“We wanted to determine the energy concentration and digestibility of phosphorus in whey powder, conventional whey permeate and in low-ash whey permeate because these values had not been determined,” says Hans Stein, University of Illinois swine nutritionist. Researchers specifically evaluated these options for weaned-pig diets.

Skim milk powder has been used to meet weaned pigs’ lactose requirement, but it’s a costly option. Whey powder, a co-product of the cheese industry, contains lactose and protein and is more economical to use in pig diets, Stein says.

“Some companies take the protein out of whey powder because they sell it for the human food market,” he explains. “That leaves them with whey permeate, which contains mainly lactose and ash.”

The study looked at conventional whey powder, which is 66 percent lactose, 13.2 percent crude protein and 15.8 percent ash. Two permeate products also were considered. One was a conventional whey permeate that contained about 76 percent lactose and 9 percent ash. The other product has most of the ash removed — it had only 1.7 percent ash and approximately 89 percent lactose.

The metabolizable energy concentration and the standardized total tract digestibility of phosphorus were determined. Results show that the conventional whey permeate contains less metabolizable energy than whey powder (3,081 versus 3,462 kcal per kg dry matter). However, the low-ash whey permeate contained 3,593 kcal metabolizable energy per kg dry matter.

Removing protein from whey powder reduced the metabolizable energy concentration in the whey permeate. If ash also is removed, the resulting high-lactose, low-ash whey permeate has a metabolizable energy concentration that is slightly greater than in whey powder, Stein notes.

The concentration of phosphorus in whey powder, conventional whey permeate and low-ash whey permeate was 0.63 percent, 0.57 percent and 0.10 percent, respectively, but the standardized total tract digestibility of phosphorus was not different among the three ingredients (91.2 percent, 93.1 percent and 91.8 percent, respectively).

“These data clearly indicate that phosphorus from all three ingredients is well digested by weanling pigs,” he says.

Consequently, it’s possible to include whey powder, whey permeate or low-ash whey permeate in weaned-pig diets that are formulated on the basis of metabolizable energy and the standardized total tract digestibility of phosphorus.

“These data will provide the feed industry and swine producers with more options to include lactose in the diets,” Stein says.