The manager of a feed company in China on Monday said it's common practice to add melamine — a chemical used to make fertilizers and plastics — to farm feed, but he claimed that in proper doses it will not harm animals.

"We've been running the melamine feed business for about 15 years and receiving positive responses from our customers," Wang Jianhui, manager of the Kaiyuan Proten Feed company in Shijiazhuang, told the Associated Press.

Melamine is rich in nitrogen and can boost nitrogen levels, creating the illusion of higher protein levels in quality tests.

In mid-March, Ontario-based Menu Foods recalled 60 million cans and pouches of its "cuts and gravy" dog and cat food manufactured at two U.S. facilities between Dec. 3, 2006, and March 6 after it received a number of complaints from customers.

The FDA in March blocked imports of wheat gluten from the Xuzhou Anying Biologic Technology Development Co. after finding melamine in samples of recalled wet and dry pet food and treats. The chemical was also found in cats who died after eating the contaminated food.

Researchers at the University of Guelph on Friday said the pets who ate the recalled food likely developed crystals in their kidneys because of a reaction between cyanuric acid in their urine and melamine.

The FDA has confirmed 16 animal deaths in the U.S. related to the pet food recall.

Canada's food watchdog issues border lookouts

Meanwhile, Canada's food watchdog has issued border lookouts for vegetable proteins destined for human food coming into the country from China.

"We will subject the shipments to testing and the shipment will be held until the results of the test clear it in terms of the absence of the contaminant," said Paul Mayers, a spokesman for the Canadian Food Inspection Agency.

Vegetable proteins are commonly used in a wide range of food products, including baby formula, pizza dough and hot dog wieners.

The CFIA also confirmed that a B.C. mill last July received a shipment of wheat gluten from the same Chinese company that supplied the tainted wheat gluten to the pet food manufacturers. The B.C. mill used the gluten as food for fish farms. Still, the CFIA says the risk to consumers is low.

Food scientist Mansel Griffiths at the University of Guelph's Canadian Research Institute for Food Safety said that Canada must take an active approach in dealing with Chinese suppliers.

"[We should] work with the Chinese government, work with the manufacturing industry in China to try and bring them up to the standards that we expect of Canadian companies," he said.

With files from the Associated Press