percent sulphur, it is not likely to be deficient 
for most animals. 
Potassium functions in the same general 
way as sodium and chlorine. Rats, pigs, and 
chickens need potassium levels of approxi- 
mately 0.2 to 0.38 weight-percent of the dry 
ration. 
Iodine is necessary for proper functioning of 
the thyroid gland. Levels high enough to prev- 
ent goiter range between 0.002 to 0.004 mg. per 
kg. of body weight. Growing quail and pheas- 
ants need about 0.30 mg. per kg. of feed. 
As a constituent of hemoglobin, iron is es- 
sential for the functioning of every organ and 
tissue in the body. Rations containing 100 to 
200 mg. of iron per kg. of feed are ample for 
sheep and cattle. Chickens require about 18 
mg. per kg.; however, young turkey poults 
require about 60 mg. per kg. of feed. Iron defi- 
ciency often causes anemia. 
Copper is neccessary for hemoglobin forma- 
tion. Deficiency symptoms vary by species. Re- 
quirements are approximately 1.8 mg. per kg. 
of feed for poultry, 4 to 8 mg. per kg. of feed 
for cattle, 5 mg. per day for sheep, and 2 mg. 
per day for pigs. 
Cobalt is important in the synthesis of vita- 
min B,., which combats anemia and improves 
growth. Animals appear to need about 0.2 mg. 
per kg. of body weight daily. Deficiency symp- 
toms include anemia, loss of appetite, weak- 
ness, emaciation, and eventually death. 
Manganese is essential in reproduction and 
in bone formation. Beef cattle appear to re- 
quire about 5.4 to 9.0 mg. per kg. in air-dry 
ration, and breeding turkeys need about 33 mg. 
per kg. of feed. 
All animals require some zinc. The exact 
amount for most species is unknown, but zinc 
is rarely deficient in diets. A diet containing 
100 p.p.m. of zine alleviated the clinical symp- 
toms of deficiency in sheep. 
In the absence of specific information on the 
minor-element requirements of game, it must 
be assumed that big game need about the same 
quantities as cattle and sheep, and that game 
birds need about as much as domestic poultry. 
Vitamins 
Vitamin A.—Plants do not produce vitamin 
A, but they contain its precursor, carotene, 
which is converted into the vitamin in ani- 
mals. Much of the carotene is lost during cur- 
ing of roughage, and it is often deficient in 
late-winter food. Vitamin A can be stored in 
the liver and also as carotene in body fat. Ani- 
mals on nutritious green forage store extensive 
reserves for the winter, when the diet may be 
deficient. The rate of vitamin A storage on a 
high-intake diet can greatly exceed the rate of 
depletion on a vitamin-deficient diet. Lambs 
16 
pastured on green feed, for example, store up 
to a 200-day supply of vitamin A in their liv- 
ers. 
Vitamin A requirements listed in table 2 for 
sheep and cattle probably are about the same 
as those of big game. Game birds need rela- 
tively high levels of vitamin A (table 2), and 
high mortality of quail occurred in Texas when 
food was deficient in this nutrient (Lehmann 
1952). 
Vitamin D.—Vitamin D is formed by the ac- 
tion of radiant energy on ergosterol and cho- 
lesterol in amimals. 
The amount of vitamin D needed varies with 
the relative mineral concentrations in the diet 
and with the species. Requirements for beef 
cattle are estimated to be about 300 IU per 45 
kg. of live weight, and for sheep about 250 IU 
per 45 kg. of live weight. 
Turkeys and pheasants need more vitamin D 
than chickens. 
Vitamin D promotes retention of calcium 
and phosphorus in blood and tissue. The body 
can store some of this vitamin. 
Vitamin D is unlikely to be deficient in ani- 
mals in the open during the summer. The most 
critical time is winter, when days are short 
and cloudy, and when the sun’s rays are least 
concentrated. 
CONCLUSIONS 
Animal “nutrient requirements” are useful 
standards for selecting forage species for eval- 
uating the carrying capacity of ranges, and 
for determining the adequacy of rations for 
animal maintenance, growth, reproduction, 
and fattening. The requirements are not exact 
because they are influenced by many ever- 
changing factors, such as size, activity, age, 
and condition of the animal; quality of food; 
season of use; and weather. 
Digestible energy is the most common defi- 
ciency in the diet of range herbivores. Reason- 
ably good energy standards have been devel- 
oped for livestock under controlled conditions, 
but similar information is generally unavaila- 
ble for wild ruminants. In the future the em- 
phasis in nutrition research should be to estab- 
lish energy requirements under range condi- 
tions. 
Even though much research has gone into 
finding the animal requirements for protein, 
calcium and phosphorus, the standards for 
range animals, particularly wild ruminants, 
are not well established. In some cases the 
minimum requirements seem inconsistent with 
the quality of forage ingested on ranges sup- 
porting healthy animals. 
Game birds and small mammals generally 
have higher requirements than large rumi- 
nants for protein, phosphorus, and calcium, 
