E: 92 Soy as a Feed Ingredient and Protein Info You Need to Hear

Send Audrey a Text to get your question answered on the showRecently there was some push back around soy as an ingredient and more over as an amino acid requirement in feed and or ration balancers. The good ol “show me the scientific evidence” came right out. So lets talk about soy as an ingredient and why it matters even for horses that don’t have a direct sensitivity or allergy for soy. Today we will talk through a few different aspects including soys anti-nutrient properties, glyphosate issues, and the all important “what about amino acids then?”  SourcesLysine as the first limiting amino acid in horsesNational Research Council (NRC). (2007). Nutrient Requirements of Horses (6th rev. ed.). Washington, DC: National Academies Press. Establishes lysine as the first limiting amino acid in typical equine diets and emphasizes amino acid balance over crude protein.Lysine, threonine, and methionine requirements and ratiosMansilla, W. D., et al. (2020). Amino acid requirements in horses: Current knowledge and future perspectives. Animals, 10(4), 682. https://doi.org/10.3390/ani10040682Reviews essential amino acid requirements in horses; discusses lysine as first limiting, with threonine and methionine following depending on diet.Threonine as a secondary limiting amino acidHarris, P. A., & Pagan, J. D. (1999). Protein and amino acid nutrition in the performance horse. Proceedings of the Equine Nutrition Conference, Kentucky Equine Research.Discusses lysine as first limiting and identifies threonine as potentially limiting when lysine is corrected.Functional importance of lysine and threonine (equine studies)Zhang, L., et al. (2023). Effects of lysine and threonine supplementation on milk yield, amino acid metabolism, and fecal microbiota of lactating mares. Journal of Animal Science and Biotechnology, 14, 84. https://doi.org/10.1186/s40104-023-00884-5Demonstrates physiological and metabolic effects of lysine and threonine supplementation in horses.Balanced amino acid profiles vs crude proteinGraham-Thiers, P. M., & Kronfeld, D. S. (2005). Amino acid supplementation improves muscle mass in exercising horses fed diets adequate in crude protein. Journal of Nutrition, 135(9), 2144–2148. https://doi.org/10.1093/jn/135.9.2144Shows that horses fed “adequate” crude protein still benefit from targeted amino acid supplementation.Ideal protein concept (amino acid balance over quantity)Wu, G. (2014). Dietary requirements of synthesizable amino acids by animals: A paradigm shift in protein nutrition. Journal of Animal Science and Biotechnology, 5, 34. https://doi.org/10.1186/2049-1891-5-34Introduces and supports the concept that amino acid balance determines protein utilization more than total protein intake.Why crude protein is a poor metricCrude protein vs usable proteinMillward, D. J., et al. (2008). Protein quality assessment: Impact of digestibility and amino acid composition. British Journal of Nutrition, 99(5), 995–1011. https://doi.org/10.1017/S0007114507868495Explains why nitrogen-based protein estimates do not reflect biological protein value.Amino acid digestibility and bioavailabilityGilani, G. S., et al. (2012). Protein quality evaluation: Impact of digestibility and amino acid availability. Journal of AOAC International, 95(5), 1398–1411. https://doi.org/10.5740/jaoacint.11-028Demonstrates that digestibility and amino acid profile determine usable protein, not crude protein.Conditionally essential amino acids (rate-limiting functions)Wu, G., et al. (2013). Amino acids: metabolism, Minerals and Metals Mane Test: https://equine-energy-medicine.myshopify.com/products/minerals-and-metals-mane-test?variant=66748496150832Find all the resources listed here: linktr.ee/equineenergymedAudrey is not an MD or DVM and has never implied or claimed to be either. Audrey holds a Doctoral Degree in Traditional Naturopathy and a Master's Degree in Science. She created an evidence-based anti-inflammatory nutrition program for equines and has successfully helped over 10k horses with a balanced anti-inflammatory forage diet. This information is non-medical in nature and is not meant to diagnose, prescribe for, treat, or cure, and is not a replacement for your veterinarian.  These are my personal interpretations based on my education, skills, and experience. Equine Energy Medicine refers to non-invasive, supportive modalities focused on energetic balance, nutrition, and overall well-being, and does not replace veterinary care.