H
opefully you read the labels on the feed bags or the feed tags attached to the bag. Those ingredients
listed are the products that go into your feed. Each of those feed ingredients has a legal definition
that defines stage of growth, preparation and end use. So let us look at the legal definitions for some
common feedstuffs used for cecal -fermentation ,nonruminant animals (horse, rabbits, guinea pigs, and chinchillas).
ALFALFA MEAL
A
lfalfa meal is made from the chopped or cut forage which is either sun-cured or hot-air dried. There
is a difference in the quality between sun-cured and hot-air dried alfalfa. Sun-cured is left in the
field until it is dry enough to be processed. Then it is raked up, loaded into a truck and taken to
the processing facility. Hot-air dried alfalfa is cut and trucked directly to the processing facility.
Each time the alfalfa is handled, nutritional losses will occur. So hot-air dried alfalfa is better quality
from the start.
Processing of alfalfa meal
D
ehydrated alfalfa is produced by loading the raw material into a rotating, heated drum dryer. The dryer
takes 3-5 minutes to evaporate the moisture. A pneumatic air system then evacuates the concentrated dry
matter into a hammer mill. The alfalfa is ground to a uniform particle size, then it is compressed
into a pellet. The pellet is steamed to lubricate its way through a die. The pellets are allowed to cool
before being stored in tanks containing inert gas(nitrogen). The nitrogen gas preserves the vitamins
K and E, carotene and xanthophyll from oxidation.
Anti-nutritional factors in alfalfa
T
here are anti-nutritional factors (natural toxins) in alfalfa-saponins, tannins and coumestral. Saponins
have a bitter taste and will irritate the lining of the mouth and intestine.They can cause slobbering.
This is something to consider if you have a wide spread outbreak of slobbering in your herd. Not all
slobbering animals have tooth problems.
Coumestral is an estrogenic substance. It acts in the same way as zearalenone (mycotoxin) and Ralgro (steriodal growth promoter (legal only for cattle and sheep). Alfalfa meal use in sow diets has declined
due to the possible effects of coumestral on reproductive performance. This is
something to think about in regards to other livestock reproductive performance problems.
Alfalfa meal also contains tannins. Tannins and trypsin inhibitors bind proteins and inhibit
protein digestion. They can be removed from the feed but it is not cost effective.
SOYBEAN MEAL
Soybean meal is the best protein source for livestock feed. It has a well-balanced amino acid
ratio, high palatability and is economical per unit cost. There are several problems with soybean
meal. It is a good source for lysine and tryptophane but a poor source for methionine. Methioine
is a very important sulfur-bearing amino acid, essential for wool, hair and fur growth. There
has been work done on the fur bearing animals (mink and fox) that soybean meal is a good protein
source for them. Excessive amounts of soybean hulls (very high fiber) was not good for meat
rabbits but regular soybean meal was very acceptable as a rabbit feed.
Anti-nutritive factors in soybean meal
Soybeans must be “cooked” or heat-treated There are several anti-nutritive factors in soybeans.
Soybeans must be heat-treated at 215F for 15 minutes. This destroys the trypsin and chymotrypsin
inhibitor-protease. You still have saponins, tannins, lectins, goitrogens (thyroid inhibitors) and
phylates causing trouble. Phylates are naturally occurring phosphorus and inositol compounds.
Phylate combines with zinc, iron and manganese to reduce the bioavailability of those metals. It
is a metal chelating factor. You can supplement with calcium, phosphorus and zinc or add the
enzyme phytase to liberate the phosphorus from the phylate compound.
There are haemagglutins/lectins that vary in the effect on species. Rabbits and rats seem to be
more sensitive to these red blood cell clumping agents. The proteinaceous products also bind with
the cells of the intestinal mucosae causing nutrient malabsorption problems. Saponins are
glycosides that cause a bitter taste and have a haemolytic effect on red blood cells. Goitrogenic
factors or isoflavinic glycosides can result in the enlargement of the thyroid and the reduction
in thyroxine activity. Bad news for hypothryoid patients. The final problem is a headache mainly
for turkey producers. Rachitogenic factors interfere with the calcification of bone-mainly in
turkeys.
Soybean meal processing
After harvesting, soybeans are cleaned and dried. Then the beans are cracked into small pieces by
a corrugated roller. This prepares them for oil extraction. You have to separate the hull from the
“meat”. Air aspirators, screen or centrifuges are the common ways to separate the pieces.
Then the “meat” is steam-heated to 215F and run through a roller mill to create soybean flakes.
These flakes provide a greater surface area for the solvent (hexane or ethanol) to extract the
oil. The solvent and crude soybean oil is drawn off by a pump and distlled into the pure soybean
oil.
The wet soybean flakes and remaining solvent must be separated. The flakes are toasted at a high
temperature to improve the nutritional value. The hulls may now be added back to the flake
mixture. The addition of the hulls to the flakes will lower the protein content from 49-50% to a
standardized 44% protein and up to a maximum of 7% crude fiber.
Then the cooled and dry soybean mixture is ground up into a meal. Since soybean meal is very
unstable, most feed processors will keep the soybeans intact until there is demand for them. So
they don’t usually keep soybean meal on hand.
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