NUTRITION PIH-3
PURDUE UNIVERSITY. COOPERATIVE EXTENSION SERVICE.
WEST LAFAYETTE, INDIANA
Dietary Energy for Swine
Authors
Palmer J. Holden, Iowa State University
Gerald C. Shurson, University of Minnesota
James E. Pettigrew, University of Minnesota
Reviewers
Richard C. Ewan, Iowa State University
John P. Hitchcock, University of Tennessee
William G. Luce, Oklahoma State University
Pigs require energy to maintain normal body processes, to
grow and to reproduce. Feeds supplying energy are major com-
ponents of all swine diets, and the quantity of diet voluntarily
consumed by pigs is related to its energy content. Carbohydrates
from cereal grains are the most abundant energy source in swine
diets. Fats and oils contain more energy than carbohydrates per
unit weight but are included to a lesser extent. Amino acids, or
protein, may serve as an energy source if included in the diets
in excess of animals' requirement for protein synthesis.
The value of a feedstuff is based on several factors: pala-
tability (how well the material will be consumed by an animal),
availability of energy and the feed's contribution of other
nutrients (protein or amino acids, vitamins, minerals). Should a
pork producer buy corn, wheat, or oats as a feed ingredient? This
depends primarily on the cost of these ingredients and their
value as sources of energy and other nutrients for the pig.
Measurement of Energy
To make sound decisions in selecting feed ingredients, it is
desirable to have an understanding of the system by which
feedstuffs are rated for energy content and the use of these rat-
ings toward meeting the energy requirements for pigs' growth and
production. The gross energy (GE) of a feed ingredient is defined
as the heat produced when a substance is burned. It is expressed
as calories per unit weight. A calorie is the amount of heat
required to raise the temperature of one gram of water from 14.5
to 15.5 degrees C. A kilocalorie (kcal) is 1,000 calories, and a
megacalorie (mcal) is a million calories.
Not all of the feed consumed is digested and absorbed. Some
energy is lost in the fecal material (Fig. 1). Thus, GE is a poor
estimate of energy for the pig. The amount of energy remaining
after subtracting the fecal energy loss from total energy intake
is designated as digestible energy (DE). The difference between
GE and DE may be large. The greater the digestibility of energy
(DE/GE) the greater its value as a source of energy to the
animal. DE is a more meaningful measure for livestock producers
than GE.
Metabolizable energy (ME) is the "usable" energy of a feed
for the pig to live and grow and is obtained by subtracting the
urinary energy loss from the DE. In most cases, metabolizable
energy represents approximately 95% of the digestible energy con-
tent, so the conversion from DE to ME can be made easily.
Some energy is released as heat as a result of inefficien-
cies in the metabolism of the nutrients. This is called the heat
increment (HI). It can be used only to keep the animal warm; heat
increment produced beyond that needed to maintain body tempera-
ture is wasted. The remaining energy is called net energy (NE)
and is used for maintenance (NEm) and production (NEp). Determi-
nation of NE values requires special equipment and/or animal
feeding trials.
Major Energy Sources
Cereal Grains
The basic energy sources for swine are the cereal grains:
corn, sorghum grain (milo), barley, wheat, oats and their by-
products. Cereal grains are high in carbohydrates (starch),
palatable and highly digestible. Usually they contain less lysine
and other amino acids, minerals and vitamins than swine require.
The diets therefore must be supplemented with other feeds to
increase these nutrients to recommended levels.
Grain by-products have many characteristics of their origi-
nal source but tend to be bulkier and have less metabolizable
energy. Although their protein content usually is increased, the
protein quality often is rather poor.
Corn contains less protein but more energy than the other
cereals. Like all cereals, the composition of corn is influenced
by variety, growth conditions, method of harvesting and storage.
Because of its abundance and readily available energy, corn is
used as the base grain for comparing the nutritive value of other
cereal grains. Grinding is recommended except for high moisture
corn.
Sorghum grain is similar in quality to corn and can com-
pletely replace corn in swine diets. Its energy value is about
95% of the value of corn except for some bird-resistant varieties
which may be only 80% to 90% of the value of corn. Grinding is
recommended because the grain is rather small and hard.
Barley contains more protein and fiber than corn. High qual-
ity barley has 90% to 100% of the feeding value of corn, but it
may be less palatable.
Wheat is equal to corn in feeding value and is very palat-
able when it is medium to coarsely ground in complete rations.
Wheat can completely replace corn in swine diets.
Oats contain more protein than corn, but their value in
swine diets is only 90% of corn because of their higher fiber and
lower energy content.
Fats and Oils
Fats and oils contain about 2.25 times as much metabolizable
energy per pound as cereal grains, but they are more expensive.
Fats are available commercially in products such as bleachable
fancy tallow, prime tallow, yellow grease, hydrogenated vegetable
fat and various dry fat products which include fat and a dry car-
rier. Fat sources should be protected from rancidity by an
antioxidant. There do not appear to be major differences in
dietary value among the fat sources, except for very young pigs
which may not utilize the harder animal fats as well as softer
vegetable fats. Vegetable oils and the dry fat products tend to
be more expensive than animal fats.
Supplemental fat is difficult to mix in on-farm mixing
facilities, especially in cold weather. Fat changes the physical
characteristics of a swine feed. Feed containing added fat is
somewhat sticky and therefore tends to bridge in bulk bins and
feeders. It tends to "oil out" of paper bags and reduce pellet
hardness. These problems increase as the fat level increases and
become severe when the added fat exceeds 6% of the feed. Added
fat reduces dustiness and therefore improves the environment in
swine buildings.
Certain biological effects also can be expected when fat is
added to diets of starting, growing and finishing pigs. These
include: improved palatability, reduced feed consumption, signi-
ficant improvement in feed efficiency, slight increase in growth
rate, increased carcass fatness at high fat levels and high lev-
els of vegetable oils causing a softening of carcass fat.
Pigs' responses to fat may be greater in warm or hot
environments than in cool environments. Fat has a lower heat
increment than carbohydrates and proteins and is less likely to
cause reduced feed intake during heat stress.
When fat is added to a swine diet, the amount of feed con-
sumed usually decreases. However, animals' needs for other
nutrients remain relatively constant when expressed on a daily
basis. Therefore, to maintain performance when fat is added to
the diet, the concentration of other nutrients should be
increased.
The decision to add fat is an economic one. If improvement
in growing-finishing swine preformance more than offsets the cost
of adding fat, it is economical. Typically, adding 1% fat to the
diet results in approximately 2% better efficiency.
When the piglet survival rate is below 85%, supplementing
the sows' diet with fat during late gestation may improve sur-
vival rate. The added fat must provide at least 2.0 lb. to 2.5
lb. of fat to each sow prior to farrowing. This appears to be a
response to fat and not to increased energy intake. The added fat
increases the fat content of the colostrum and milk which is
responsible for the increased survival rate. Adding fat to lacta-
tion diets increases voluntary ME consumption, but only slightly
reduces the weight loss in the sows. It increases weaning weights
of the litters due to increased fat in the milk. There is no evi-
dence that added fat improves subsequent reproductive preformance
of sows.
Fiber Content
Some energy sources are relatively high in fiber and reduce
gain and efficiency if fed at excessive levels. Pigs 40 lb. and
heavier usually can tolerate up to 5% of a high-fiber feed such
as alfalfa in their diet without a noticeable effect on perfor-
mance. As pigs mature, more and more low energy-high fiber feeds
can be fed, especially to sows during gestation and post-weaning.
Fiber feeds such as wheat bran and beet pulp may be useful in
gestation and farrowing diets because of their laxative effects,
but should constitute no more than 5% of a lactation diet.
Fiber has a high heat increment and during cold stress this
heat can be utilized to maintain body temperature, thus, less is
wasted. Therefore, there is a smaller difference in relative
values between fibrous grains (such as barley or oats) and corn
in cold weather. Conversely, in hot weather the high heat incre-
ment becomes a problem for the pigs' cooling ability.
Moisture Content
High-moisture grains contain less energy per pound of feed
because of the water content. More pounds of high-moisture grain
must be used to get the same amount of dry matter. Studies with
high-moisture grains fed in complete diets indicate similar per-
formance to dried grain when efficiency is measured on a dry
matter basis. Free-choice feeding of grain and supplement often
results in poorer efficiency. See PIH-73, High Moisture Grains
for Swine.
Grinding
With the exception of high-moisture corn, grinding improves
feeding efficiency for all grains, especially high-fiber grains
such as oats or barley. Finer grinding usually results in
improved efficiency, although finely ground corn increases the
incidence of ulcers in finishing swine. Fine grinding is most
advantageous for pigs under 40 lb. Wheat is very palatable when
it is medium to coarsely ground in complete rations since high
levels of finely ground wheat in diets has been associated with
lowered palatability due to pastiness of the meal. See PIH-71,
Physical Forms of Feed.
Pelleting
Pelleting a diet may increase gains by 5% and feed effi-
ciency by 5% to 10%. A high-energy cereal such as corn or sorghum
benefits less from pelleting than fibrous feeds like barley or
oats. When a complete diet is purchased, pelleted diets may be
more economical than meal diets. However, the advantage of pel-
leting probably will not offset the cost of hauling grain from
the farm to a pelleter and home again.
Relative Value
In selecting energy sources for swine diets, also consider
protein quality and content. Because the amino acids lysine,
tryptophan, threonine and methionine can be limiting in swine
diets, levels of these amino acids on cereal grains affect their
overall value. Although sugar, molasses and fats or oils are
energy sources, they provide little or no protein to the diets.
The amount of feed per unit of gain is not the most impor-
tant factor in swine nutrition. Cost per unit of gain is more
important; therefore, it is necessary to use the most economical
feed sources available in swine diets. The relative feeding
values shown in Tables 1 and 2 can be used to determine which
ingredient is most economical. For example, if corn costs 5.0
cents per pound, barley is worth about 4.5 cents per pound (5.0
cents x 90%). If barley can be purchased for less than this, it
is a better buy.
______________________________________________________________________
Table 1. Relative feeding values of energy sources1.
_________________________________________________________________
Metabo- Relative Maximum recommended
lizable feeding percent of complete
diets3
energy value vs. Gesta- Lacta-
Ingredient (air dry) kcal/lb. corn,% 2 tion tion
__________________________________________________________________
Alfalfa meal dehydrated 775 70-80 50 5
Alfalfa meal sun-cured 800 60-70 50 5
Animal fat stabilized 3585 185-210 10 6
Bakery surplus material 1650 95-110 40 40
Barley (48 lb/bu) 1380 90-100 80 80
Beet pulp, dried 1020 70-80 10 5
Brewers dried grains 1000 90-100 40 5
Buckwheat 1200 80-90 50 0
Corn yellow 1550 100 80 80
Corn (high lysine) 1520 100-105 90 90
Corn and cob meal 1300 80-90 70 0
Corn distillers dried grains 1540 115-130 40 10
with solubles
Corn gluten feed 1285 74 90 5
Corn grits by-product (hominy)1400 100-105 60 60
Emmer 1140 80-90 20 0
Sorghum grain (milo)4 1480 95-100(4) 80 80
Millet (Proso) 1230 90-95 80 80
Molasses (77% D.M.) 1060 55-65 5 5
Oats (36 lb/bu) 1240 85-95 80 5
Oat groats 1550 115-125 0 0
Potatoes (22% D.M.) 370 20-25 80 0
Rice grain 1070 75 40 0
Rye 1300 90 20 0
Spelt 1180 85 40 0
Sugar 1383 70-80 0 0
Triticale 1450 90-95 80 80
Wheat, hard 1475 100-105 80 80
Wheat, soft 1500 90-95 80 80
Wheat, high protein 1500 100-105 80 80
Wheat bran 980 60-65 30 5
Wheat middlings 1340 125-140 30 5
Wheat, dried 1405 135-145 5 5
__________________________________________________________________
Contd ...Table 1.
_________________________________________________________________
Maximum recommended
percent of complete diet3
Starter Grow- Remarks
Ingredient (air dry) finish
__________________________________________________________________
Alfalfa meal dehydrated 0 5 Good source of B vitamins
Alfalfa meal sun-cured 0 5 Unpalatable to baby pigs
Animal fat stabilized 5 10 High energy, reduces dust
Bakery surplus material 20 40 High energy, variable salt
content
Barley (48 lb/bu) 25 85 Corn substitute, lower energy
Beet pulp, dried 0 0 Bulky, high fiber, laxative
Brewers dried grains 0 10 High fiber, B-vitamin source,
low lysine
Buckwheat 0 50 Not to light colored pigs
outdoors
Corn yellow 60 85 High energy, low lysine
Corn (high lysine) 60 90 Lysine analysis recommended
Corn and cob meal 0 0 Bulky, low energy
Corn distillers dried grains 5 10 B-vitamin source, low lysine
with solubles
Corn gluten feed 5 25 Low lysine
Corn grits by-product (hominy)0 60 Subject to rancidity
Emmer 0 0
Sorghum grain (milo)4 60 85 Low lysine
Millet (Proso) 60 85 Low lysine
Molasses (77% D.M.) 5 5 Low energy, partial grain
substitute
Oats (36 lb/bu) 0 20 Low energy, partial grain
substitute
Oat groats 20 0 Palatable
Potatoes (22% D.M.) 0 30 Must be cooked, low protein
Rice grain 0 20 Low energy, low lysine
Rye 0 25 Possible ergot toxicity, low
palatability
Spelt 0 25 Low energy, low lysine
Sugar 5 0 High palatability, no protein
Triticale 20 85 Possible ergot
Wheat, hard 60 85 Low lysine
Wheat, soft 60 85 Low lysine
Wheat, high protein 60 85 Low lysine
Wheat bran 0 0 Bulky, high fiber, laxative
Wheat middlings 0 10 Partial grain substitute
Wheat, dried 20 5 High lactose content, variable
content
____________________________________________________________________
1Based on an air dry basis unless otherwise noted. High moisture
feedstuffs must be converted to an air dry equivalent of 88-90%
dry matter to determine energy and substitution rates. Complete
data on all ingredients are not available.
2When fed at no more than maximum recommended % of complete
diets. Relative values based on metabolizable energy, lysine and
phosphorus content using simultaneous equations. Example:
ME Lysine Phosphorus Price
___________________________________________________________
1550X + .024Y + 0.25Z = $/cwt. corn
1460X + 2.90Y + 0.60Z = $/cwt. soybean meal (44%)
0X + 0Y + 18.50Z = $/cwt. dicalcium phosphate
Determine values for X, Y, and Z and multiply them times the M.E.
(kcal/lb), % lysine, and % phorphorus of feed in question and sum
the values.
3Higher levels may be fed although performance may decrease.
4Some bird resistant sorghums are 80-90% vs. corn.
______________________________________________________________________
______________________________________________________________________
Table 2. Relative feeding values of protein sources1.
_____________________________________________________________________
Metabo- Relative Maximum recommended
lizable feeding percent of complete
diets3
energy value vs. Gesta- Lacta-
Ingredient (air dry) kcal/lb. 44% soybean,%2 tion tion
_____________________________________________________________________
Blood meal, flash dried 1200 185-200 5 0
Buttermilk, dry 1400 75-85 0 5
Canola meal (solvent) 1200 75-85 5 5
Corn gluten meal 1395 40-60 5 5
Cottonseed meal, solvent 1150 65-75 5 5
Distillers dried solubles 1180 65-70 5 5
(corn)
Feather meal, hydrolyzed 1000 60-70 3 3
Fish meal, anchovy 1120 140-165 5 5
Fish meal, menhaden 1500 140-165 5 5
Fish solubles (50% solids) 780 50-60 3 3
Linseed meal 1280 55-65 5 5
Meat and bone meal 1035 95-110 10 5
Peanut meal, expeller 1400 70-80 5 5
Skim milk, dried 1620 95-100 0 0
Sorghum gluten meal 1460 40-55 5 5
Soybeans, whole, cooked 1640 90-100 30 25
Soybean meal, solvent 1460 100 25 20
Soybean meal, solvent, 1535 110-112 22 18
dehulled
Tankage (meat meal) 980 115-130 10 5
Yeast, brewers dried 1400 100-105 3 3
______________________________________________________________________
Contd ..Table 2.
______________________________________________________________________
Maximum recommended
percent of complete diet3
Starter Grow- Remarks
Ingredient (air dry) finish
______________________________________________________________________
Blood meal, flash dried 5 5 Low isoleucine, unpalatable
Buttermilk, dry 20 5 Good amino acid balance
Canola meal (solvent) 5 10 Toxic problem at high levels
Corn gluten meal 0 5 Low lysine
Cottonseed meal, solvent 0 5 Gossypol toxicity, low lysine
Distillers dried solubles 5 5 B-vitamin source, low lysine
(corn)
Feather meal, hydrolyzed 0 3 Low lysine
Fish meal, anchovy 5 5 Excellent amino acid balance
Fish meal, menhaden 5 5 Excellent amino acid balance
Fish solubles (50% solids) 3 3 Excellent amino acid balance
Linseed meal 5 5 Low lysine
Meat and bone meal 5 5 Low lysine, tryptophan and
methionine, good phosphorus
Peanut meal, expeller 0 5 Low lysine
Skim milk, dried 20 0 Excellent amino acid source,
palatable
Sorghum gluten meal 0 5 Low lysine
Soybeans, whole, cooked 40 30 Similar to soybean meal, but
may produce soft pork
Soybean meal, solvent 35 22 Similar to soybean meal,
dehulled
Soybean meal, solvent, 30 20 Good amino acid balance with
dewhulled corn
Tankage (meat meal) 0 5 Low digestibility, unpalatable
Yeast, brewers dried 3 3 Source of B-vitamins
_____________________________________________________________________
1Based on an air dry basis unless otherwise noted. High moisture
feedstuffs must be converted to an air dry equivalent of 88-90%
dry matter to determine energy and substitution rates. Complete
data on all ingredients are not available.
2When fed at no more than maximum recommended % of complete diet.
Relative values based on metabolizable energy, lysine and
phosphorus content using simultaneous equations. Example:
ME Lysine Phorphorus Price
___________________________________________________________
1550X + 0.24Y + 0.25Z = $/cwt. corn
1460X + 2.90Y + 0.60Z = $/cwt. soybean meal (44%)
0X + 0Y + 18.50Z = $/cwt. dicalcium phosphate
Determine values for X, Y, and Z and multiply them times the M.E.
(kcal/lb), % lysine, and % phosphorus of feed in question and sum
the values.
3Higher levels may be fed although performance may decrease.
_____________________________________________________________________
______________________________________________________________________
List of Figures:
Figure 1: Partition of energy in nutrition.
REV 6/91 (5M)
______________________________________________
Cooperative Extension Work in Agriculture and Home Economics,
State of Indiana, Purdue University and U.S. Department of Agri-
culture Cooperating. H.A. Wadsworth, Director, West Lafayette,
IN. Issued in furtherance of the Acts of May 8 and June 30, 1914.
It is the policy of the Cooperative Extension Service of Purdue
University that all persons shall have equal opportunity and
access to our programs and facilities.