Ammonia Control for Animal
Housing Systems with Liquid Manure -
Diet Manipulation
| Pro |
Con |
| Source control strategy |
Limited to strategies that can maintain performance |
| Potentially less costly than post-excretion strategies |
Relatively new research field |
Minimization of nitrogen (N) excretion is
the most obvious method to curb ammonia emissions. By reducing
the amount of nitrogen excreted, less ammonia will be formed
and volatilized. When common feeds are included in the diet,
protein sources are added to meet animal needs for lysine, typically
the most limiting amino acid. All other amino acids are consequently
supplied in excess and excreted.
The most promising dietary manipulation consists of supplying
non-ruminants with the amino acids they need, including crystalline
ones, instead of supplying feeds based on crude protein. In the
ruminant animal, meeting the needs of the rumen, independently
of the lower digestive tract, effectively reduces the content of
dietary crude protein. In swine, dairy, and poultry, nitrogen excretion
is reduced by approximately 8.5 to 10 percent for each one-percentage
unit reduction in dietary crude protein. Greater reductions are
possible and, in fact, direct emissions of ammonia are reduced
by 19 percent for every percentage unit of dietary crude protein
that is reduced in swine diets. As animals are fed closer to true
nitrogen requirements, further reductions in dietary protein may
result in less pronounced reduction in nitrogen excretion and ammonia
losses.
Addition of fermentable carbohydrates, such as bran or pulp, into
grow-finishing diets, resulted in a 14 percent reduction of ammonia
emissions for each increase in carbohydrate. More work evaluating
the balance of carbohydrate and protein in diets is needed. The
reduction may be due to a pH effect, to the shift from urinary
to fecal nitrogen excretion, or both. Additives that bind ammonia
have shown reductions in ammonia emissions (26 percent over a period
of seven weeks in swine fed a yucca extract).
Lysine is economical for both swine and poultry diets. By-products
are important economical sources of rumen protein for ruminants.
Therefore, some dietary strategies do not increase diet costs to
the producer. Further protein reductions will increase ration costs,
by may be considered affordable, depending on the operational objective
of each producer.
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