17 / 40
August 2016 17
Pork News & Views
August 2016
Back to the Basics of Feeding Pigs
Reliable nutritional information, whether
from book values or laboratory analysis, is
important to determine what diet will meet
a pigs’ requirements to grow, reproduce,
produce milk, fatten or maintain its weight
depending on stage of life. This informa-
tion can be obtained from a laboratory feed
analysis. Many producers use book values
instead of getting a laboratory analysis.
When comparing these, laboratory values
are more accurate, representing the actual
values of each nutrient. For example, lysine
levels are often estimated by analyzing for
crude protein. Both wet chemistry and near
infrared spectroscopy (NIRS) are methods
commonly used to obtain parameter values.
Wet chemistry measures the nutritional value
by drying the ingredient, followed by the use
of heat and chemicals. For example, Neutral
Detergent Fiber (NDF) is the fiber portion
that is not broken down when boiled in a
neutral pH solution.
NIRS estimates the nutritional value of
the feed using light reflection rather than
chemistry to identify and measure amounts
of compounds in a sample. The reflectance
values are entered into calibration equations,
which estimate nutrient values based on a
large database determined by wet chemistry.
This method is commonly used for obtain-
ing crude protein, moisture, crude fiber, ash
and fat. This provides fast, reproducible and
cost- effective results with minimal sample
preparation by the laboratory.
Each laboratory will have a set of packages
available to obtain various parameters based
on the customer’s needs. Of course the
analysis is only as good as the sample submit-
ted to the laboratory. A good sample should
be representative of the entire feedstuff sent
in for testing. To do so, grab samples from
multiple spots and mix them to create a com-
posite sample, and then obtain a sub sample
for the testing.
The following are explanations of the terms
found on a laboratory report.
Dry Matter
Each feed analysis report specifies the dry
matter and moisture of the feed analyzed.
The dry matter is the moisture free material
left after drying the sample. Moisture dilutes
the concentrations of the nutrients present,
and it is standard practice to evaluate the
feed and balance rations using a dry matter
basis. High moisture ingredients may not just
affect the concentration of nutrients, it also
creates a difficulty when incorporating the
ingredient into a practical feeding program.
Nutrients present can be classified into five
main groups; energy, protein, minerals and
vitamins, with the fifth one being water.
Protein
Crude protein (CP) is calculated and based
on the nitrogen content of the feedstuff. The
soluble portion of crude protein is most read-
ily available to animals. This consists of small
amino acid chains, or non-protein-nitrogen.
Protein is made up of approximately 16%
nitrogen and, in the lab, total nitrogen is
measured and multiplied by 6.25 (100/16) to
report it on a “crude protein” basis. Without
looking at the type of protein CP is made up
of, it gives no information on the amino acid
content or its availability. It plainly indicates
that it contains nitrogen, including both true
protein that contains amino acids (the build-
ing blocks of protein) and non-protein-nitro-
gen (NPN). NPN includes urea and ammonia
that contain nitrogen.
There are 10 amino acids categorized as ‘es-
sential amino acids’ which the animal cannot
synthesize, or not at a rate to meet the ani-
mal’s needs. They are Phenylalanine, Valine,
Threonine, Tryptophan, Isoleucine, Methio-
nine, Histidine, Arginine, Lysine and Leucine.
Since lysine is the most limiting amino acid
for pigs, it is used to formulate a diet allowing
some amino acids to be in excess. The re-
mainder of the amino acids requirements are
expressed as a ratio to lysine and added via
protein or synthetic sources. Non-essential
amino acids can be synthesized by the animal
since they have the ability to convert surplus
amounts of one amino acid to another to
meet its needs through complex processes
completed by enzymes. Nevertheless, both
essential and non-essential amino acids are
needed for the animal to thrive.
Energ y
Energy is obtained from lipids (fats and oils),
protein, and carbohydrates such as starch,
sugar and fiber. The two primary sources
of energy in swine diets are carbohydrates
and lipids. Energy from protein is utilized
when protein is in excess to the animal’s
requirements. However, excessive amounts
of protein not utilized to its full potential
are expensive, may affect feed efficiency and
creates excess nitrogen which is excreted
into the environment. Energy is calculated
and reported as gross energy (GE), digest-
ible energy (DE), metabolizable energy (ME)
or net energy (NE) and are very important
contributors to the diet to reduce cost while
maximizing pig performance. As shown by
the NRC in Figure 1, the gross energy refers
to the total energy available in a feed. This is
then fragmented into DE where the energy
of faeces is removed, followed by ME, where
the energy for urine and combustible gases
is subtracted off of DE to obtain ME. NE
accounts for the thermal losses and can be
divided according to its utilization; mainte-
nance (NEm) or production (NEp), which in-
cludes growth, gestation and lactation. NE is
mostly used by nutritionists as it’s ingredient
dependent; being lower for protein and fiber,
but higher for fats and starches. However, DE
is probably most likely to be understood and
used by producers. If highly digestible ingre-
dients are used, the values for DE and ME will
Figure 1. Components of energy in a diet (NRC).