Campus News

Published by Communications and Public Affairs (519) 824-4120, Ext. 56982 or 53338

News Release

September 23, 2002

New study on pigs, phosphorus may help environment

Pigs are better at digesting phosphorus than previously thought, new research by University of Guelph scientists shows. The findings could have major implications for the environment, as farmers may be needlessly supplementing animal feed with the inorganic mineral, contributing to water pollution problems.

The research, headed by Ming Fan, a professor in the Department of Animal and Poultry Science, shows that pigs are absorbing about 25 per cent more phosphorus from conventional soybean meal and about 35 per cent more phosphrous from regular corn than has been previously reported. Phosphorus is a key component in the proper bone development and health of growing pigs, but there is a large variation in phosphorus availability in key feed ingredients, Fan said. Currently, swine diets are formulated with a big safety margin to compensate for this variation. In addition, phytate phosphorus, the major form of phosphorus in cereal grains and oil seed meals, is not thoroughly digested by pigs. As a result, swine producers, thinking that their animals aren’t absorbing enough phosphorus, often supplement pigs’ diets with the expensive nutrient to ensure adequate growth.

The result is high phosphorus levels in pigs’ fecal matter, which is one of the reasons that animal waste is the leading source of phosphorus pollution from agriculture. Phosphorus pollutes surface and groundwater and promotes the growth of algae in rivers, lakes and streams, reducing available oxygen to fish and aquatic life.

“These aspects – cost and pollution – have made research on improving efficiency of phosphorus utilization by pigs one of the most important issues in swine nutrition,” Fan said.

Already, research has looked at adding a phytase-producing gene to corn and soybean varieties to boost absorption, and University of Guelph researchers developed “enviropigs,” animals that are genetically modified so their bodies can absorb a normally indigestible form of phosphorus. The fecal phosphorus levels in enviropigs are 56 to 75 per cent lower than those of regular pigs.

Fan’s research may also help reduce fecal phosphorus levels by encouraging animal nutritionists and farmers to reconsider the formulation of pigs’ diets and cut down on inorganic supplements. His research team developed a method that, for the first time, take into account the amount of phosphorus that is naturally secreted by pigs in their gastrointestinal tract (endogenous phosphorous loss). The new method corrects for this endogenous phosphorus loss when determining how much phosphorus a pig is actually digesting.

“A scarcity of information exists concerning the true digestibility values and the
endogenous phosphorus outputs in pigs,” Fan said. “Our research shows that we have been underestimating digestive utilization of phosphorus in soybean and corn, major feed ingredients in commercial swine diets around the world.”

The findings are also good news for the industry in terms of financial costs, as
phosphorus is the third most expensive nutrient after energy and protein in swine nutrition and feeding. Support for the study included grants from the Natural Sciences and Engineering Research Council of Canada), Ontario Pork Producers’ Marketing Board, Ontario Pork, Agriculture and Agri-Food Canada, Ontario Ministry of Agriculture and Food, and Canadian Pork Council.

Other Guelph researchers involved in the study include Yingran Shen, Tania Archbold, Ayodele Ajakaiye, Dale Lackeyram, Todd Rideout, Yingxin Gao, Kees de Lange and Roger Hacker.

Ming Fan
Department of Animal and Poultry Science
(519) 824-4120, Ext. 3656

For media questions, contact Communications and Public Affairs, (519) 824-4120,
Ext. 3338.

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