University of Illinois research shows that fermented soybean meal can replace fish meal in diets fed to weanling pigs, thus reducing diet costs.

Because protein from soybean meal contains anti-nutritional compounds that decrease nutrient availability and reduce growth performance of weanling pigs, inclusion of soybean meal is usually restricted in weaned pig diets. Fish meal is often used in these diets to furnish the amino acids that pigs need.

However, the cost of fish meal has increased dramatically during the last few years, making it necessary to find alternative protein sources.

Fermentation of soybean meal removes many of the anti-nutritional factors and is now being produced in the United States. But no information is available about the digestibility of nutrients in U.S.-produced, fermented soybean meal.

This research was conducted to determine the digestibility of phosphorus and amino acids in fermented soybean meal fed to weanling pigs.

Two experiments were conducted, both using PepSoyGen by Nutra Ferma, Sioux City, IA (www.nutraferma.com); it is produced by fermentation of soybean meal in the presence of Aspergillus oryzae and Lactobacillus subtilis. Conventional soybean meal and menhaden fish meal were also included in the amino acid digestibility experiment.

Experiment 1 determined the apparent and standardized total tract digestibility (ATTD and STTD, respectively) of phosphorus in fermented soybean meal and in conventional soybean meal. Four corn starch-soybean meal diets were formulated by using either fermented or conventional soybean meal with phytase (OptiPhos, Enzyvia, LLC, Sheridan, IN) or without phytase. A phosphorus-free diet was also included to measure phosphorus losses.

Thirty weaned barrows weighing 31 lb. were fed the five diets with six replicates per diet. Feces were collected for five days after a five-day adaptation period. Diets and feces were analyzed for phosphorus, and the values for ATTD and STTD in each of the diets containing soybean meal were calculated.

Experiment 2 measured the standardized ileal digestibility (SID) of amino acids in fermented soybean meal, conventional soybean meal and fish meal. Three diets were formulated to contain each of these ingredients as the sole source of amino acids. A nitrogen-free control diet measured ileal losses of amino acids.

Eight weaned barrows weighing 23 lb. were equipped with a T-cannula in the distal ileum, and ileal digesta were collected from each pig for two days after a five-day adaptation period. Each pig was fed each diet so there were eight observations per diet. All digesta samples were analyzed for amino acids, and the SID of amino acids in fermented soybean meal, conventional soybean meal and fish meal were calculated.

Results of Experiment 1 indicated that the concentration of phosphorus in feces and the daily phosphorus output decreased when phytase was fed, and phosphorus concentration in feces and daily phosphorus output were less in pigs fed fermented soybean meal than in pigs fed conventional soybean meal (Table 1).

The ATTD and STTD of phosphorus were greater in fermented soybean meal than in conventional soybean meal if no phytase was included in the diets. But if phytase was used, the difference between the two sources of soybean meal was less, meaning that fermentation releases some of the phosphorus bound in the phytate in soybean meal, which increases the digestibility of phosphorus in fermented soybean meal vs. conventional soybean meal.

Results of Experiment 2 indicate that the SID of most amino acids is greater in fermented soybean meal than in fish meal, and for methionine and valine, the SID in fermented soybean meal is also greater than in conventional soybean meal (Table 2).

There were no differences in SID values for all other amino acids between the two sources of soybean meal. This suggests that amino acids in fermented soybean meal are easily digested by young pigs.

The results of the two experiments indicate that fermented soybean meal is an excellent source of digestible phosphorus and digestible amino acids. Therefore, it is likely that the source of fermented soybean meal used in these experiments can replace fish meal in diets fed to weaned pigs, possibly reducing diet costs.

Researchers: O.J. Rojas and H.H. Stein, University of Illinois. For more information, contact Stein by phone (217) 333-0013, fax (217) 333-7088 or e-mail hstein@uiuc.edu.