Soybean meal contains anti-nutritional factors, such as oligosaccharides and antigens, that restrict its use in diets fed to weanling pigs.

Fermentation of soybean meal eliminates some of these antinutritional factors, making fermented soybean meal a potential lower-cost substitute for animal protein in starter diets. Soybean meal fermented in the presence of Aspergillus oryzae and Lactobacillus subtilis has recently become available on the United States market. To aid in the formulation of diets containing fermented soybean meal, researchers at the University of Illinois have determined the digestibility of energy and amino acids in this ingredient.

"Fermented soybean meal contains fewer antinutritional factors and is well tolerated by weanling pigs," said Hans Stein, professor of animal sciences. "But there is a lack of data on the digestibility of energy and amino acids. So our goal was to determine those values."

Professor Stein's lab conducted two experiments. In the first, they determined the concentration of digestible, metabolisable and net energy in fermented soybean meal. In the second, they determined the standardised ileal digestibility of crude protein and amino acids. Both studies included conventional soybean meal and fish meal for comparison.

On a dry matter basis, fermented soybean meal contained 4,296kcal per kg digestible energy (DE), 3,781kcal per kg metabolisable energy (ME), and 2,710kcal per kg net energy (NE). These values compared favourably to those in fish meal, which contained 3,827kcal per kg DE, 3,412kcal per kg ME and 2,450kcal per kg NE. DE, ME and NE were decreased in fermented soybean meal compared with conventional soybean meal, which contained DE, ME and NE of 4,553kcal per kg, 4,137kcal per kg, and 2,972kcal per kg, respectively.

Professor Stein explained: "Fermentation of soybean meal removes sugars and oligosaccharides. Sucrose is easily digested by pigs and oligosaccharides are almost completely fermented. When these are removed, the remaining meal contains a greater percentage of fibre, which reduces the digestibility of energy in the diets."

Digestibility of crude protein and amino acids in fermented soybean meal was the same as or greater than that of soybean meal. Digestibility values for most amino acids were greater in fermented soybean meal than in fish meal.

Professor Stein said the results indicated that fermented soybean meal could replace fish meal in starter diets without negatively affecting the energy content or digestible amino acid content of the diets.

"With this new product on the market in the United States, producers have another option for providing protein in weanling pig diets," he said.

The study, entitled 'Concentration of digestible, metabolizable, and net energy and digestibility of energy and nutrients in fermented soybean meal, conventional soybean meal, and fish meal fed to weanling pigs', was recently published in the Journal of Animal Science and was co-authored with Oscar Rojas, a PhD candidate in the Stein Monogastric Nutrition Laboratory at Illinois. It is available online [click here].

November 2013