Here are some of his major works:
* The Principles of Animal Nutrition (1889) - This book was considered groundbreaking in its time and was widely used as a textbook for many years. It provided a comprehensive overview of the science of animal nutrition, covering topics such as the composition of feeds, digestion, metabolism, and the role of different nutrients in animal health.
* The Nutrition of Farm Animals (1917) - This book was a more advanced treatment of animal nutrition than his earlier work, and it focused on the specific nutritional needs of different farm animals. It is considered a classic work in the field of animal nutrition.
* The Conservation of Energy in Animal Nutrition (1903) - This work explored the concept of energy conservation in animals, including the factors that affect energy expenditure and how this expenditure can be minimized. This research laid the foundation for the Armsby-Woodward System.
* The Armsby-Woodward System - This system for measuring animal feed energy was developed by Armsby and his colleague, John Woodward, at the Pennsylvania State College. It was based on the principle of energy conservation, and it used a series of equations to calculate the amount of energy that an animal could obtain from different feeds. This system allowed for a more accurate assessment of the nutritional value of feeds, which led to improved feeding practices for farm animals.
Besides these major works, Armsby also published numerous research articles and reports on animal nutrition and related topics. He was a prolific writer and speaker, and he played a leading role in the development of the field of animal nutrition in the late 19th and early 20th centuries.