ANIMAL PRODUCTION AND FORAGE QUALITY 
Definition and Components of Forage Quality 
DONALD R. DIETZ? 
The quantity of forage produced, measured 
by green or dry weight yield per acre, has long 
been the criterion of the value of a range for 
livestock, wildlife, or both. Only in recent 
years have the relationships between forage 
yield and quality and animal response been 
closely studied and partially understood (Sell 
et al. 1959). Several authors (Savage and 
Heller 1947; Cook and Harris 1950; Leopold 
1950) have indicated that forage quality may 
be as important a factor as forage quantity in 
relation to animal carrying capacity. 
Many of the terms used in forage quality 
studies will be defined in this paper, and some 
of the aspects and components of forage qual- 
ity will be discussed. The discussion will be 
limited principally to forage quality as it re- 
lates to the ruminant animal on rangelands. 
DEFINITION OF FORAGE QUALITY 
Forage quality has been defined in many 
ways, but usually in relation to some animal 
response such as feed intake, weight gain, or 
production of milk or wool. Other terms asso- 
ciated with animal response, but which provide 
a measure of forage quality, are palatability, 
nutritive composition and digestibility, gross 
and digestible energy, and ruminal end prod- 
ucts. Forage quality has also been estimated 
from such plant attributes as leaf-to-stem ra- 
tios and stages of plant maturity (Lucas 1963). 
Other indices of forage quality are: (1) Visual 
estimate of quality such as Federal hay grades, 
(2) leaf content of forage, and (3) botanical 
composition, particularly legume content (Reid 
et al. 1959). 
Nearly all authors agree that high-quality 
forage for a ruminant animal will possess the 
following characteristics: (1) High palatabil- 
ity to the animal, with resultant high feed in- 
* Principal Wildlife Biologist, Rocky Mt. Forest and 
Range Exp. Sta., USDA Forest Serv., located at Rapid 
City, S.Dak., in cooperation with the S.Dak. Sch. of 
Mines and Technol. Central headquarters for the sta- 
tion is maintained at Fort Collins, Colo., in cooperation 
with Colo. State Univ. 
take, (2) optimum levels of various nutrient 
components in proper ratios during period of 
animal use, (8) high apparent digestibility of 
the nutrient components with an optimum 
ratio of nitrogenous to nonnitrogenous compo- 
nents, (4) volatile fatty acids in optimum pro- 
portions for efficient energy production, (5) 
adequate levels of minerals, vitamins, and 
trace elements, and (6) efficient convertibility 
into components necessary for the animal body 
over sustained periods. 
The range and wildlife scientist has several 
techniques available for evaluating forages on 
rangelands. Some of these are: (1) Chemical 
analyses, (2) animal feeding trials, (8) i 
vitro rumen techniques, and (4) grazing trials. 
The terms used in these techniques will be re- 
viewed briefly. 
DESCRIPTION AND IMPORTANCE OF 
NUTRITIONAL MEASUREMENTS 
Chemical Constituents 
Crude Protein 
The term crude protein represents both pro- 
tein and nonprotein nitrogen. It is calculated 
by multiplying the nitrogen percentage of feed 
by a factor, usually 6.25. True proteins are 
large, complex molecules composed of up to 22 
amino acids. While it is true the test for crude 
protein does not indicate the kinds and 
amounts of amino acids present, no evidence 
indicates that ruminant animals require partic- 
ular amino acids. Digestion in the rumen Is a 
microbiological process, and amino acids are 
synthesized as needed (Sullivan 1962). Urea or 
other protein substitutes may equally well 
provide nitrogen for amino acid production. 
Protein is considered the most important nu- 
trient to the animal. A serious deficiency re- 
sults in failure of the body to maintain itself, 
while even a slight deficiency adversely affects 
reproduction, lactation, growth, and fattening 
processes (Morrison 1957). 
