Chronophysiology of ruminant feeding behavior and metabolism: an evolutionary review

Abstract

Circadian rhythms of rumen, splanchnic, and peripheral metabolism may be synchronized with endogenous physiological rhythms to maximize ruminant efficiency. Such synchronies are largely led by circadian rhythms of feeding behavior. Post-feeding intake rhythms are important entities of ruminant feeding behavior. Environmental cues such as feeding timing and photoperiod alter feeding behavior by altering postprandial intake patterns. Feed ingestion and natural grazing have evolved to occur mainly around sunrise, afternoon, and sunset. As such, rumination has evolved to occur when no or little eating occurs or overnight. Manipulating feeding time in modern ruminants alters post-feeding rumen fermentation and peripheral metabolism rhythms. An evolutionary literature review on circadian rhythms of ingestion, rumination, digestion, and metabolism enables integration of the most recent discoveries with science of several past decades to develop insights on improving ruminant nutritional management. These serve as a model for other high-producing livestock and humans. A special descriptive emphasis is placed on how feeding timing affects chain physiological rhythms of ingestion, rumination, rumen fermentation, and portal, splanchnic, and peripheral metabolism. Innovative efforts in improving production efficiency in the twenty-first century will consider ruminant behavior in light of the endogenous physiological rhythms of rumen and host metabolism. This will ensure moving toward optimal rumen and animal physiology and health, farm economics, environmental quality, and safe and secure human food supply.