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Timing of feed presentation entrains periprandial rhythms of energy metabolism indicators in once-daily fed lactating cows

The nature of feeding time-driven rhythms in animal and human physiology requires mechanistic exploration. The objective was to establish effects of feeding time of diets with different forage to concentrate ratios on periprandial rhythms and daily averages of peripheral non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHBA) as indicator of energy metabolism. Eight early-mid lactation Holsteins including four multiparous and four primiparous cows were utilized in a 4 × 4 Latin square design study with a 2 × 2 factorial arrangement of feeding time and diet type. A higher concentrate (HC, forage to concentrate ratio = 38.5:61.5) or a lower concentrate (LC, forage to concentrate ratio = 50.6:49.4) total mixed ration (TMR) was presented at either 21:00 h or 09:00 h. The study had four 21-d periods, with 14 d of adaptation. Peripheral blood was sampled every 2 h for two non-consecutive 24-h periods. Feeding at 21:00 h vs. 09:00 h increased feed intake within 3 h post-feeding from 26% to 37% of total daily intake, and improved milk energy yield without affecting total daily dry matter intake. Peripheral blood BHBA in both parities and NEFA in multiparous cows exhibited significant periprandial rhythms. Peripheral BHBA was higher at 2 h and 4 h post-feeding in cows fed at 21:00 h vs. 09:00 h. The HC vs. LC diet decreased daily means of blood BHBA. Primiparous cows had higher average daily blood NEFA than multiparous cows. Data substantiate that evening instead of morning feeding increased eating rate and feed intake shortly post-feeding and, thereby, altered periprandial rhythms of peripheral energy and fat metabolism indictors. Feeding time, therefore, is established to entrain peripheral energy-yielding substrate availability and use in lactating cows. As optimal understanding of splanhnic and peripheral metabolism in a given species depends on the comparative nature of animal–human chronophysiology, the study serves as a metabolic model for high-producing livestock and human.