Effect of increasing milk feeding frequency of an elevated plane of nutrition on glucose and insulin kinetics in male Holstein calves both before and after weaning

The objective of this study was to investigate how feeding elevated levels of milk replacer before weaning, at different feeding frequencies, could influence glucose and insulin kinetics both before and after weaning. Ten male Holstein calves (42.2 kg ± 1.8 birth weight) were randomly assigned to 2 treatments whereby calves were offered 8 L of milk replacer (150 g/L; 26% CP and 18% CF) per day in two (2x) or four feedings (4x) via an automated feeding system. Calves were gradually stepped down by 1 L/d from wk 7 until weaning on wk 8 (0 L). Postprandial blood samples were collected on wk 4 and 7 via jugular catheters during the 1000-h meal every 30 min up to 240 min after feeding. A glucose tolerance test was conducted on wk 4, 7, and 10 via the jugular catheter the day following the postprandial measurements, with 540 mg glucose/ kg BW0.75 infused after a 12-h feed restriction. Statistics were determined using SAS PROC MIXED and any data not normally distributed was logarithmically transformed. Postprandial glucose area under the curve over 240 min (AUC240) tended (P = 0.06) to differ between treatments overall (2x: 383.51 ± 60.08 mmol/L; 4x: 246.68 ± 64.2 mmol/L) but both treatments were able to adequately control glycemia. Postprandial insulin AUC240 differed (P = 0.01) by treatment with 2x calves (13,808 ± 3,136 µU/mL) having higher insulin concentrations compared with 4x calves (4,716 ± 3,250 µU/ mL), and both treatments demonstrated a decrease in insulin AUC240 (P < 0.01) with increasing age (wk 4: 14,287 ± 2,818 µU/mL; wk 7: 4,237 ± 2,686 µU/mL), which can most likely be attributed to meal size relative to calf BW. Additionally, there was no effect observed for any of the measurements (time to maximum concentration, maximum concentration, AUC240, basal concentration, or change in concentration) for the glucose tolerance test between treatments or across ages, suggesting that feeding frequency in this study had no effect on insulin sensitivity. These findings suggest that feeding 8 L/d at a frequency of 2x or 4x are both viable feeding methods that do not compromise insulin sensitivity.