Improvements in the nutritive value of soybeans and soybean meals by selective breeding

Sarah Cervantes-Pahm¹, Alejandro Buentello², and John Schillinger³

¹Director of Feed Marketing – South East Asia, Schillinger Genetics, Inc.

²VP of Research and Aquaculture Business, Schillinger Genetics, Inc.

³President, Schillinger Genetics, Inc., West Des Moines, IA, USA

Soybeans or soybean meals (SBM), are the major source of protein in livestock diets. Despite the presence of anti-nutritional factors (i.e., trypsin inhibitors [TI] and oligosaccharides) that limit their potential inclusion levels in diets for monogastric animals, soybeans or SBM are one of the best plant protein sources for animal feeds. The removal of anti-nutritional factors in soy products is usually achieved using various processing techniques. However, reducing the concentration of TI and oligosaccharides can also be attained by selective breeding. Recently, Schillinger Genetics has successfully produced novel soybean varieties (Navita™) that contain TI and oligosaccharides at significantly reduced concentrations as compared to those present in conventional soybeans or SBM.

Low TI SBM. Unique soybean cultivars have been developed that contain 65-90% less TI than conventional soybeans. We hypothesize that heat deactivation may not be necessary for these particular varieties of soybean. At the University of Georgia (unpublished data, Batal, 2011), SBM obtained from low and ultra-low TI soybean varieties were cold-pressed, and meals were fed to broiler chickens. The concentration of TI in the low-TI (16,000 TIU/g) and the ultra-low TI SBM (5,000 TIU/g) was less than the concentration of TI in cold-pressed conventional soybeans (46,000 TIU), but was greater than in conventionally-treated SBM (de-hulled, solvent extracted, roasted; 3,100 TIU). True metabolizable energy corrected for nitrogen (TMEn) in the low and ultra-low TI SBM was greater (average 3,749 kcal/kg) than in conventional soybean (3,612 kcal/kg) and conventional SBM (3,000 kcal/kg). The greater TMEn of the SBM obtained from low TI and ultra-low TI soybeans was attributed to the greater concentration of lipids in these meals (7.8-14.1%) compared with the 1.9% lipid concentration in conventional SBM. This indicates that less supplemental oil is needed when cold pressed low TI or ultra-low TI SBM replaces conventional SBM in diets for broilers.

Similar results were obtained in a swine experiment conducted at the University of Illinois, Urbana (unpublished data, Stein et al., 2011). Metabolizable energy of cold pressed low and ultra-low TI soybean (average 4,369 kcal/kg) was also greater than in conventional SBM (4,006 kcal/kg). Standardized ileal amino acid digestibility of Lys, Met, Thr, and Trp in cold pressed low and ultra-low TI soybeans did not differ from their heat processed counterparts, indicating that heat processing of low and ultra-low TI soybeans was not necessary for optimal AA digestibility of these novel soybeans.

Low oligosaccharide SBM. Soybean meal obtained from low oligosaccharide soybean varieties contained 91% less oligosaccharides (stachyose and raffinose) than conventional SBM. In a recent experiment conducted at Auburn University (unpublished data, Dozier et al., 2010), SBM derived from low-oligosaccharide and high crude protein (CP) soybean varieties were incorporated in diets and fed to broiler chickens. Apparent metabolizable energy values corrected for nitrogen (AMEn) were 7% higher for birds fed low-oligosaccharide-high CP SBM (53% CP and 1.7 % oligosaccharide; AMEn 2,360 kcal/kg) compared with birds fed conventional SBM (46.6% CP and 7.3% oligosaccharide; AMEn 2,190 kcal/kg). Growth studies conducted with these same meals indicated that 13 day-old chicks fed the low oligosaccharide-high-CP SBM attained an 18 g advantage in body weight compared with birds fed conventional SBM (381 g versus 363 g). Feed conversion ratio and body weight at 40 days were not different between birds fed the low-oligosaccharide-high-CP SBM and conventional SBM, but 17% less SBM was required in low-oligosaccharide-high-CP diets to meet the chicken’s CP and amino acid requirement.

From a practical perspective, the value added advantage in using these novel soybean varieties is highlighted by savings in processing costs (no need for heat-deactivation of protease inhibitors), absence of nutrient deterioration associated with heating, and the elimination of detrimental effects of oligosaccharides in novel soybean varieties developed at Schillinger Genetics.