At the Hanor Company, the “diet library” at every mill includes late-phase rations 65% higher in soybean meal to finishing pigs challenged with inflammatory diseases like mycoplasma, Hemophilus parasuis, porcine reproductive and respiratory syndrome (PRRS) or porcine circovirus-associated disease (PCVAD).

Hanor’s nutrition director, Dean Boyd, addressed protein levels for low-health pigs at the Minnesota Nutrition Conference in Owatonna, MN.

The finding that higher soybean meal levels have a positive effect on sick pigs was something they stumbled upon, Boyd says, and it has profound implications on feed cost of gain.

“It was discovered by accident when pigs in a study were unexpectedly infected with diseases that cause systemic inflammation,” he recalls. “An apparent experimental disaster resulted in a fortuitous outcome with extraordinary financial implications.”

The study’s original objective was to reverify true ileal digestible (TID) lysine requirement for pigs fed 4.5 g/ton of Paylean (Elanco Animal Health) using carcass average daily gain (ADG) and feed conversion ratio (FCR) as the main criteria (Table 1).

“We wanted to verify that a low soybean meal, high crystalline amino acid regimen favored carcass ADG and FCR, because you can get misled using whole body growth,” Boyd explains.

Trial results were contrary to previous work, but pigs were sick during the test. In fact, mortality and morbidity averaged 12.7% for the 16-week finishing period, which was six times higher than normal. Diagnostic tests showed the pigs were PRRS- and PCVAD-positive; Strep suis was also isolated.

“These viruses produce quite an inflammatory effect,” Boyd notes. “Growth plummets and because the pigs don’t eat much different, feed conversion was off the charts. You just get hammered.” Carcass yield is less with persistent inflammatory effects as well.

When pigs are healthy, diets containing crystalline amino acids like lysine with lower soybean meal are still favored to keep costs in check, especially when Paylean is added, he explains. Now, when disease surfaces at the Kentucky-based company, word travels down the pipeline to switch to higher soybean meal diets.

“With 65,000 sows and 1.3 million pigs, Hanor is small compared to some,” Boyd says. But a decision to use synthetic amino acids in diets lowered the number of 24-ton semi-trailer loads of soybean meal per year by 1,500. “It was an impressive downgrade, but we learned that soybean meal, at times, should not be replaced,” he explained.

Whether it’s the anti-inflammatory isoflavones in soybeans that negate effects of inflammation, or a crude protein phenomenon, Boyd is not sure. But he figures inflammatory disease imposes a cost of $1.50 to $3.50/pig.

“It seemed our studies were ruined by disease, but this proved fortuitous, as an important principle for diet formulation in practice was exposed,” he says. “This may be one reason for field reports that use of high crystalline amino acid levels (low protein diets) do not always perform to expectations.”

At Hanor, the challenge is to implement diets that minimize formula cost by maximizing crystalline amino acids when pigs are healthy, but restricting their use when pigs are not.

“We enlarged our diet library for the finishing phase to include diets with traditional crystalline lysine levels (1 to 3 lb./ton), and until we learn otherwise, restricted levels of distiller’s dried grains with solubles (10% maximum) to favor soybean meal level,” Boyd explains.

The order of diets at Hanor is determined for each flow according to whether pigs are being challenged with inflammatory disease. An attempt is made to implement dietary changes slightly ahead of an expected challenge, and once implemented, the diet strategy continues until pigs are marketed.

Boyd believes their work shows for the first time that inflammatory challenges from diseases such as PRRS, PCVAD and mycoplasma require high soybean meal (or low crystalline lysine) levels in order to minimize the substantial loss in whole-body and carcass ADG, and especially FCR.

“Both whole body and carcass criteria responded to elevated soybean meal under disease challenge. We think it’s a sensible thing to do,” he reinforces.