Researchers have unraveled another part of the riddle about how to manage hog manure.
They found that a controlled diet can greatly reduce the amount of manure produced. Control of a hog’s diet can also curb the amount of hydrogen and phosphorus excreted.
The research was done at Agriculture Canada’s research centre at Brandon, Man. The findings are important when anticipating the rapid growth expected in Western Canada’s swine industry, said swine nutritionist Raja Grandhi.
“There is a lot of public concern, about the odor mainly, and also the possible contamination of water.”
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The study of the effects of feeding hulless barley versus hulled barley found that pigs on hulless diets produced about one third less manure.
“Hulless barley is digested more,” said Grandhi. “More energy and nutrients are absorbed and less excreted.”
Researchers went a step further by feeding hulless barley with no protein supplements. Instead, they balanced the diet using amino acids and a digestive enzyme.
The amino acids (lysine, threonine, methionine and tryptophan) curbed the amount of nitrogen excreted in swine manure by close to 30 percent compared to a diet of hulless barley and soybean.
Adding phytase, a digestive enzyme, reduced the amount of phosphorus excreted in manure by about one third in diets with hulled barley. In the hulless diets, the enzyme supplement caused a 45 percent drop in phosphorus levels.
“The phytase made enough phosphorus available to the animal to grow normally,” said Grandhi. “At the same time, it reduced the phosphorus excretion.”
Nitrogen and phosphorus found in swine manure can be a valuable fertilizer when applied to agricultural land. However, there’s a risk of excess nutrients leaching into surface and ground water supplies.
That might happen, according to Agriculture Canada, when there are large swine units with a limited land base on which to apply hog manure. It could also happen if manure is applied at rates exceeding crop needs.
Researchers plan to continue studying the merits of hog diet management using amino acids, enzymes and other feed supplements. Grandhi said the goal is to develop guidelines for nutrient management that can be released to swine producers in a few years.
The Brandon research centre has also tested a yucca plant extract to curb manure odors. Ammonia, carbon dioxide and hydrogen sulfide are among the byproducts of hog manure.
There are two kinds of yucca plant extracts available, said Grandhi.
“One you add to the diet to feed the pigs. One you add to the manure in the barn. We tried both to see how it works.
“Feeding the product really doesn’t reduce the odor that much,” Grandhi said. “But when you add this product to the manure, there is a reduction in the smell.”
