Timing of eating a global orchestrator of biological rhythms: dairy cow nitrogen metabolism and milk fatty acids

Abstract

Timing of eating is a multiscience biological rhythms discipline that orchestrates global animal and human chronophysiology and metabolism. The objective of this study was to establish biological rhythmic effects of providing a total mixed ration (TMR) at either 0900 h or 2100 h on rumen microbial protein biomass, nitrogen partitioning, and milk fatty acids in a lactating dairy cow model. Four multiparous and four primiparous Holstein cows were monitored in a cross-over design study with two 42-day periods. Each period consisted of 21-day adaptation and 21-day sampling and data collection. The TMR had a forage:concentrate ratio of 50.2:49.8 (dry matter based). Total urine and feces were collected during a sampling week in each period to measure nitrogen partitioning. Urinary excretion of purine derivatives was utilized to estimate microbial protein biomass. Provision of TMR at 2100 h vs. 0900 h increased nitrogen intake and milk yields of total fats and health-improving anti-cancer conjugated linoleic acids (CLA). Evening eating maintained normal rumen function and health as reflected in maintained microbial protein synthesis and milk proportions of total short, medium, and long chain fatty acids. Feeding at 2100 h instead of 0900 h decreased milk proportions of C_10:0, C_12:0, C_12:1, C_13:0, C_13:1, and C_{18:3 n-3}, and tended to decrease proportions of C_8:0 and C_{18:1 trans-9}, while increasing that of C_18:0. Evening instead of morning eating reduced the proportion of nitrogen that was excreted via urine and feces and secreted in milk. Findings suggest that feed delivery at 2100 h vs. 0900 h improved nitrogen dynamics and metabolism. Reduced N excretion and increased milk yields of total fats and health-improving fatty acids (e.g. CLA) by evening eating possess environmental and life quality implications.

Keywords:

• chronophysiology
• dairy cow
• microbial protein
• milk fatty acid
• rhythm

Acknowledgements

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