DOI: 10.5061/dryad.rjdfn2zp5
title: Supplemental data for: Daily rhythms of glucose, insulin and nonesterified fatty acid responses to an intravenous glucose tolerance test in dairy cows

description: In non-ruminant species, glucose tolerance and insulin sensitivity are
 known to be regulated by circadian rhythms, which are repeating ~24 h
 cycles that govern many aspects of behavior, physiology, and metabolism.
 However, it is unknown if these rhythms exist in dairy cows. Our objective
 was to determine the fit of a daily rhythm of glucose, insulin, and
 nonesterified fatty acid clearance rates independent of daily patterns of
 nutrient intake. To accomplish our objective, 12 multiparous lactating
 Holstein cows were enrolled in a within-subject design conducted over two
 experimental periods (n = 6/period). Within each period, cows were
 subjected to intravenous glucose tolerance tests (IVGTT) representing
 0300, 0900, 1500 and 2100 h. The 0900 and 2100 h IVGTT were performed 36 h
 apart, followed by a 7-d washout and 1500 and 0300 h IVGTT performed 36 h
 apart. Cows were fed 12x/d at 2 h intervals beginning 24 h prior to the
 first IVGTT in each set until the second IVGTT in each set to stabilize
 feed intake across the day, with 1x/d feeding occurring during the washout
 period. For each IVGTT, 250 g of glucose were infused as a 50% w/v
 D-glucose solution via a jugular catheter and blood was collected at -15,
 -5, immediately before, 0, 5, 10, 15, 20, 30, 45, 60, 90, and 120 min
 relative to infusion. A linear model with the fixed effects of cosine and
 sine and random effect of cow within period was used for the outcomes of
 clearance rate, half-life, baseline concentration, time to baseline
 concentration, and area under the curve (AUC) for glucose, insulin, and
 NEFA. A zero-amplitude test was used to determine the fit of a 24 h cosine
 function and cosinor rhythmometry was used to determine the amplitude and
 acrophase of the 24 h rhythm. Insulin concentrations at baseline followed
 a diurnal rhythm. Glucose and insulin clearance rate, half-life, and AUC
 also followed a diurnal rhythm. Glucose and insulin clearance rates peaked
 at 1247 h and 0944 h, respectively. No circadian rhythm was detected for
 plasma NEFA concentrations. Results suggest that insulin-stimulated
 glucose uptake is controlled differently throughout the day by circadian
 rhythms.
description: # Supplemental data for: Daily rhythms of glucose, insulin and
 nonesterified fatty acid responses to an intravenous glucose tolerance
 test in dairy cows
 [https://doi.org/10.5061/dryad.rjdfn2zp5](https://doi.org/10.5061/dryad.rjdfn2zp5) ## Description of the data and file structure Twelve multiparous lactating Holstein cows were enrolled in a within-subject design conducted over two experimental periods (n = 6/period). Within each period, cows were subjected to intravenous glucose tolerance tests (IVGTT) representing 0300, 0900, 1500 and 2100 h. The 0900 and 2100 h IVGTT were performed 36 h apart, followed by a 7-d washout and 1500 and 0300 h IVGTT performed 36 h apart. Cows were fed 12x/d at 2 h intervals beginning 24 h prior to the first IVGTT in each set until the second IVGTT in each set to stabilize feed intake across the day, with 1x/d feeding occurring during the washout period. For each IVGTT, 250 g of glucose were infused as a 50% w/v D-glucose solution via a jugular catheter and blood was collected at -15, -5, immediately before, 0, 5, 10, 15, 20, 30, 45, 60, 90, and 120 min relative to infusion. A mixed linear model with the fixed effects of cosine and sine and random effect of cow within period was used for the outcomes of clearance rate, half-life, baseline concentration, time to baseline concentration, and area under the curve (AUC) for glucose, insulin, and NEFA. ### Files and variables \**Supplemental Table 1. **Effect of time of day on plasma glucose, insulin, and NEFA concentration response to glucose tolerance test in dairy cows.