for other classes of cattle and sheep when it 
falls below 0.15 to 0.18 percent (NAS-NRC 
1963 and 1964). A deficiency results in lowered 
appetites, a reduced rate of gain and milk 
production, and reduced efficiency of feed utili- 
zation—particularly of protein. Phosphorus 
deficiency is common in mature grass forage on 
western ranges (Morrison 1954; NAS-NRC 
1963) and is nearly universal on southern and 
southeastern ranges (Duncan and Epps 1958; 
Halls et al. 1957). 
Considering the possible benefits and low 
cost, supplementation appears justified when 
phosphorus deficiency is likely or suspected. 
This will include supplementation in fall and 
winter on most western ranges, and yearround 
on southern ranges. Total requirements are 
only 10 to 15 grams per day (0.7 to 1.0 pound 
per month) for range cattle, and 3 to 4 grams 
per day (0.2 to 0.3 pound per month) for 
sheep; lactating animals require about twice 
these amounts. 
Common sources, and their phosphorus con- 
tent, are: Steamed bonemeal (8-18 percent), 
defluorinated rock phosphate (9-21 percent), 
dicalecium phosphate (18 percent), diammon- 
ium phosphate (23 percent), and sodium phos- 
phate (12 and 22 percent). The last source is 
completely soluble and can be added to drink- 
ing water. 
Although livestock tend to satisfy their 
phosphorus requirements when bonemeal or 
other phosphorus sources are offered free 
choice, salt is commonly added as about one- 
third of the mineral mixture. To assure ade- 
quate consumption in the Southeast, molasses 
(4 to 8 percent) and cottonseed meal (4 to 6 
percent) are added along with salt (30 to 35 
percent) to the phosphorus source (50 to 60 
percent) and minor elements (Cunha et al. 
1964; Hughes and Southwell 1963). 
Minor Elements 
Iodine deficiency areas. occur locally 
throughout the Northwest, the Dakotas, Mon- 
tana, Colorado, Utah, Nevada, and Idaho 
(NAS-NRC 1964). In these areas iodized salt 
(0.01 percent potassium iodine) is recom- 
mended to avoid possible losses in lamb and 
calf crops. 
Other important minor element deficiencies 
for range livestock are limited to the South Al- 
tantic and Gulf Coast areas, principally Flor- 
ida (Halls et al. 1964). Iron, copper, and cobalt 
are included in recommended mineral mixtures 
as standard practice in Florida, and are often 
included on other southern ranges. To supply 
these elements, a typical mineral mixture for 
beef cattle in Florida will contain about 3 per- 
cent red oxide of iron, 0.6 percent copper sul- 
fate, and 0.1 percent cobalt carbonate; most of 
76 
the mixture is a phosphate source and salt 
(Cunha et al. 1964). 
RESEARCH NEEDED 
Supplementation of range diets will become 
more effective and profitable as knowledge of 
range nutrition is accumulated. Some of the 
important research challenges in range nutri- 
tion are outlined by Harris (1968). Besides de- 
velopment of better techniques for studying 
nutrition on the range, and for measuring the 
nutritive status of range animals, there are 
challenging possibilities for improving utiliza- 
tion of range forage. With better understand- 
ing of the symbiotic relations between rumen 
microorganisms and the host animal, it may be 
possible to create an environment in the rumen 
that would permit more complete or rapid uti- 
lization of the polysacchoride energy in range 
forage, and to convert some of the indigestible 
fiber into animal tissue and milk. New nitrogen 
supplements are needed to replace expensive 
protein feeds, such as soybean meal, and also 
to provide a sustained supply to rumen mi- 
croorganisms under range conditions where it 
is impractical to supplement frequently. This 
would permit long-term supplementation with 
a minimum of livestock handling and cost. An 
example is the use of sustained-release pellets 
to supply cobalt in Australia. 
One new source of nonprotein nitrogen that 
shows promise is biuret, a condensation prod- 
uct of urea. It releases nitrogen in the rumen 
more slowly, and is less toxic and more palat- 
able to livestock than urea. It was more effec- 
tive and more profitable than urea and cotton- 
seed meal for summerlong supplementation of 
crested wheatgrass range in Oregon (Raleigh 
and Turner 1968). 
SUMMARY 
Specific needs for supplementing range for- 
age are not clear because information on diges- 
tible nutrients in the heterogeneous and varia- 
ble range forages is scarce. Only general infer- 
ences can be drawn from fragmentary data 
and indirect evidence. Deficiencies are most ob- 
vious on pineland ranges of the South (includ- 
ing the Southeast). 
Under characteristic range livestock opera- 
tions, supplemental feeding is not always the 
most profitable approach to overcoming defi- 
ciencies in range diets. Besides adapting the 
livestock operation to the kind of range availa- 
ble, alternatives for providing adequate diets 
and minimizing supplementation include: (1) 
Grazing available range types at optimum sea- 
sons, and at rates that provide ample quanti- 
ties of forage; (2) improving the botanical and 
chemical composition by range seeding, burn- 
