Physical and Metabolic Constraints on Feed Intake in Ruminants: A Systematic Model

Feed intake control in ruminants is mediated through physical and metabolic constraints. Rumen fill, dietary fiber concentration, and fiber digestibility are important physical constraints. Rumen volatile fatty acids (VFA) concentrations, post-rumen nutrient assimilation and absorption, and hepatic and systemic nutrient balance (and imbalance) are important metabolic constraints on feed intake. Blood levels of glucose and some ketones and fatty acids are other significant players in feed intake regulation in ruminants. Research is needed to elucidate how to optimize feeding strategies and feeding systems to improve feed intake in high-producing ruminants.