Last year, when monocalcium phosphate (monocal) and dicalcium phosphate (dical) were fetching $1,000/ton, University of Illinois (UI) swine nutritionist Hans Stein received several calls from pork producers and feed company nutritionists seeking advice on lowering phosphorus levels in swine diets.
“I told them if they used phytase and DDGS (dried distiller's grains with solubles)  they could probably take supplemental phosphorus down a lot,” Stein remembers.
But formal research to back his recommendation was lacking, so Stein was left a bit uneasy. “We had looked at the phosphorus digestibility of DDGS and the effect of phytase, but we had never looked at them together,” he explains. “I wanted to make sure it worked like I thought it would.”
Stein and graduate student Ferdinando Almeida recently completed a study that proved his theory. They demonstrated that inorganic phosphorus (dical or monocal) can be eliminated altogether in nursery diets when phytase and DDGS are used in tandem.
“You can increase the absorption rate or digestibility of phosphorus by 20 to 40%, even if you reduce the inclusion rate of dical in the diet,” Stein says. The exact increase in digestibility depends on whether you use just DDGS or DDGS with phytase, he adds.
The project, conducted last winter at UI's swine research farm, studied four diets listed in Table 1 , including:
Traditional corn-soybean meal diet (control diet);
Traditional corn-soybean meal diet with phytase (500 FTU/kg);
Corn-soybean meal diet with 20% DDGS; and
Corn-soybean meal diet with 20% DDGS and phytase (500 FTU/kg or 227 FTU/lb.).
Pigs were started on study diets at 24.2 lb. and fed for three weeks. Researchers measured average daily gain (ADG), average daily feed intake (ADFI), feed conversion rate (FCR) and obtained urine and fecal samples from pigs on all four diets to assess phosphorus excretion. They calculated the digestibility of phosphorus based on phosphorus fed vs. phosphorus excreted in manure or urine. Each feeding regimen was repeated 10 times.
Digestibility Bumped 50%
Normally, about a third of the phosphorus in corn or soybean meal is available to a pig. The rest is bound in a non-absorbable structure called phytate, Stein explains.
“Everything that is not absorbed goes out in manure; it just passes through the pig and that's why we have a lot of phosphorus in the manure,” Stein says.
The Illinois researchers also saw a “dramatic increase” in the digestibility of phosphorus in the pigs receiving the diet containing DDGS and phytase vs. those on the traditional corn and soybean meal diets. They calculated phosphorus excretion at 1.68 grams/pig/day for the control diet.
When 20% DDGS was included in the diet, phosphorus excretion dropped to 1.43 g/day. The addition of phytase dropped excretion levels to 0.82 g/day.
No Added Dical
Pigs received 1.15% dical for the control diet, 0.35% dical for the corn-soybean meal diet with phytase, and 0.65% dical for the corn-soybean meal diet with 20% DDGS. No added dical was used in the diet containing 20% DDGS and phytase.
Performance of the pigs remained constant, even in the diets where dical was eliminated. ADG was 1.12 lb./day for the control diet and 1.13 lb/day for the diet with DDGS and phytase. Feed efficiency was 1.51 for the control diet and 1.56 for the diet containing DDGS and phytase.
“Basically, we cut excretion of phosphorus in half and used no added inorganic phosphorus and performance of the pigs was exactly the same,” says Stein.
“If you can do it with younger pigs, you can certainly do it for older pigs,” he predicts. “The phosphorus requirement goes down as they get older. Sows could be a little different because their requirements are higher, but for growing and finishing pigs we are very confident you can feed them without any dical,” Stein summarizes.
Nutritionist Leann McGinnis of J and R Distributing in Lake Norden, SD, cut monocal levels by up to 0.5% in grow-finish rations last year when clients were looking for dietary cost-savings.
“We increased phytase from 500 to 750 units and increased DDGS levels, but we never took all of the monocal out because there was nothing out there that gave us confidence we could do that,” she says.
McGinnis says that once monocal prices dropped to earlier levels, some of her clients returned to traditional diets with higher levels of inorganic phosphorus. “Some clients weren't satisfied with their performance (on the new diet), but others have kept the same diet (with lower monocal rates),” she says.