Short communication: Effect of glucose infusion dose and stage of lactation on glucose tolerance test kinetics in lactating dairy cows

Abstract

The objective for this study was to determine the effect of glucose dose and days following peak milk yield on plasma glucose, serum insulin, and plasma nonesterified fatty acids (NEFA) kinetics during an intravenous glucose tolerance test (IVGTT) in lactating dairy cattle. Six lactating Holstein dairy cows (3 primiparous and 3 multiparous) were assigned to 2 squares and received 0.092, 0.15, or 0.3 g of glucose/kg of body weight (BW) during an IVGTT at 74 and 221 d in milk (DIM), representing early (post-peak) lactation and mid lactation, respectively. Treatments were applied in a replicated Latin square design using contiguous 7-d periods within each stage of lactation. Milk production and dry matter intake were determined daily during the first 6 d of each period. The IVGTT was performed on d 7. For the IVGTT, cows were prepared with indwelling catheters in each jugular vein, and blood samples were collected at −15, −10, 5, 10, 15, 20, 30, 45, 60, 90, and 120 min relative to the glucose infusion. Samples were analyzed for plasma glucose, serum insulin, and plasma NEFA concentrations. Increasing the glucose dose during the IVGTT increased plasma glucose area under the curve (AUC), decreased glucose half-life, and increased maximal plasma glucose concentrations in plasma during the IVGTT. Greater glucose dose during the IVGTT elevated serum insulin AUC and increased nadir NEFA concentrations. Maximal plasma glucose concentration during the IVGTT was lower, whereas maximum NEFA concentration, NEFA AUC, and NEFA clearance rate were greater at 74 than at 221 DIM. Only glucose half-life was responsive to stage of lactation × glucose dose effects during the IVGTT, and the decrease in glucose half-life with increasing glucose dose was greater at 74 than at 221 DIM. Glucose AUC was greater and NEFA AUC lower for cows at 74 than at 221 DIM. For the doses tested, a glucose dose greater than 0.092 g/kg of BW resulted in peak blood glucose concentration that exceeded the previously reported renal glucose excretion threshold of 8.3 mM. There is a need for accompanying data to determine if this is the case for the glucose doses evaluated in this experiment. Based on maximal peak glucose concentrations and effects on glucose half-life, we identify 0.092 g of glucose/ kg of BW (0.46 g/kg of metabolic body weight) as the preferred dose for the IVGTT for cows at 74 and 221 DIM in this study.

Effect of Rumen-Protected Glucose Supplementation on Feedlot Performance, Carcass Characteristics, and Meat Quality of Kamphaeng Saen Steers

“…In this case, if we consider that RPG increases glucose reaching the small intestine, this condition should have reduced the feed intake. The DMI results are consistent with several other studies that provided glucose, either invennously (Malacco et al, 2020) or with rumen-protected glucose products (McCarthy et al, 2020;Sauls-Hiesterman et al, 2020). ADG, FCR, and feed efficiency (G:F) did not differ significantly between regimens in this study.…”

Chronic prepartum light-dark phase shifts in cattle disrupt circadian clocks, decrease insulin sensitivity and mammary development, and are associated with lower milk yield through 60 days postpartum

“…This can be due to several factors that include the time relative to last meal, and physiological state; these baseline indices were created to measure human insulin sensitivity and adapted for cattle (Holtenius and Holtenius, 2007;De Koster et al, 2017;González-Grajales et al, 2017). There is also the concern that insulin disappearance occurs through several insulin-independent pathways including renal filtration and fetal and mammary gland uptake depending on the physiological state of the animal (González-Grajales et al, 2018;Malacco et al, 2020). Although the gold standard of measuring insulin sensitivity in dairy cows has been the use of the insulin euglycemic clamp, several studies have evaluated insulin sensitivity using IVGTT and RQUICKI alone (Pires et al, 2007;Mann et al, 2016).…”