Effects of the timing of protein infusion on the daily rhythms of milk synthesis and plasma hormones and metabolites in dairy cows

Isaac J. Salfer, Cesar I. Matamoros, P. A. Bartell, Kevin J. Harvatine

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Milk synthesis exhibits a daily rhythm that is modified by the timing of feed intake. However, it is unknown how specific nutrients entrain this daily rhythm. Amino acids have an important role in milk synthesis, and may have a role in entrainment of mammary circadian rhythms. The objective of this study was to determine the effects of intestinally absorbed protein on daily rhythms of milk and milk component synthesis and key plasma hormones and metabolites. Nine lactating Holstein cows were assigned to 1 of 3 treatment sequences in a 3 × 3 Latin square. Treatments included abomasal infusions of 500 g/d of sodium caseinate either continuously throughout the day (CON), for 8 h/d from 0900 to 1700 h (DAY), or for 8 h/d from 2100 to 0500 h (NGT). Cows were milked every 6 h during the final 8 d of each period. A 24-h rhythm was fit to data using cosine analysis and the amplitude and acrophase were determined. Night infusion of protein decreased the daily milk yield and milk protein yield by 8.2% and 9.2%, respectively. Milk fat yield was increased 5.5% by DAY and milk fat concentration was increased 8.8% by NGT. Milk yield exhibited a daily rhythm in all treatments, with NGT increasing the amplitude of the daily rhythm 33% compared with CON. Milk fat concentration fit a daily rhythm in CON and NGT, but not DAY, whereas milk protein concentration fit a daily rhythm in CON and DAY, but not NGT. Moreover, DAY abolished the daily rhythm of plasma glucose concentration, but induced rhythms of plasma insulin and nonesterified fatty acid concentrations. Results suggest that feeding increased protein levels during the early part of the day may increase milk fat yield and modify energy metabolism through increased daily variation in insulin-stimulated lipid release, but additional research focused on feeding multiple diets across the day is required.

Original languageEnglish (US)
Pages (from-to)5351-5363
Number of pages13
JournalJournal of Dairy Science
Issue number8
StatePublished - Aug 2023
Externally publishedYes

Bibliographical note

Funding Information:
This research was supported in part by USDA (Kansas City, MO) Agriculture and Food Research Initiative Competitive Grant no. 2015-67015-23358 from the USDA National Institute of Food and Agriculture (PI KJH), National Institutes of Health (Bethesda, MD) Training Grant no. GM108563 (IJS), and Penn State University including USDA (Kansas City, MO) National Institute of Food and Agriculture Federal Appropriations under project number PEN04664 and accession number 1017181 (KJH) and project number PEN04678 and accession number 1017801 (PAB). The authors thank Danielle Andreen, Elaine Barnoff, Rebecca Bomberger, Shoshanna Brody, Cayden Confer, Ahmed El-Zennary, Molly Hensley, Carly King, Michael Alberto Lopez, Megan Moran, Michael Morgan, Annie Schmidt, Lucas Watson, and Bailey Winslow for technical assistance (Penn State University, University Park), along with the staff of the Penn State University Dairy Research and Teaching Center. The authors have not stated any conflicts of interest.

Publisher Copyright:
© 2023 American Dairy Association


  • circadian
  • daily rhythm
  • lactation
  • milk synthesis
  • nutrient entrainment

PubMed: MeSH publication types

  • Journal Article


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