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by Nancy Carver Singleton Phosphorous can be reduced substantially in feedlot rations without harming performance, according to a University of Nebraska (NU) study. Although excess phosphorous does not hurt cattle, it is an additional cost and an environmental concern. Feedlot calves and yearlings in the study were fed 60 percent less phosphorous than is typically fed in the beef industry. In fact, researchers could not create a diet low enough to see any effect on the animals, said Terry Klopfenstein, an animal scientist who conducted the trials. The study also looked at how reduced dietary phosphorous lowered the amount of phosphorous in manure. Researchers found that reducing phosphorous 34 percent for calves and 44 percent for yearlings lowered phosphorous in manure by 38 percent and 59 percent respectively. One problem, Klopfenstein said, is that it is difficult to formulate rations low in phosphorous since corn itself contains more than the needed amount. "We cannot feed economical foodstuffs as low as the requirement. That is a challenge. An even bigger challenge is some by-product feeds, primarily from the ethanol industry, have even more phosphorous. As we use those, we are feeding more phosphorus in feedlots than cattle need," Klopfenstein said. The study confirms that cattle do not need phosphorous supplements, which are still used in many feedlots. "Most producers believe you need quite a bit of phosphorus. It takes time to change those attitudes," Klopfenstein said. He knows of a large feedlot where the nutritionist balances rations for .35 phosphorous. "The published (NRC) requirement is .25, and we say it is quite a bit lower. He (the nutritionist) knows our data, but he cannot bring himself to reduce it," Klopfenstein said. Klopfenstein calculated the 120,000-head feedlot spent $400,000 a year on unneeded phosphorous. "Not only is it not necessary, but it is adding to the environmental problem," he said. The amount of nitrogen applied is based on matching nitrogen content to plant needs. Although feedlot manure's nitrogen to phosphorous ratio is typically 2:1, plants use those nutrients in a ratio of 5:1, meaning phosphorous is sometimes over applied. Manure applications are now required to be based only on nitrogen. NU's study started in the mid-1990s in anticipation of stricter government scrutiny on phosphorous; those rules may tighten soon. "Our understanding is that in probably about a year the mandate will require that manure be applied on a phosphorous basis," Klopfenstein said. NRC dietary guidelines, last published in 1996, are based on 1950s research with dairy cattle. "So they are not very applicable to today's conditions, diets and types of cattle," he said. New guidelines will not be published for five to seven years. Although he is not aware of other research on reduced phosphorous in beef cattle, work has been done with dairy cattle. "It shows the same thing; we've been overfeeding," Klopfenstein said. In a related project, Klopfenstein and others at NU are in the planning stages for a demonstration project on how to better distribute manure on farmland. They also hope to increase manure applications in the state. "There are plenty of crop acres to put it on. We buy a lot of commercial fertilizer in Nebraska. It is just a matter of getting the manure distributed back on the land," he said. © |
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