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ARS Home » Southeast Area » Stoneville, Mississippi » Crop Genetics Research » Research » Publications at this Location » Publication #329166
Title: A survey of the agronomic and end-use characteristics of low phytic acid soybeans

Author
item AVERITT, BEN - Virginia Tech
item ZHANG, BO - Virginia Tech
item Li, Shuxian
item CHEN, PENGYIN - University Of Arkansas

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 6/3/2016
Publication Date: 1/6/2017
Citation: Averitt, B., Zhang, B., Li, S., Chen, P. 2017. A survey of the agronomic and end-use characteristics of low phytic acid soybeans. In: Fletcher, B., editor. Soybeans: Cultivation, Nutritional Properties and Effects on Health. Hauppauge, NY: Nova Science Publishers, Inc. p. 21-33.

Interpretive Summary: Soybean is one of the most widely grown agronomic crops in the United States. Around 98% of those soybeans are used in animal feeds ranging from swine and cattle to domestic animals and aquaculture. Approximately 75% of the phosphorus in soybean is in the form of phytic acid (PA). However, PA is indigestible by nonruminant livestock and is considered an anti-nutritional factor in soybean meal. This chapter will introduce phytic acid and low phytic acid (LPA) soybeans, which has shown an exciting possibility for increasing the efficiency and reducing the cost of animal feeds, while also serving to protect our natural resources and preserve our waterways. More research is still needed to improve field emergence of LPA soybeans and to explore the possibilities of using LPA soymeal-based feeds in other markets such as aquaculture, the prospect of which is beneficial to both soybean production and the aquaculture market.

Technical Abstract: With unique high protein and oil contents, soybean (Glycine max L. merr.) is one of the most widely grown agronomic crops in the United States. Around 98% of those soybeans are used in animal feeds ranging from swine and cattle to domestic animals and aquaculture. This chapter will introduce phytic acid, an antinutritional factor in soybean seeds, soybean meal and phytic acid in animal production, low phytic acid (LPA) soybeans, LPA soybean in meal production and the potential problems of LPA soybeans. Around 75% of the phosphorus in soybeans is in the form of phytic acid, myo-inositol-1,2,3,4,5,6-hexakisphosphate, or phytate, the mixed cation salt thereof. This presents major nutritional and environmental issues as mono- and agastric animals such as swine, poultry, and fish lack the activity of a phytase enzyme in their digestive track and, thus cannot digest and utilize the majority of the P in soymeal. Further, phytic acid acts as a chelator binding various vitamins and minerals and thus making them unavailable to the animal. The undigested phytic acid is deposited in the animal waste where it can wash into bodies of water where natural phytase enzymes can digest it to bioavailable inorganic P. This, in turn, leads to environmental damage through nutrient pollution leading to algal blooms and hypoxia, a lack of dissolved oxygen in the water which can result in massive fish death. To counteract this, plant breeders have developed low phytic acid (LPA) soybean varieties using three distinct mutant alleles, lpa1, lpa2, and MIPS1. LPA soybean varieties contain up to 75% less phytic acid and 75% more inorganic P than normal phytic acid varieties. Varieties with the MIPS1 mutant allele also exhibit a more beneficial sugar profile high in easily digestible sucrose and low in less digestible raffinose and stachyose. Use of these LPA varieties as feedstuffs for swine and poultry has shown decreased P in the animal waste as well as increased absorbance of P by the animals. Though breeding varieties for phytic acid content has been successful, problems exist to the commercialization of these lines, namely significantly diminished field emergence. Numerous explanations for this phenomenon have been posited including seed source environment, soil borne pathogen pressure, and decreased seedling vigor. Notably, several studies have shown that phytic acid content and emergence are not strongly correlated. Research into overcoming this problem is ongoing.