Scientists at the Agriculture Canada Research Centre in Brandon, Man., have shown it is possible to reduce many problems associated with swine manure by decreasing the amounts of nitrogen and phosphorus excreted.
This was achieved by using amino acid and enzyme supplements in place of protein supplements with diets based on conventional or hulless barley. Producers can use the new information to formulate diets that help minimize the impact of swine manure on the environment.
Since April 1997, the research centre has conducted several precision-feeding and metabolism studies with grower-finisher pigs to find ways of reducing nutrient losses and odor emissions from swine manure.
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The main findings of this work indicate:
- Feeding hulless barley increases the digestibility of dietary energy and reduces the output of manure on a dry matter basis by about 33 percent, compared to feeding hulled barley.
- Feeding hulless barley-based diets having no protein supplement but being balanced for necessary amino acids (lysine, threonine, methionine and tryptophan) reduces the amount of nitrogen excreted in swine manure by about 28 percent, compared to feeding standard hulless barley/soybean-based diets.
- Adding phytase, a digestive enzyme for organic phytate-phosphorus, reduces the amount of phosphorus excreted in swine manure by about 35 percent for hulled barley-based diets and about 45 percent for hulless barley-based diets.
- Using a combination of amino acid and enzyme supplements, as tested in these studies, reduces both phosphorus and nitrogen losses from swine manure.
- Feeding a yucca plant-based extract during the grower-finisher period does not reduce the intensity of manure odors. However, adding this extract to feed and manure tends to reduce odor intensity of manure from pigs on hulled barley-based diets.
After odor control, the major concern among the public when it comes to hog barns is water pollution. Nitrogen and phosphorus increase the fertilizer value of swine manure for crop production.
However if too much is applied to fields, these nutrients could move into surface and ground water. This may happen where large swine units are set up in areas with a limited land base to apply manure or where application rates exceed crop requirements.
As well, nitrogen and phosphorus in some feeds are not readily digested by pigs, and undigested amounts will be excreted.
Formulating a well-balanced diet with digestible feed and the proper levels of amino acids may reduce excretion losses of these nutrients. Using appropriate feed and manure additives may also help control odor.
For more information contact Raja Grandhi, manure management researcher, Brandon Research Centre, 204-726-7650.
