TECHNOLOGY FEED & ADDITIVE MAGAZINE September 2025 61 WHY IN VITRO METHODS MATTER Traditionally, diet formulation has relied on in vivo trials to determine digestible and metabolizable energy. These trials are accurate but slow, costly, and raise ethical concerns. Existing in vitro systems, meanwhile, are often too simplistic or poorly standardized to replace live-animal trials. Simulated Digestion System (SDS III) changes this. Developed over more than a decade of research, it uses computer-controlled digestion to simulate the full gastrointestinal tract of pigs and poultry. By integrating automation, absorption simulation, and validated prediction equations, SDS III provides fast, reliable, and cost-effective results that closely match in vivo outcomes. For nutritionists and feed mills, the benefits are clear: • High throughput: Dozens of samples tested within days, versus months for animal trials. • Cost efficiency: Reduced reliance on expensive facilities and animal care. • Deeper insights: Enables study of nutrient release and digestion dynamics not easily observed in animals. • Ethical advantages: Supports the 3Rs principle (Replacement, Reduction, Refinement). THE SHORTCOMINGS OF CONVENTIONAL IN VITRO METHODS Despite their promise, most in vitro systems face several issues: • No simulation of absorption, leading to incomplete energy predictions. • Technical artifacts, such as digesta sticking to plasticware, evaporation during incubation, and inaccurate pH adjustments. • Operator variability due to manual pH and enzyme additions. • Inconsistent enzyme activity across different commercial batches. In modern livestock production, feed accounts for around 70% of total production costs. Among these expenses, energy sources contribute up to 50% and protein ingredients up to 40%. Getting these values right is critical for precision livestock feeding. Overestimating feed energy or protein digestibility risks underfeeding animals and reducing growth performance, while underestimating inflates costs by driving unnecessary supplementation. Precision is not only about economics— it is also about sustainability, since inefficient feed use increases nitrogen excretion and greenhouse gas emissions. This is where the Simulated Digestion System (SDS III) offers a new path forward. SDS III for In Vitro Feed Digestibility: A GAME-CHANGER FOR FEED MILLS Dr. Shukun Yu Senior Consultant UniVOOK Chemical
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