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| BY GORD LEATHERS Phosphorus in pig manure is a major environmental issue and barley breeders may have come up with an affordable solution. In the past we've tinkered with manure management, we've tin- kered with feed additives and we've even tinkered with the genetics of the pig itself. Duane Falk at the University of Guelph and Brian Rossnagel at the Crop Development Centre in Saskatoon are tinkering with the barley and have come up with a low-phytate, hulless breed that will make a cheap, clean and efficient feed. "The reason to work on low- phytate barley is that all cereal grains have phosphorus in them and that phosphorus is tied up in a form called phytate," Rossnagel said. "The bad news on that is that the phosphorus that's tied up in phytate is not available to an ani- mal such as a pig, or a human for that matter." With cattle this is not an issue because their four-chambered stomachs house bacteria that break it down so the animal can absorb the phosphorus. With pigs, people and poultry the sin- gle-chambered stomach can only move it through. What goes in the front tends to come out the back. This releases the phospho- rus into the environment and leads to considerable controversy regarding phosphorus contami- nation of lakes, streams and groundwater. Phytate is the core of the prob- lem. It's a highly reactive six-car- bon molecule bound to phospho- rus. It lurks within the chemistry of cereals and, once eaten by the pig, it stays intact, holding the much-needed phosphorus within itself in a form the pigs can't digest. To make matters worse, as it moves through the gut of the pig it attracts other minerals and ties them up too. "It also collects the calcium, the potassium, the iron, the zinc and |
the manganese so it's tied up either directly or indirectly," Falk said. "They're actually captured by it and taken on through the animal." These minerals go right through the animal and wind up being dis- carded in manure. In the past the solution was to add minerals to the feed and overdose the pig. Any minerals that didn't get on the phytate express were then avail- able for growth and weight gain. "When swine producers and nutritionists develop feeding rations for pigs they actually have to add calcium phosphate to the diet in order to make sure there's enough available phosphorus for efficient production in the pig barn," Rossnagel said. "The animal gets the mineral it needs but the phytate carries most of the mineral right on through the pig right out into the manure," Falk added. That's why pig manure is rich in phosphorus as well as certain other minerals. Although pig manure, if managed properly, can be an effective fertilizer, it has led to some serious environmental problems with the excess getting into watercourses and causing major spikes in algae growth. Although there's a lot of debate about the source of excess phos- phorus, the hog industry has been fingered as a major contributor. At the very least, more efficient use of minerals in the pig's diet leads to better growth and weight gain and reduced costs in terms of mineral supplements. In light of this Dr. Victor Raboy of the USDA in Aberdeen, Idaho bred a low-phy- tate barley from the Harrington line, and this serves a couple of advantages in terms of feeding. "You don't have to add any more minerals because the pig can get what's in the barley so it's cut- ting down the cost of mineral sup- plementation and it's reducing the |
effect of pig manure on the envi- ronment," Falk said. "And not only that, it's better for the pig because a lot of these supplemented min- erals come in an acid form or some other compound, a salt form which isn't really good for the pig itself either." A low-phytate barley solves the problem of mineral absorption, but there was a second and equally vex- ing problem with the amount of energy the pig can extract, The hulls around the seeds get in the way. "They're cellulose, and pigs are not ruminants," Falk said. "That insoluble fibre is good for you, but only in small amounts, so the energy value of barley is lower than that of corn because it's affected by the hull." The next step was to breed a low-phytate barley with no hull, and in this way it really becomes an efficient feed. Barley is also rel- atively cheap to grow and, with fuel costs going up and nitrogen fertilizer getting more expensive, an efficient feed barley would be a very attractive alternative to corn and soybeans. "It's more digestible and when you take the hull off it not only increases the energy level, it also increases the protein level," Falk said. "The problem with corn is that the protein is pretty low because it's been selected for yield at the expense of protein. A hulless barley has considerably higher protein level than corn and so you need a lot less soybean supple- mentation." Barley growers and hog farmers should be seeing commercial pro- duction starting in the next few years. Rossnagel hopes to get reg- istration next February and would like to see full production by 2009. "At the end of the day it has to get into real producers' hands with real barns with real practical applications before we can deter- mine the total value of the mate- rial," he said. |