Review: Ruminant feed intake regulation evolution: chronophysiological rhythms perspectives

Abstract

Mechanistic and rhythmic understanding of feed intake regulation is required for accurate intake prediction and estimation of intake effects on ruminant production and health. The objective was to review new evolutionary insights into ruminant feed intake regulation from chronophysiological rhythms perspectives. Various dietary, animal, and chronoenvironmental factors as well as housing, grouping, and feeding management strategies affect ruminant feed intake. Natural circadian rhythms of grazing and rumination lead to innovative approaches for accurate predictions of specific nutrient intake under intensive systems of production. Ruminants have evolved to ruminate mostly overnight and graze during day, especially around sunrise and sunset. As such, rumen fermentation, post-rumen nutrient assimilation, and peripheral metabolism possess circadian rhythms. These evolutionary rhythms in feeding behavior and metabolism have led to specialized annual, seasonal, and circadian rhythms in ruminant endocrinology. Most recent findings compellingly advocate alterations in post-feeding intake rhythms of non-grazing lactating cows by altering feed delivery timing. These findings establish the chronological nature of feed intake regulation in postmodern ruminants. Timing of feeding as a major external cue affects how rapidly, extensively, and efficiently feed ingestion, rumination, fermentation, and metabolism occur. These chronological evolutionary perspectives should be quantified and incorporated into current feed intake control models for improved prediction accuracy and precision. The current knowledge and insights suggest that evening feeding offers advantages to optimize circadian rhythms of dry matter intake and ruminant production efficiency.