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Feed Management as a Tool for Manure Nutrient Reduction
Purchased
feeds or feed ingredients create the major portion of livestock farm nutrients
that, if not removed as animal products (meat, milk, eggs),
manure, or effectively recycled as fertilizer for a cropping program, can result
in a whole farm nutrient imbalance leading to problems such as water quality.
Several feed management practices however, can be used to reduce nutrient
excretion by animals and potentially reduce manure nutrients by up to 40
percent. These might include precision feeding (phase feeding, splitsex or group
feeding), feed processing, feed additives, feed resources, crude protein
reduction with the addition of synthetic amino acids, reduction of dietary
phosphorus to the amount actually needed by the animal, use of phytase, use of
more highly digestible feed ingredients, i.e., sources of available P and N, and
routine feed analyses and diet formulation.
Precision feeding is the practice of changing the level of available nutrients
fed to the animal based on age and level of production. Decreasing dietary
protein level as the animal matures and protein needs lessen decreases excess
protein that would be eliminated in the manure.
Split sex or group feeding is the practice of feeding animals of the same type,
sex, size, or production level similar diets or amounts. This eliminates a need
to “over feed” for the production of animals that require higher nutrient
levels. This over feeding is a source of many of the excess nutrients produced
on animal operations.
Feed processing changes the form of the feed in some manner through grinding,
steam flaking, pelleting, ensiling, or other methods which makes the nutrients
of the various feedstuffs more available. The simple act of grinding grain
increases surface area for enzyme digestion and the likelihood that the feed
nutrients will be in the digestive tract a sufficient amount of time for
absorption, whereas they might be expelled in the manure virtually unchanged if
they were fed as whole grain. Ensiling, pelleting, and steam flaking can all
increase the digestibility or absorbability of feed nutrients, decreasing the
likelihood that they will be excreted.
Feed additives such as enzymes, agonists, or other growth promotants and amino
acids can increase the digestibility or absorption of nutrients. Phytase is an
enzyme that when added to feed, can increase the digestibility of organic
phosphorus. Phytase application with a corresponding decrease in supplemental
inorganic phosphorus has been shown to reduce manure phosphorus excretion by up
to 40 percent in poultry and swine.
Feed resources are genetically enhanced grains, by-product feeds, new or
alternative grains, and feedstuffs produced on the farm where the manure will be
deposited. Feed resources that are new to the animal operation can be utilized
to provide for the nutrient needs of the animal, and also decrease the nutrient
output in the manure. New varieties of grain have been produced that contain a
large percentage of available phosphorus. These grains can reduce manure
phosphorus by as much as 40 percent in poultry and swine.
Feed management is one of the six core elements of the Comprehensive Nutrient
Management Plan (CNMP). A conservation practice standard was adopted by NRCS in
2003, making feed management eligible for voluntary conservation financial
assistance programs. In 2004, NRCS signed a Memorandum of Understanding with the
American Registry of Professional Animal Scientists to certify technical service
providers (TSPs) in the area of feed management. TSPs working in this area and
certified by ARPAS as experts will be able to assist farmers in making feed
management decisions and in developing the feed management element of the
operation’s CNMP.
Your contact is Glenn Carpenter, National NRCS Animal Husbandry Leader, at
301-504-2208, or
glenn.carpenter@usda.gov.
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