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TABLE 1.—Required content of major nutrients in the feed of selected classes of cattle and 
sheep (NAS-NRC 19638, 1964) 
Beef Cattle 
Class, size, and rate of gain Protein DP? DE#* TDN* Ca P 
Percent Keal./lb. © Percent________- 
Steers and heifers, normal growth: 
400 lb.; 1.6 lb./day 11.7 7.0 1,050 53 0.29 0.21 
800 lb.; 1.2 lb./day 7.8 4.7 1,000 50 18 15 
Wintering weanling calves: 
400 lb.; 1.0 lb./day 10.3 6.2 1,000 50 27 21 
600 lb.; 1.0 lb./day 951! 5.5 1,000 50 .20 16 
Wintering Seanlinie cattle, 
800 lb.; .7 lb./day 7.5 4.5 1,000 50 18 17 
Wintering pregnant heifers, 
900 lb.; .8 lb./day 7.5 4.5 1,000 50 16 15 
Wintering mature pregnant cows: 
800 lb.; 1.5 lb./day 7.5 4.5 1,000 50 16 15 
1,000 lb.; .4 lb./day 7.5 4.5 1,000 50 16 15 
1,200 lb.; —.5 lb./day 7.5 4.5 850 43 16 15 
Cows nursing calves, first 4 mos. 
900-1,100; .0 lb./day 8.3 5.0 1,200 60 .24 18 
Sheep 
Nonlactating, first 15 weeks of gestation: 
120 lb.; .07 lb./day 8.0 4.4 1,000 50 24 19 
160 lb.; .07 lb./day 8.0 4.4 1,000 50 .20 16 
Last 6 weeks of gestation: 
120 lb.; .387 lb./day 8.4 4.6 1,040 52 24 18 
160 lb.; .87 lb./day 7.8 4.3 1,040 52 22 16 
First 9 weeks of lactation 
100 lb.; —.08 lb./day 8.7 4.8 1,180 59 30 22 
160 lb.; —.08 lb./day 8.0 4.4 1,100 55 27 .20 
Replacement lambs and yearlings: 
80 lb.; .20 lb./day 8.7 4.8 1,000 50 .20 18 
120 lb.; .07 lb./day 7.0 3.9 1,000 50 .20 18 
Fattening lambs, 
70 lb.; .40 lb./day 11.0 6.1 1,160 58 21 18 
* Based upon air-dry feed containing 90 percent dry matter. 
* Digestible protein: total protein assumed 60 percent digestible for cattle and 55 percent for sheep. 
*One pound total digestible nutrients (TDN) assumed equivalent to 2,000 keal. of digestible energy (DE). 
requirements in percentages of digestible nutri- 
ents in the diet. These have been calculated by 
NAS-NRC from daily nutrient requirements 
and assumed levels of feed intake and digest- 
ibility. Their alternative standards for daily 
requirements of nutrient weight are appro- 
priate for computing supplemental rations. 
Energy 
Supplementing range with energy feeds 
seems rarely justified. Although lack of energy 
is considered the most common manifestation 
of nutritional deficiency of livestock (NAS- 
NRC 1963, 1964), this can result from limi- 
tations in either the amount or the quality 
of feed. From the viewpoint of supplementa- 
tion, we are concerned primarily with forage 
quality because it can be assumed that quantity 
can best be provided through grazing manage- 
ment. 
Energy feeds might be considered as substi- 
tutes rather than supplements for range forage 
because energy is the major component of the 
animal diet. However, the practice of provid- 
ing energy feeds to carry livestock through 
emergency periods permits practical utilization 
of range during otherwise hazardous seasons. 
Appropriate levels of emergency supplements 
are shown in standards for wintering livestock 
(Morrison 1954, NAS-NRC 1968, 1964). For 
example, the daily energy requirements for 
maintaining weight of a pregnant, 1,000-pound 
cow could be met by the equivalent of 11 
pounds of corn or 17 pounds of good alfalfa 
hay daily. Pelleted commercial feeds will likely 
be fed on range where hay is not readily acces- 
sible. A common practice is to feed individuals 
or lots of animals as necessary to keep them in 
fair condition. 
Western range forage generally does not 
seem critically deficient in energy; however, 
specific information is scarce. Even during 
winter, when forage values are lowest, West- 
ern grassland ranges seem to maintain live- 
stock adequately with only protein supplement 
(Smith et al. 1967). Grasses of Western semi- 
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