Eating timing an evolutionary manager of postmodern rumen physiology and health: a review

Akbar Nikkhah
Department of Animal Sciences, Faculty of Agricultural Sciences, University of Zanjan, Zanjan, Iran

Abstract: Natural diurnal patterns of grazing and rumination lead intensive ruminant production. Ruminants have evolved to ruminate mostly overnight and to graze during the day, especially during sunrise, the afternoon, and sunset. Accordingly, rumen fermentation, postrumen nutrient assimilation, and peripheral metabolism possess circadian patterns. The evolutionary patterns of eating behavior and metabolism have coexisted with seasonal and circadian rhythms in animal endocrinology. Such evolutionary natural eating, ruminating, and rumen fermentation patterns have been facing remarkable improvements in milk and beef production in the last few decades. As a result, new adaptations in ruminant endocrinology and metabolism have occurred. For optimum nutrient use and rumen health, a balanced synchrony between external cues and ruminant internal physiology may be secured. Most recent discoveries suggest that in addition to feed type and amount consumed, eating timing affects postprandial intake and rumen fermentation patterns. Findings of grazing and intensively managed cows are consistent. A main discovery has been an increased eating rate in lactating dairy cows when mixed rations were presented in the evening instead of in the morning. Consequently, evening eating increased rumen volume and fermentation as well as peripheral nutrient supply shortly after feeding. New findings reveal and establish a chronoecological nature for physical and biochemical regulation of feed intake and rumen fermentation. Such quantitative insights can improve the accuracy of rumen metabolism predictions. Eating time will therefore be incorporated into postmodern nutritional programs to ensure optimal rumen function and health. Eating time will be an interface of ruminant evolution, rumen ecology, and modern ruminant farming.

Keywords: eating timing, evolution, health, nutrition, physiology, rumen