Cows, sheep, and large wild ruminants may 
have similar abilities to digest common rations 
even though their food selectivity may differ. 
White-tailed deer and mule deer of North 
America (Short 1963), roe deer of Eurasia 
(Briiggemann et al. 1965), and several of 
the African antelope species probably digest 
fibrous foods poorly and may suffer when only 
fibrous forages exist on a range. Hungate 
(1966) mentions some differences in rumen 
fermentation rates among herbivores; these 
differences could affect forage digestion and 
range utilization. For mule deer, the available 
energy in a feed is inversely related to its cel- 
lulose content (Short 1966). 
Horselike animals digest somewhat less food 
than ruminants. The difference is due largely to 
lower efficiency in digesting fiber, nitrogen-free 
extract, and fat components (Morrison 1950). 
Swinelike animals (except perhaps the hippo- 
potamus) digest fiber even !ess efficiently than 
do horses. 
Large rodents and lagomorphs are less 
efficient than ruminants in the digestion of 
fiber, and commercial rations for them fre- 
quently contain only 9 to 18 percent fiber 
(NAS-NRC 1962). 
PROTEIN 
Protein is essential for growth, weight gain, 
appetite, milk secretion, and regular oestrus. A 
liberal continuous supply is needed throughout 
life. When protein intake exceeds body needs 
of adult animals, nitrogen tends to be wasted 
since it can only be stored in very limited 
amounts. Therefore, protein is an expensive 
source of energy. During rapid growth, the 
body can utilize much more protein than the 
minimum requirement. The daily requirement 
increases with age and size, at least during 
early growth, but it decreases per unit of 
weight and in relation to the energy require- 
ment (Maynard and Loosli 1956). 
Protein requirements included in most live- 
stock feeding standards were determined from 
feeding trials (table 1). They generally show 
that 0.27 kg. of digestible protein per 45 kg. of 
BW is sufficient for cattle and sheep. 
In NAS-NRC standards, a digestion coeffi- 
cient of 55 percent is used to calculate digesti- 
ble protein from total protein. Perhaps the 
conversion factor should be less for range cat- 
tle and sheep because of the low protein digest- 
ibility of poor-quality range forages. 
Protein requirements of wild animals are 
probably at least equal to those of domestic 
species. If crude protein levels in deer forage 
fall below 6 to 7 percent, rumen functions are 
seriously impaired (Dietz 1965). In Missouri 
deer fed diets containing 7-percent protein de- 
veloped slower and had poorer breeding condi- 
tion and fawn survival than deer fed more 
protein (Murphy and Coates 1966). In Michi- 
gan a diet containing 12.7 percent crude pro- 
tein did not permit maximum weight gains in 
male fawns, but it was adequate for female 
fawns (Ullrey et al. 1967). 
Dietary protein levels for white-tailed deer 
have been suggested as 13 to 16 percent for op- 
timum growth and as 6 to 7 percent for main- 
tenance (French et al. 1955). On southern 
ranges during most of the year, the protein 
content of browse is below the level suggested 
for deer growth (Blair and Halls 1968; Halls 
et al. 1957). Requirements for game birds are 
higher than for deer, ranging up to 28 percent 
for growing bobwhite quail (Nestler 1949a). 
For omnivorous species such as wild pigs, and 
most rodents, a diet which encourages healthy 
growth must have a protein content of approx- 
imately 15 percent (Wackernagel 1966). Ac- 
cording to NAS-NRC (1962), large rodents 
and lagomorphs require protein levels of 15 to 
20 percent for growth and reproduction. 
WATER, MINERALS, AND VITAMINS 
Water 
Water is necessary in transportation of 
metabolic products, in secretion and excretion, 
in regulation of body temperature, and in 
many other body processes. 
Requirements for animals may be satisfied 
through free water, dew, water in feed (succu- 
lence), and metabolic water. Consumption by 
animals varies widely and depends on such fac- 
tors as temperature, rainfall, activity, age, 
stage of production, respiratory rate, fre- 
quency of watering, consumption of feed, plane 
of nutrition, and composition of feed. The im- 
mediate effect of water restriction is to lessen 
food consumption and thus reduce growth and 
food efficiency (Crampton and Lloyd 1954). It 
is best to give domestic animals free access to 
all the water they desire. 
Wild species vary widely in their water re- 
quirements (Leopold 1947). Eastern white- 
tailed deer require drinking water occasion- 
ally; nursing females need it daily. Western 
races of white-tails apparently can subsist on 
succulence alone. Mule deer can subsist and 
fawn on succulence alone. Does search for 
water during fawning, and all mule deer seek 
it after frost reduces succulence. Elk and ante- 
lope have water needs similar to those of mule 
deer; they drink regularly when possible, but 
they can subsist and reproduce on succulence 
alone. These animals may need drinking water 
during droughts, when succulence is reduced. 
Birds need less water than mammals and are 
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