 
unthrifty appearance. A desirable calcium- 
phosphorus ratio is somewhere between 1:2 
and 2:1, but ratios wider than 2:1 are permis- 
sible if sufficient vitamin D is present in the 
ration. A wide calcium-phosphorus ratio may 
prevent metabolism of phosphorus and thus 
result in a phosphorus deficiency (Maynard 
and Loosli 1956). 
Other minerals.—Sodium, potassium, chlor- 
Ine, magnesium, iron, sulfur, iodine, manga- 
nese, copper, cobalt, and zinc are necessary for 
many body processes. Some of these minerals 
function. as constituents or activators of en- 
zymes, and only very small amounts are needed. 
Many minerals, although important, are usually 
supplied in adequate amounts in common forage 
plants and are not normally reported in routine 
feed analyses. 
Vitamins 
Vitamins are organic compounds essential 
for normal functioning of the body. Their 
chemical role is largely catalytic: they usually 
form a part of or act with various enzymes, 
and only minute amounts are required (Peter- 
son and Strong 1953). The oil-soluble vitamins 
—A, D, and E—cannot be synthesized by the 
animal body, but the water-soluble vitamins— 
C, B complex, etc.—can be synthesized from 
other food constituents by rumen bacteria. 
Vitamin A and carotene.—Animals convert 
plant carotenes to vitamin A. While four caro- 
tenes in plants have vitamin A activity, only 
the beta form is a major source to the animal. 
Approximately 50 percent of the beta carotene 
in forage is converted to vitamin A by the ani- 
mal body (Anderson 1953). Although vitamim 
A is needed in only minute amounts, animals 
can store it for only relatively short periods. A 
deficiency may develop after prolonged pe- 
riods of feeding on forages devoid of green ma- 
terial. Unsuccessful reproduction, retarded 
growth, death of young, night blindness, eye 
lesions, and a general degeneration of the nerv- 
ous system are symptoms of vitamin A defi- 
ciency (Morrison 1957). 
Vitamin D.—The ruminant animal needs vi- 
tamin D, which is usually available in sun- 
cured forage or from the effect of direct sun- 
light upon the animal’s body. When young ani- 
mals are on green forage or when they receive 
too little sunlight, vitamin D deficiency may 
occur. Such a deficiency will cause rickets in 
young animals and will inhibit calcium and 
phosphorus metabolism in animals of all age 
classes (Maynard and Loosli 1956). 
Vitamin E. —One of the oil-soluble vita- 
mins, vitamin E (alpha tocopherol) is an im- 
portant component of enzyme systems and is 
important in hormone production by the pitui- 
tary, adrenal, and thyroid glands. Adult ani- 
mals rarely are affected by vitamin E defi- 
ciencies, because natural feedstuffs normally 
supply adequate quantities. Young animals, 
however, may suffer muscular dystrophy when 
on rations deficient in this vitamin. High levels 
of nitrites may result in vitamin E deficiencies. 
Vitamin E has antioxidant properties impor- 
tant in animal nutrition, since feeding vitamin 
E improves utilization of dietary vitamin A 
(Fruton and Simmonds 1953). 
Energy 
Energy is a highly significant measure of the 
nutritive value of feeds. Considerably more nu- 
triment is required to maintain normal energy 
3 
