Ruminant Nutrition for Graziers

Ruminant Nutrition
for Graziers
A Publication of ATTRA - National Sustainable Agriculture Information Service • 1-800-346-9140 • www.attra.ncat.org

By Lee Rinehart Cattle, sheep and goats have the ability to convert plant carbohydrates and proteins into available
NCAT Agriculture nutrients for human use, making otherwise unusable land productive. However, proper care of the
Specialist land and its grazing animals requires a sound understanding of ruminant nutrition. This publica-
©2008 NCAT tion provides managers with tools and references to consider biological and climatological variables
and make decisions that ensure the ecological and economic viability of a grass-based ruminant
livestock operation.
Contents
Introduction ..................... 1
The Value of Grassland
Agriculture ........................ 2
Ruminant Physiology .... 4
Nutrient Requirements
of Grazing Livestock........5
Forage Resources and
Grazing Nutrition ...........11
Matching Nutritional
Requirements of
Livestock to the Forage
Resource ............................13 Cattle. Photo courtesy of NRCS.
Supplementing Protein
or Energy: When is it
Necessary? ........................14
Forage Sampling and
Production (Yield)
Estimates............................15
Plant Toxicity and
Grazing-Related
Disorders............................16
Grazing
Management ...................16
References.........................17 Sheep. Photo by Linda Coffey, NCAT. Goat. Photo courtesy of USDA.
Resources ..........................18

Introduction This publication covers the basics of animal
nutrition from a grazing perspective. Much of
Grazing animals are very important to
what we understand about livestock nutrition
agriculture. Of course, they provide meat, has been developed from studies and expe-
milk, and fi ber. But grazing animals also rience with confinement feeding operations,
ATTRA—National Sustainable
Agriculture Information Service
can be incorporated into a crop rotation where concentrated nutrients in the form of
is managed by the National Cen- to take advantage of nutrient cycling. They grain, oilseed products, and harvested for-
ter for Appropriate Technology
(NCAT) and is funded under a can be utilized to control weeds or to ages are delivered to animals in a drylot.
grant from the United States harvest crop residues. Grazing animals These types of practices leave out many of
Department of Agriculture’s Rural
Business-Cooperative Service. can also be an added source of income, the biological and climatological variables
Visit the NCAT Web site (www.
ncat.org/sarc_current. diversifying farm enterprises and thereby that accompany grazing situations: plant
php) for more informa- rendering a farm more sustainable from an species, forage stage of maturity, soil fertil-
tion on our sustainable
agriculture projects. economic point of view. ity and water holding capacity, annual and

seasonal precipitation and mean temper- shrubs, trees) are not readily usable (from a
ature, etc. As they plan for the nutritional digestive standpoint) by humans.
needs of their grazing animals, graziers need
However, grassland ecosystems (both
to take each of these variables into consid-
rangeland and temperate grasslands) pro-
eration. This publication provides livestock
duce plant materials that are highly digest-
managers with the tools and references to
consider all the variables and make informed ible to ruminant animals. Ruminant refers
decisions that ensure the ecological and eco- to grazing animals that have the ability to
nomic viability of a livestock operation. digest and metabolize cellulose, or plant
fi ber, and ferment it to form the volatile
A ranching operation can appropriately fatty acids and microbial proteins that the
be thought of as a forage production and animal can then digest and use. This is of
utilization enterprise. Ranchers are in the particular importance to the sustainability
business of converting sunlight, water, and of agricultural production systems because
carbon dioxide into a high-quality human grasslands and rangelands have the capac-
food source. (Lalman, 2004a) Grasslands ity to produce millions of tons of this energy
and rangelands occupy a large proportion source. Grazing of native and introduced
of the U.S. land area. These ecosystems are forages on grasslands and rangeland thus is
naturally able to capture sunlight and con- a very efficient way of converting otherwise
vert it into food energy for plants. Humans non-digestible energy into forms available
have harvested plant energy for thousands for human use: milk, meat, wool and other
of years—since the beginnings of agricul- fibers, and hide.
ture. Literally millions of tons of plant-
derived food energy is harvested off arable
lands each year in the United States. But The Value of Grassland
most of the land in the U.S., and indeed Agriculture
in most countries of the world, is not till- Forages are plants, either wild or tame, that
able and is considered rangeland, forest, or are consumed as livestock feed. Grasses,
desert. These ecosystems can be very pro- clovers and other forbs (broadleaf vascular
ductive from a plant biomass perspective, plants), shrubs, and even some trees serve as
but since they are generally non-farmable, forage for livestock, depending on the ecol-
the plants they produce (grasses, forbs, ogy of the region. Arable land in the United
States, or land that is capable of being culti-
vated, accounts for only forty-three percent of
Seven Principles of Ruminant Nutrition the country’s agricultural area (FAO, 2002).
Arable cropland can be rotated into pasture
1. Ruminants are adapted to use forage because of microbes in their
to take advantage of the soil-building char-
rumen.
acteristics of perennial grass ecosystems.
2. To maintain ruminant health and productivity, feed the rumen Also, perennial grasses tend to positively
microbes, which in turn will feed the ruminant. affect water quality by serving as buffers in
3. Ruminant nutritional needs change depending on age, stage of riparian zones and increasing the water-hold-
production, and weather. ing capacity of soils. Perennial grasses and
4. Adequate quantities of green forage can supply most —if not all— forbs as a component of annual cropping
the energy and protein a ruminant needs. systems also help to reduce fuel and chemi-
cal use, allowing some fields to be in pas-
5. Forage nutritional composition changes depending on plant
ture or hayfield for several years between
maturity, species, season, moisture, and grazing system.
annual crop rotations.
6. Supplementation may be necessary when grass is short, too
mature, dormant, or if animal needs require it (i.e., high-producing In North America, more than 50 per-
dairy animal). cent of the land area is rangeland and
thus potentially grazable. The topogra-
7. Excessive supplementation may reduce the ability of the rumen
microbes to use forage. phy, soil characteristics, and water avail-
ability in these ecosystems usually limit
Page 2 ATTRA Ruminant Nutrition for Graziers

ruminant livestock and wildlife, performing
Soil Building Characteristics of
Grassland Ecosystems symbiotic duties within the animal’s body.
Animals occupy a niche and complete the
Pastures help to increase organic matter and nutrient cycle by returning up to 90 percent
humus in the soil, which results in:
of ingested nutrients back to the soil in the
• Granulation of soil particles into form of feces, urine, and their own bodies
water-stable aggregates after death. Humans play an important role
• Decreased crusting in this system as well. We engage in agri-
• Improved internal drainage culture and derive food and fiber from the
• Better water infiltration system for our consumption.
• Fixation of atmospheric nitrogen Cattle, sheep, and goats have the ability to
• Release of bound nutrients convert plant carbohydrates and proteins
• Increased water and nutrient stor-
into available nutrients for human use,
age capacity and therefore render productive vast por-
tions of otherwise unusable land. Grass-
Source: Beetz, 2002
lands offer humans a nutritious supply of
meat and milk. Many farmers and ranch-
the kind of agriculture that can be devel- ers have changed production practices
oped on them to the grazing of livestock. to take advantage of this natural process,
Livestock management on arid range- bypassing the energy intensive grain-fed
lands has been extensively addressed by operations that have dominated Ameri-
Allen Savory and Jody Butterfield of Holis- can livestock production for the past sev-
tic Management International (www.holistic eral decades. Products from grass-finished
management.org). Savory coined the term livestock are higher in omega-3 fatty acids
“brittle environment” to denote ecosystems and conjugated lineolic acid than conven-
that receive either low annual precipitation tionally raised counterparts. Additionally,
or experience unpredictable and sporadic these products may reduce cholesterol and
precipitation. (Savory and Butterfield, 1998) reduce the incidence of certain types of can-
These environments are usually character- cer. For more information on the nutritional
ized by shallow soils, limited moisture, and
drought-tolerant perennial grasses, forbs, and
shrubs. Brittle environments respond very
slowly to ecological disturbance. Savory has
suggested that the proper distribution, tim-
ing, and intensity of grazing in these regions
can have a significant and positive effect on
the health of brittle environments. For more
information see the above website or contact
ATTRA at 800-346-9140.
The principal attribute describing grass-
land ecosystems and ruminant nutrition
is interconnectivity. Grasslands and rumi-
nant animals are intrinsically related, and
practices that impact one will necessarily
impact the other. From the soil the system
derives water, nutrients, structural support,
and temperature buffering. Soil popula-
tions of microorganisms recycle nutrients
and make otherwise unavailable nutrients
available for plant uptake. Microorgan-
isms also populate the rumens of grazing Photo courtesy of USDA, NRCS.

www.attra.ncat.org ATTRA Page 3

benefits of grass-based agriculture, visit
The Role of Rumen Microorganisms
Jo Robinson’s website www.eatwild.org.
• Production of cellulase (to break down
Ruminant Physiology fiber-rich plant material)
Proper care of the land and its grazing • Synthesis of volatile fatty acids (used as
animals requires a sound understanding of energy by the animal)
ruminant nutrition. First we must under- • Synthesis of vitamins
stand how a ruminant animal (cattle, sheep,
goats) digests plant matter. • Synthesis of microbial protein

Ruminant comes from the word “rumen,”
which is the fi rst major compartment in cultivation. Cellulose is the portion of the plant
the four-compartment stomach of the cow, structure that comprises the walls of the
sheep, and goat. This structure is the plant’s cells, and is very fibrous and indi-
“furnace” where microbial fermentation gestible. Monogastric (single-stomach, non-
takes place. Millions of bacteria, proto- ruminant) animals do not have the ability to
zoa, and fungi live in the rumen and break digest cellulose. Rumen microbes, however,
down energy-rich plant parts, making produce cellulase, the enzyme that breaks
them digestible for the host animal. After down the chemical bonds in cellulose, mak-
the forage has been digested in the rumen ing it digestible to the microbe and, subse-
and is broken down into small pieces, it quently, to the ruminant animal.
can pass through the reticulum and oma-
Another advantage of rumen fermentation
sum, which function as strainers that keep
is microbial synthesis of important vitamins
large pieces of material from passing into
and amino acids. All the vitamins the ani-
the abomasum, or “true stomach,” where
mal needs are synthesized by microorgan-
digestion continues. From the abomasum
isms, except vitamins A, D, and E. How-
onward, the ruminant digestive system
ever, animals fed high quality hay or green
closely resembles other animal digestive
pasture get their requirement of vitamins A
systems with a small and large intestine,
and E. Vitamin D is supplied through expo-
colon, and anus.
sure to sunlight, which is another advantage
of pasture production. Amino acids are the
Benefits of Ruminant Physiology building blocks of protein—a crucial nutri-
As stated earlier, grazing anima ls ent for growth and reproduction in animals.
have the ability to harvest and convert Rumen microbes synthesize these build-
plant energy, especially cellulose, from ing blocks from ammonia, a by-product of
grasslands and rangelands not suited to fermentation in the rumen. Given this fact,
even poor quality forage can supply some
protein for the grazing animal.
Once it is understood how the rumen works
to convert forage to digestible energy and
protein, it becomes clear how important
grazing animals are to the environment and,
in turn, human culture. Grazing animals
evolved with the prairies and ranges of the
American West, the African steppes, and
Mongolia and have contributed to the devel-
opment of each specific ecological region.
Without the ability to harvest plant energy
from non-farmlands, humans would miss


this crucial contribution to the local and
Critical Components of Feed Quality
world food supply. Grazing animals are the
necessary link between forages and people. Forage nutrient analysis can be a good tool
to determine forage quality. However, forage
Ruminant Digestive Processes quality for grazing animals is more accurately
determined by the following factors, which
“Nutrients absorbed from the digestive tract are affected by observation and adaptive
include volatile fatty acids, amino acids, management of the grazing resource:
fatty acids, glucose, minerals, and vitamins. Related ATTRA
• forage intake
Publications
These are used in the synthesis of the many • forage diversity
different compounds found in meat, milk A Brief Overview
• forage quantity, availability, and density
and wool, and to replace nutrients used of Nutrient Cycling
for maintaining life processes including • appropriate supplementation (energy in Pastures
or protein), when necessary
reproduction.” (Minson, 1990) Digestion Assessing the Pasture
begins when an animal takes a bite from • appropriate minerals—offered free Soil Resource
choice
the pasture. As the animal chews the feed is Cattle Production:
formed into a bolus—a packet of food capa- • and clean, fresh water offered at all times. Considerations for
ble of being swallowed. Saliva is excreted, Pasture-Based Beef
which further aids in swallowing and serves and Dairy Producers
as a pH buffer in the stomach. Once in the The Basics
Dairy Goats:
rumen, the feed begins to undergo fermen- The nutritional concern for ruminants cen- Sustainable Production
tation. Millions of microorganisms ingest ters around energy (i.e., carbohydrates),
Dairy Resource List:
the feed, turning out end products which protein, minerals, vitamins, and water.
Organic and
serve as a major source of nutrients for the Energy (carbohydrates) is responsible for Pasture-Based
animal. Some of the principle products maintenance and growth functions of the
animal, and for the generation of heat. Pro- Dairy Sheep
formed are ammonia, methane, carbon
dioxide, and volatile fatty acids (VFAs). tein grows tissue and performs other vital Goats: Sustainable
VFAs are absorbed and used as energy by functions. Other nutrients and minerals Production Overview

the animal. Ammonia can be absorbed into such as vitamins A and E, calcium, phos- Grass-Based and
the animal’s system through the rumen wall, phorus, and selenium can be fed “free Seasonal Dairying
or can be consumed by bacteria to become choice” as a mineral supplement. The fol-
Managed Grazing in
microbial protein. This microbial protein is lowing section explores the nutrient require- Riparian Areas
then passed through the digestive system to ments of ruminants, beginning with intake.
Meat Goats: Sustain-
be absorbed in the small intestines. Intake able Production

Intake is critically important for acquisi- Sustainable Sheep
Nutrient Requirements of tion of nutrients by ruminants. Intake is the Production
Grazing Livestock ingestion of feedstuffs by the animal, and Pastures: Going
For producers, what are the important is regulated by the following factors, which Organic
nutritional considerations for grazing live- are all interrelated: Pasture, Rangeland,
stock? This is a good question, since live- • palatability and Grazing
stock nutritionists have developed a science Management
• foraging behavior
of nutrient analysis and subsequent ration Pastures: Sustainable
balancing. But the analyses are built on • chemical characteristics of the feed- Management
nutrient content of processed or harvested stuff
feedstuffs delivered to ruminants in pens, • forage quantity, density, and avail-
rather than grazing ruminants selecting a ability
diet from pasture. For this reason, forage • dietary energy and fiber content
nutrient analysis may not be the most reli-
able method to determine feed quality for • physiological stage of the animal
grazing livestock. • and temperature

Palatability is the flavor and texture of the
feedstuff. Ruminants seek sweetness in their Secondary chemicals include “plant
compound[s] capable of producing toxi-
feed, probably because sweet is an indicator
cosis by impairing some aspect of animal
of soluble carbohydrates, the most critical metabolism. Everything is toxic, including
dietary element for the animal after water. oxygen, water, and all nutrients if ingested
Ruminants will in turn avoid feedstuffs that in high enough doses. Most plants, grasses
are bitter, as these often are associated with included, contain toxins. Toxins typically set
toxic secondary chemicals. a limit on the amount of food an animal can
ingest. They do not produce harmful effects
Foraging behavior describes how an animal if ingested in limited amounts. Under cer-
goes about the grazing process. According tain circumstances, animals have difficulty
to Fred Provenza, range researcher at Utah refraining from overingesting certain plants
State University, the study of animal graz- that contain toxins—the so-called poisonous
plants.” (Provenza, 2003)
ing behavior involves understanding:
• food habits and habitat preferences,
and associated with plant defense. Secondary

A
• the effects of nutrients and toxins on chemicals are often referred to as toxic sub-
nimals stances, but toxicity is really just a matter of
preference
limit the degree, of dosage. All plants contain toxic
“Our work has shown,” he writes, “how sim-
amount
ple strategies that use knowledge of behav- secondary chemicals to some degree, but
of plants they con- ior can markedly improve the efficiency and animals have evolved an innate sense of
sume that contain profitability of agriculture, the quality of life what is good to eat.
secondary chemicals for managers and their animals, and the Animals limit the amount of plants they
through a feedback integrity of the environment.” (Provenza, consume that contain secondary chemicals
2003) For instance, grazing livestock, unlike
mechanism that through a feedback mechanism that results
closely confined livestock, have the opportu-
results in satiety, or in satiety, or the feeling that they have had
nity to graze selectively, and therefore tend
the feeling that they to select a diet higher in leaf content than enough. According to Webster, satiety is the
have had enough. what the overall pasture has to offer. (Min- “quality or state of being fed or gratified to
son, 1990) For more information on grazing or beyond capacity, or the revulsion or dis-
animal behavior see www.behave.net and gust caused by overindulgence or excess.”
www.livestockforlandscapes.com. When ruminants consume enough of a cer-
tain toxic substance, a feedback mechanism
Bite size and bite rate also have an influ-
induces a switch to an alternative source of
ence on intake. The more dense a pasture
sward, the more forage the animal can take nutrients. This is why cattle, sheep, and
in with each bite. Research has shown that goats graze more (have higher intake) on
a dense, vegetative pasture yielding at least a diverse pasture. The variety stimulates
2,000 pounds of dry matter per acre is ade- their appetite and provides alternative
quate for maximizing bite size, and there- sources when they reach the limit of their
fore intake. However, when pasture yield fi rst choice of plants.
drops below 2,000 pounds of dry matter
per acre, intake decreases. (Minson, 1990)
Secondary Chemicals in Forages
This exemplifies the fact that the relation-
ship between grazing management, animal • Alkaloids in reed canarygrass and
behavior, and nutrient uptake is not a sim- lupines
ple relation. It is complex and constantly
• Tannins in trefoil and lespedeza
changing, following the changes of the sea-
sons, forage quality, and forage quantity. • Terpenes in sagebrush and bitterweed
Chemical factors include nutrients, but • Endophyte toxin in tall fescue
also secondary chemicals that are often

Forage quantity, density, and availability ruminants are soluble carbohydrates. What
directly influence forage intake, and intake an animal actually eats from a pasture is
is directly related to the density of the often of higher nutritional quality than the
pasture sward. Ruminants can take only a average of the pasture overall. Forages with
limited number of bites per minute while a dry matter digestibility (DMD) of 60 to 69
grazing, and cattle in particular will only percent are considered high quality forages
graze for about 8 hours per day. It is impor- from an energy perspective. Dietary fiber is
tant then to ensure that each bite taken by also a forage quality indicator.
the grazing animal is the largest bite she
Fiber is necessary for proper rumen function,
can get. A cow grazes by wrapping her and is a source of energy as well. However,
tongue around and ripping up forage; sheep high levels of fi ber in the diet decrease
and goats use their lips and teeth to select intake. Less digestible forages tend to stay
highly nutritious plant parts. Large bites of in the animal’s digestive system longer
forage are therefore ensured by maintaining (slowing the rate of passage) so the animal
dense pastures. remains “full” longer, and subsequently
Dense pastures are those with actively doesn’t eat as much. However, the younger

R
growing and tillering forage plants. Til- a plant is the more soluble carbohydrates it uminants
lering occurs in grasses that are grazed or contains, and the less fiber (cell wall com-
possess
mowed while vegetative, resulting in the ponents) it contains as well. Younger plants
therefore are generally more digestible than nutritional
activation of basal growing points (clusters
of cells that initiate growth near the bottom mature plants. wisdom and will
of the plant) and the growth of new stems Physiological stage refers to the stage of life
select diets high in
and leaves. Tillering results in a plant cov- the animal is in, and what level and type digestible organic
ering more basal area, which helps make a of production are being supported. The key matter, because the
pasture denser, while protecting the soil. physiological stages in the life of ruminant most critical nutri-
The length of the grazing period (the time animals are: ents selected by
an animal is in a paddock) also has a • growth (i.e., young lambs, kids, and ruminants are solu-
direct effect on pasture intake. An animal’s calves, including feeder animals) ble carbohydrates.
intake decreases the longer she remains in
a given paddock. This happens due to (1) • late pregnancy (very important in
the effect of plant disappearance (as plants sheep and goats)
are grazed) and subsequent searching by • lactation (for dairy production or
cattle for the next bite, and (2) the decrease maintenance of offspring)
in forage crude protein content begin- • and maintenance (such as the cow’s
ning roughly two days after the animals dry period)
have been turned in to the paddock. Jim
Gerrish has shown that as an animal For example, the peak intake of dairy cattle
remains in a paddock, intake and liveweight occurs after peak lactation. Between peak
lactation and peak intake, the body must
gains decrease. (Gerrish, 2004) It is for
draw on stores to maintain energy balance.
this reason that most dairy graziers move
Thus dairy animals generally lose body
high-producing cattle to new paddocks after
condition during this period. For this rea-
each milking.
son it is important to ensure high-quality
Dietary energy and fiber content. As has pasture to maintain productivity and opti-
been mentioned, livestock eat to the point of mum health, as well as to ensure the ani-
satiety. Another good definition of satiety is mal’s ability to rebreed and enter into lac-
gastrointestinal satisfaction. Ruminants pos- tation at the appropriate time the following
sess nutritional wisdom and will select diets season. On the other hand, a dry ewe can
high in digestible organic matter, because gain weight on “fresh air and sunshine”—
the most critical nutrients selected by maintenance requirements are low, and this


is the perfect time to let the sheep clean up Energy intake maintains body functions and
over-mature forage, with no harm done. facilitates growth and development, includ-
ing reproduction and lactation. Energy is
Temperature affects the amount of feed an
supplied to ruminants by highly digestible
animal needs to maintain its body func-
plant cell contents and a portion of the less
tions. An animal’s metabolic rate increases
digestible plant cell wall fraction. Starches
as the temperature drops below the ani-
like corn and barley are also high energy
mal’s comfort zone. As temperature drops,
sources, and are used extensively in the
more energy is needed to maintain internal
conventional livestock feeding industry as
heat, so intake increases accordingly. Sub-
sequently, animals typically will not graze well as for pasture-based systems where
as much during hot, humid weather. energy supplementation is sometimes use-
ful to enhance production.
Options for Increasing Intake on Not all the energy taken in by a grazing
High Quality Pasture animal becomes meat, milk, or wool. The
hierarchy of energy digestion begins with
High intake is one of the simplest meth- gross energy, which is the energy of intake.
ods of ensuring adequate nutrition for high Some of the energy of intake is digestible,
Intake is producing ruminants. Ensure high forage
maximized when and some is not. What is not digestible is
pastures are:
intake by: excreted as fecal energy, and what is left
• keeping forage in the vegetative for use by the body is digestible energy.
• dense
stage through grazing management, Metabolizable energy is the energy left after
• digestible
accounting for digestive and metabolism
• palatable • diversifying pasture composition to
losses. Some of the digestible energy is lost
• diverse include several grass species, with
as urine, and some as methane. What is left
around 30 percent of the pasture in
• correctly stocked
legumes, and is energy used for the maintenance of body
• plentiful (8-10” temperature, respiration, growth, reproduc-
tall for cattle, 6- • maintaining a dense pasture so tion, and milk production. This fraction is
8” for sheep) animals will take larger bites. called net energy and is usually split into
• familiar to the
net energy for maintenance (NEm), net
animal Energy energy for gain (NEg), and net energy for
• fresh (not tram-
pled or heavily Energy is the single most important dietary lactation (NEl). Animals can adjust to avail-
manured) component for an animal after water. Energy able energy by putting on fat or by using
is derived from carbohydrates, fats, pro- fat stores. For more information see the box
teins, and from the animal’s body reserves. entitled “Body Condition Scoring.”

Good, plentiful pastures assure healthy, productive animals. Animals are not productive when pastures are inadequate.
Photo courtesy of USDA, NRCS. Photo courtesy of USDA, NRCS.


Body Condition Scoring Energy Partitioning. From USDA, 2003.

Body condition scoring is a method of visu-
ally appraising animals to arrive at a quali-
tative description of nutritional status.
Animals must not be too thin or too fat or
complications can arise. If too thin, animals
may not conceive, may be prone to disease,
and usually have reduced milk production.
If too fat, animals may experience difficulty
giving birth (dystocia).
Body condition scores are ranked on a
numerical scale. The lower the number on
the scale, the thinner the animal. For sheep
and dairy cattle, the scale is from 1 to 5. For
beef cattle, the scale is 1 to 9.
Optimum BCS for Breeding Livestock
Sheep ......................... 3.0 to 4.0
Dairy Cattle .............. 2.5 to 3.0
Beef Cattle ............... 4.5 to 5.0
The Resources section of this paper lists sev-
When protein is degraded in the rumen it
eral publications addressing body condition
scores for various species. The publications
is called rumen degradable protein. Rumen
include charts to assist producers in making degradable protein is essentially food for
visual appraisals of livestock and assigning rumen bacteria. When the microbes die
the appropriate body condition score. they are passed through to the stomach and
small intestines where they are digested by
the animal. The resulting microbial protein
is then absorbed into the animal’s blood-
Protein stream. Some of the protein in the diet does
“Crude Protein (CP) is calculated from not undergo degradation in the rumen, but
the nitrogen content of the forage. The CP passes straight to the abomasum or stomach
value is important since protein contrib- for digestion. When protein escapes rumen
utes energy, and provides essential amino breakdown and passes to the stomach it is
acids for rumen microbes as well as the referred to as rumen undegradable protein
animal itself. The more protein that comes or bypass protein.
from forage, the less supplement is needed.
However, most nutritionists consider energy
value and intake of forages to be more
important than CP.” (Robinson et al, 1998) Protein Flow.
As has been discussed, the energy value of
a forage is best determined by forage matu-
rity, density, and availability. Protein in for-
ages is most correlated with forage matu-
rity, as more mature forages have a lower
percentage of crude protein.
Cattle require two types of protein in their
diet. One type is degraded in the rumen
and is used to meet the needs of the micro-
bial population, and the other bypasses the
rumen and is used primarily to meet the
productive needs of the animal.

Bypass protein is important because a large important, especially for high-producing
percentage of the rumen degraded protein livestock such as dairy animals, even in
is absorbed as ammonia and, if in high con- protein-rich-pasture diets.
centrations, can be lost through the urine as
Some animal nutritionists suggest that
urea. In high-producing animals this rep-
bypass protein has been overemphasized.
resents an inefficient utilization of protein,
This is because the total proportion of
so increasing the amount of protein that is
bypass protein in most forages is around 30
bypassed to the intestines constitutes a more
percent, which is very close to the require-
efficient utilization of protein for growing or
ments of the ruminant animal. In this case,
lactating animals on high-quality pastures.
they suggest, feeding the rumen microor-
In forages, roughly 20 to 30 percent of the
ganisms takes on particular importance, for
protein taken in by the animal is bypassed
if the rumen microorganisms are healthy,
to the intestines. Lactating or growing
they will supply the ruminant with the nutri-
cattle generally require 32 to 38 percent of
ents they need to maintain body functions
their total protein intake to be in the unde-
and remain productive. We must remember
gradable form. (Muller, 1996) High-quality
that ruminant animals evolved in symbio-

V
pastures can meet almost all the needs of
itamins are sis with rumen microorganisms in a grass-
high-producing livestock. For those animals
land environment, and they are inherently
important that require supplementation, corn, cot-
adapted to this function.
for the for- tonseed and linseed meals, brewers dried
mation of catalysts grains, corn gluten meal, distillers dried
grains, and fish meal are typically high in Minerals and Vitamins
and enzymes that
bypass protein. The principle minerals of concern for live-
support growth and stock on growing forages are calcium and
body maintenance The microbial degradation of protein is an
magnesium. Others to consider are salt,
energy-dependant process. Carbohydrates
in animals. phosphorus, potassium, and sulfur. These
are the energy-yielding nutrients in animal
minerals are very important for cellular res-
nutrition and are supplied by the produc-
piration, nervous system development, pro-
tion of volatile fatty acids in the rumen.
tein synthesis and metabolism, and repro-
Generally more microbial protein is synthe-
duction. Mineral supplements are available
sized from green forage diets than from hay
in many formulations. Because soils differ
or mature forage diets. When a ruminant
in mineral content from place to place, it is
animal grazes fresh forage on high-quality
difficult to recommend a mineral mix that
pasture, about 70 percent of the protein is
works in all places, although most animal
degraded in the rumen by microorganisms,
scientists suggest at the very least a min-
and about 30 percent escapes to the small
eral mix with a calcium to phosphorus ratio
intestine for absorption. Ruminant animals
of 2:1. Consider using a loose mineral mix
need approximately 65 to 68 percent of the
fed free choice rather than mineral blocks
protein to be rumen degradable for ade-
for cattle on lush spring or small grain pas-
quate rumen function and the development
ture to avoid grass tetany (hypomagnese-
of microbial protein. But if more protein is
mia) and to ensure the animals are getting
degraded in the rumen, less is available to
enough mineral.
the animal for absorption in the small intes-
tine. This is important because researchers Vitamins are important for the formation of
believe that rumen undegradable or bypass catalysts and enzymes that support growth
protein consists of certain essential amino and body maintenance in animals. Green
acids that are missing or deficient in rumen growing plants contain carotene, which is a
degradable protein. Much of the rumen precursor to vitamin A. If ruminants are on
degraded protein is absorbed as ammonia green forage (including green hay) vitamin
and excreted out of the body via the urine, A should not be deficient. Vitamin A defi-
and is therefore a waste of protein. This ciencies occur when ruminants are placed
is why bypass or undegradable protein is on concentrate feeds, or when fed dry,

stored forage during the winter. B vitamins
are synthesized by rumen microorganisms
so supplementation is not necessary. Vita-
min D is synthesized in the skin from expo-
sure to sunlight, so Vitamin E is the only
other vitamin of concern that sometimes
requires supplementation.
Mineral and vitamin supplementation is
very important to maintain herd health, and
careful attention must be paid in develop-
ing a mineral and vitamin supplementation
plan. Keep these things in mind when feed-
ing these supplements to livestock:
1. Keep mineral mixes dry. Wet mineral is
unpalatable and is known to lose some of
its efficacy when damp.
2. Monitor consumption to make sure it’s Photo courtesy of USDA, NRCS.
always available. Keep the feeders full.
3. Don’t forget that some animals display toxic chemicals. Examples are knapweed,
social dominance. Older, more dominant sagebrush, and scotchbroom.
animals will often eat more than their
Cattle require from 3 to 30 gallons of water
share of mineral mix. Remedy this by
having more than one feeder, separated per day. Factors that affect water intake
into different parts of the pasture. include age, physiological status, tempera-
ture, and body size. A rule of thumb is that
cattle will consume about one gallon of water
Sheep and Copper Toxicity per 100 pounds of body weight during win-
ter and two gallons per 100 pounds of body
Sheep are very sensitive to copper. If you have weight during hot weather. In general, you
cattle and/or goats, and sheep on the same can easily double the estimates for lactating
farm it is extremely important to supply them cattle. Water should be clean and fresh, as
with different mineral mixes, as a mix that is for-
mulated for cattle or goats will likely be lethal
dirty water decreases water intake. It is good
for sheep. Loose mineral mixes are better than to remember that all other nutrient metabo-
blocks for sheep and goats. lism in the body is predicated on the avail-
ability of water, and if an animal stops drink-
ing, nutrient metabolism (which results in
growth and lactation) will decrease.
Check with your local Extension agent or
veterinarian to determine the mineral and
vitamin mixes and recommendations com- Forage Resources and
mon to your area. Grazing Nutrition
Nutrient content of forages varies with plant
Water maturity. As the plant matures, it shunts
Sheep and goats require one gallon of water sugars and proteins to the reproductive
per day for dry ewes, 1.5 gallons per day centers of the plant, namely the seed (in
for lactating ewes, and 0.5 gallons per day the case of annuals) and the roots (in the
for finishing lambs. Water consumption will case of perennials). Plant maturity results
increase during the heat of the summer, and in more fibrous, and less digestible, leaves
when the animals are grazing or browsing and stems. Various circumstances affect
plants with high concentrations of secondary, plant maturity. Among the most common


factors contributing to plant maturity and relatively high TDN levels and protein com-
subsequent forage quality are: positions of 5 percent. (Ricketts, 2002)
Shrubs tend to have their highest nutrient
• length of growing season (plants
content in the spring as well, but generally
mature faster in shorter growing
retain a higher nutrient content throughout
seasons)
the growing season and into the dormant
• moisture availability (moisture period. Most shrubs, such as greasewood
stress reduces photosynthetic activ- and saltbush carry a protein content of
ity and initiates dormancy) greater than 12 percent in the winter. Forbs
• pasture plant species composition are high in protein as well. Purple prairie
(some species remain vegetative lon- clover and dotted gayfeather have as much
ger than others) or more protein, when green, than alfalfa
• and the grazing system and clover. “These forbs are like little pro-
tein blocks scattered on the landscape.”
Of these factors, the one that livestock manag- (Ricketts, 2002)
ers have the most control over is the grazing
system. Controlled defoliation and adequate Grasses. Grasses are divided into two types:
rest are crucial for plants to remain vegeta- warm season and cool season. On semi-arid
tive, and therefore more nutritious, during prairies and western ranges, warm season
the growing season. This topic is summa- grasses do most of their growing from May
rized in the Grazing Management section to August, whereas cool season grasses do
of this publication and covered in detail in their growing from March to June. Knowl-
the ATTRA publications Pasture, Rangeland, edge of which grasses are in your pastures
and Grazing Management, Rotational Grazing, will help you to decide when to graze them
and Pastures: Sustainable Management. to take advantage of highest nutrient con-
tent. In the spring, grasses will have a pro-
Plant Type, Species, and Nutri- tein content of approaching 20 percent and
will be around 10 percent protein when in
tional Quality on Native Range mid-bloom, or when half the plants have
There are three basic plant types commonly developed a seedhead.
found in pastures, and each has its place in
animal nutrition. These plant types are: On deteriorated dry western range sites, you
might see a proliferation of Kentucky blue-
• Grasses grass, bottlebrush squirreltail, and cheat-
• Shrubs grass. The weedy grasses can be good in
• Forbs nutrient value, but generally do not produce
enough annual forage to meet the needs
Grasses tend to be high in nutrients in the of grazing livestock, and are often vegeta-
spring, and begin to decline as the grow- tive for a very short period of time, as with
ing season progresses. By the time winter cheatgrass and squirreltail. Broadleaf weeds
sets in, rangeland grasses such as rough become coarse and unpalatable very soon
fescue and bluebunch wheatgrass will have after they begin to mature. Pastures that have
greater than about 50 percent of these plants
Feeding Value of Forages should be considered for a serious revision of
Crude Protein % the grazing system, or pasture renovation if
TDN %
Grass Legume appropriate. Consider multi-species grazing,
because sheep and goats may eat the weeds
Vegetative 63 15 21 that cattle do not, thus bringing the pasture
Boot or bud 57 11 16 back in balance.
Bloom 50 7 11 Shrubs. Shrubs are very good to have on
Mature 44 4 7 native range because they are high in pro-
Adapted from Fisher, 1980 tein for a greater part of the year. Many


livestock and wildlife find these plants
A Case for Species Diversity
important for getting them through the win-
ter. Shrubs on many western ranges include As shrubs and forbs typically have higher protein concentrations than
winterfat, sagebrush, fringed sagewort, four- most grasses, why are they generally considered substandard as live-
wing saltbush, snowberry, and rabbitbrush. stock forage? The main reason is that most shrubs and many forbs con-
These plants will generally have more than tain secondary chemicals that are often toxic to grazing animals. Animals
seven percent protein content through the grazing sagebrush, for example, will very quickly get their ﬁll as the level
winter. Combined with other dormant for- of alkaloids accumulates in their systems However, livestock display
ages, these plants can often supply an ani- nutritional wisdom and often eat small portions of various species in
order to (1) obtain essential nutrients, and (2) neutralize the eﬀects of
mal with its maintenance needs for protein more toxic plant species.
if there are enough plants.
Cattle are typical grazers, and utilize grass
as their primary food source. They will, Berseem clover are often overseeded into
much like goats and sheep, browse on win- warm season pastures with annual ryegrass or
terfat and saltbush. A range site with 20 to small grains in the humid South to supply high
30% of its cover in a diverse population of quality winter pasture to cattle from October
shrubs serves to sustain all classes and spe- through April. Some excellent warm season
cies of livestock as well as provide winter
legumes to consider in temperate regions are
food and cover for wildlife.
annual cowpeas and perennial peanuts. Tur-
Forbs. Forbs, or non-woody broadleaf nips also make an excellent season extension
plants, are generally higher in protein than annual crop for providing high-quality graz-
grasses. Many forbs are considered weeds, ing into the fall in some temperate regions.
but most are often palatable and nutritious For more information on alternative forages
when immature. Typical rangeland forbs to extend the grazing season, see the ATTRA
that are high in protein and digestibility publication Pasture, Rangeland, and Grazing
include gayfeather, western yarrow, prairie Management at www.attra.ncat.org or call the
clover, and Indian paintbrush. On dryland ATTRA help line at 1-800-346-9140.
ranges, high-dormancy alfalfa can make a
very good supplement for livestock, as do Matching Nutritional
birdsfoot trefoil and cicer milkvetch, which
in addition to being high-quality forage, Requirements of Livestock to
have anti-bloat characteristics as well. the Forage Resource
One of the most important questions a live-
Plant Type and Species on stock manager can ask is “what do I need
Temperate Pasture to know in order to match the nutritional
requirements of my animals to the forage
Grasses and forbs generally dominate shrubs
resource?” To answer this question with
in temperate regions. On temperate pastures,
the highest level of certainty, the producer
warm season grasses exhibit growth from as
should perform the following crucial man-
early as March to as late as September, and
cool season grasses grow well from October agement tasks:
into June, with reduced growth during the • inventory available forage resources
winter months. Indicators of poor pasture (documenting re-growth, crop resi-
condition on temperate pastures are grasses due, etc.)
such as sandbur, rattail smutgrass, and little
• prioritize grazing of highest qual-
barley, and broadleaf weeds like curly dock,
ity pastures by animals with high-
croton, and hemp sesbania.
est nutrient requirements (growing,
The most common forbs used on temperate lactating)
pastures include clovers, alfalfa, and vetches. • observe and determine the forage
White clover, hairy vetch, red clover, or growth curve for your pastures

• coincide the forage growth curve (birth) and lowest demand is three to four
with peak animal demand months before parturition. (Gerrish, 2004)
• monitor to ensure animal numbers For sheep, just before lambing to weaning
and type are appropriate to forage are crucial times when nutrient require-
resource ments are highest, especially just prior to
lambing. For dairy animals, the entire lac-
Forage Growth Phases tation period is critical. Knowing the forage
growth curve for your pastures will allow
Forage supply is not continuous through- you to match forage growth with animal
out the year. You can expect anywhere demand. For example, consider having ewes
from three to nine months of growing sea-
lamb when grass is at optimum productivity
son, and three to nine months of dormancy,
and when the ewes need it the most. On the
depending on the region. Cool-season pas-
other hand, think about the needs of young
ture growth begins in the early spring and
stock. Unless you are selling at weaning,
quickly produces very large amounts of for-
you need a plan for high-quality pasture for
age, then tapers off toward mid-summer.
young growing animals.
Given adequate moisture, cool-season pas-
tures will often produce a second surge of
growth in the fall before going dormant. Supplementing Protein or
Warm–season pasture begins later in the Energy: When is it Necessary?
spring and continues into early autumn Cattle, sheep, and goats, by nature grazing
when day length shortens and tempera- and browsing animals, grow and reproduce
tures fall. Warm-season pastures comple- well on pasture alone. However, an inten-
ment cool-season pastures nicely by provid- sive and industrial agricultural production
ing forage when cool-season growth wanes philosophy has dictated that crops and ani-
in mid-summer. A diverse mix of cool- and mals should be raised faster, larger, and
warm-season pastures benefits livestock more consistently than a pasture system
managers by overlapping the growth curves can deliver. Thus confinement systems with
of both types, meaning more high-quality delivered forages and concentrated feeds
pasture than otherwise. have been the norm since the 1950s. Rais-
ing animals on grass is slower than raising
Peak Animal Demand animals on grain. However, a pasture-based
The highest nutrient demand for beef cat- livestock producer will, with careful plan-
tle is one to three months after parturition ning, realize cost savings and subsequent
profitability through the efficiency of relying
on the natural systems of nutrient cycling,
biological pest controls, and perennial
pasture productivity.
The major operational expense confronting
the livestock industry in most parts of the
United States is for supplemental feed. In
temperate regions of the country that experi-
ence adequate rainfall and a lengthy grazing
season, supplementation on green, growing,
vegetative, well-managed pastures should not
be necessary. However, young and lactating
stock require more energy and protein than
mature, non-lactating animals.

District Conservationist Rhonda Foster and Grasslands management Specialist
Well-managed grass-legume pastures
Ralph Harris disucss intensive grazing rotations at a farm in Benton County, Georgia. can be highly digestible with protein con-
The producer grazes his cattle on a 3 week rotation. Photo courtesy of USDA, NRCS. centrations approaching 25 percent while

vegetative. These pastures can supply the Remember:
nutrients needed to raise lambs, kids, heif-
• Substitution effect—forage intake
ers, or steers, or support lactating cattle,
decreases with less fi brous, more
sheep, or goats. The problem on high-qual-
digestible supplements like corn.
ity pastures often becomes one of ineffi-
cient protein use. Supplementing energy • Supplementation of protein on low-
with digestible fi ber in these situations can quality forages will increase for-
make the animals utilize protein more effi- age intake, and therefore increase
ciently. Digestible fi ber (energy) sources energy intake.
include wheat middling (a coproduct of
wheat processing sometimes called midds), Concept of First Limiting Nutrient
soybean hulls, corn gluten feed, and whole Determine which nutrient is limiting and supplement that one first.
cottonseed. (Jackson, undated) For instance, degradable intake protein requirements need to be met
for microbial growth first. Then and only then consider bypass protein
Corn is grown on many small diversified supplementation, and only if it is deficient. Likewise, if energy is defi-
farms, in rotation with pasture, legumes, or cient, protein supplementation will be wasteful and expensive.
vegetables, as animal feed, and is an excel-
lent source of low-fi ber energy for graz-
ing ruminants. However, if corn is fed in Remember: on high-quality pastures,
high quantities, forage intake will decline. energy is often the limiting nutrient. Digest-
A pound or two a day for sheep and goats ible fiber feeds are good for ruminants on
and five or six pounds per day for cattle high quality forage because they do not
will generally provide enough supplemen- reduce intake, and provide energy for pro-
tal energy without decreasing forage intake. tein metabolism. Examples are: corn gluten
Limiting corn supplementation to no more feed (corn gluten meal plus the bran), wheat
than 0.5 to 1.0 percent of body weight per midds (screenings from wheat flour process-
day is recommended for cattle on pasture. ing), and whole cottonseed.
(Sewell, 1993)
Feeding Cottonseed Products to Cattle
When to Supplement Three types of cottonseed products are typically fed to beef and dairy
cattle. These are whole cottonseed with lint, cottonseed meal, and cot-
• Supplementing energy is helpful on veg- tonseed hulls. Whole cottonseed is a very good source of protein for
etative, well-managed pastures for more cattle. However, whole cottonseed contains a chemical called gossypol
efficient utilization of forage protein (for that can inhibit the reproductive performance of breeding cattle, par-
high producing animals). ticularly bulls. For this reason it is recommended that producers limit
• Supplementing with protein is necessary whole cottonseed supplementation to calves at 1.5 pounds per day,
on low-quality pasture and rangeland or stocker cattle at no more than 3 pounds per day, and mature cows at 5
when continuously grazing temperate pounds per day. Avoid feeding whole cottonseed to bulls.
warm-season pastures.

Forage Sampling and
When supplementing ruminants on pasture, Production (Yield) Estimates
consider the following questions:
If you choose to have your forage analyzed
• Will the added production cover the for nutrient content, the key nutrients to
expense, especially if the feed is consider are crude protein (CP) and total
shipped from off the farm? digestible nutrients (TDN). Acid detergent
• Is there an inexpensive local source fiber (ADF) and neutral detergent fiber
of protein? (NDF) are useful as well for determining
energy content. ADF and NDF measure
• Do you raise the feed on the farm? fiber, or cell wall contents. The higher the
• Do you have necessary harvest, fi ber the lower the energy value is for a
storage, and feeding equipment? feedstuff.


Although determined by a system that relies
Your Local Cooperative
on harvested forages, these two measures Extension Office
will give the producer a good starting point
to make decisions about supplementation. Contact your local Cooperative Extension
For cattle, forage with 10 to 13 percent CP office for information on poisonous plants,
and 55 to 60 percent TDN will meet all the forage analysis, and locally adapted forages.
needs of most classes of livestock. Growing The USDA maintains an online database of
and lactating livestock need added protein local Cooperative Extension offices on its
and energy if the forage resource is not of website at www.csrees.usda.gov/Extension/
index.html. You will also find the phone num-
adequate quality. Also important is mineral ber for your Cooperative Extension office in
content. Different soils in different areas the county government section of your tele-
of the country can be deficient in different phone directory.
nutrients. Selenium and copper availability
are a problem in the southeast and north-
west, for instance. Check with your Coop-
erative Extension office or state Extension Grazing Management
forage or beef specialist to determine the Grazing management is the regulation of

G
razing mineral needs in your area. the grazing process by humans through
manage- Estimating forage yield in a pasture also the manipulation of animals to meet
ment is the plays a very important role in developing a speci f ic, predetermined product ion
regulation of the nutrition plan for grazing livestock. There goals. (Briske and Heitschmidt, 1991)
are many ways to estimate forage yield, from The primary considerations of grazing
grazing process by
the more time-consuming clip-and-weigh management are:
humans through
approach to more generalized estimates • temporal distribution of livestock
the manipulation of from plant height and density. The ATTRA (time)
animals to meet spe- publication Pasture, Rangeland, and Grazing • spatial distribution of livestock
cific, predetermined Management includes formulas and instruc-
production goals. tions for estimating forage yield and develop- • kind and class of livestock
ing an appropriate stocking rate. • a nd number of l ivestock
(Heitschmidt and Taylor, 1991)
Plant Toxicity and Grazing- If given a choice, livestock will only eat the
Related Disorders highest quality, most palatable plants in a
Graziers must pay careful attention to the pasture. In order to ensure that plant bio-
negative health effects that certain plants diversity is maintained in the pasture it is
can cause in livestock. Plant toxicosis occurs necessary to set up a grazing management
either through the ingestion of (1) poisonous system to better control livestock grazing.
plants or (2) forage plants that contain toxic The elements of grazing to control are tim-
substances due to environmental or physi- ing and intensity of grazing. This means
ological conditions. Plant poisoning can controlling the number of animals and how
be significantly reduced by proper grazing long they are in a pasture.
management. Poisonous plants contain res- Rotational grazing systems take full advan-
ins, alkaloids, and/or organic acids that ren- tage of the benefits of nutrient cycling as
der them unpalatable. If the pasture contains well as the ecological balance that comes
enough good forage, there is little reason for from the relationships between pastures
the animals to select bad-tasting plants. The and grazing animals. High density stocking
ATTRA publication Pasture, Rangeland, and for short periods helps to build soil organic
Grazing Management contains detailed infor- matter and develops highly productive,
mation on plant toxicity and grazing-related
dense, resilient pastures.
disorders. In addition, your local Cooper-
ative Extension office has information on Some other measurements to consider in
poisonous plants in your area. managing livestock grazing include:

• forage density
• after-grazing plant residue
• paddock rest time
• range condition and trend,
• animal body condition, health, and
physiological stage
• grazing systems, including stocking
rate and stock density
• and pasture and rangeland monitoring
These considerations are covered exten-
sively in other ATTRA publications. For
more information on grazing management
see the ATTRA publications Pasture, Range-
land, and Grazing Management; Rotational
Grazing; and Paddock Design, Fencing, and
Water Systems for Controlled Grazing. Photo courtesy of USDA, NRCS.

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Notes


Ruminant Nutrition for Graziers
By Lee Rinehart
NCAT Agriculture Specialist
©2008 NCAT
Paul Driscoll, Editor
Amy Smith, Production
This publication is available on the Web at:
www.attra.ncat.org/attra-pub/ruminant.html
or
www.attra.ncat.org/attra-pub/PDF/ruminant.pdf
IP318
Slot 52
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