Postprandial blood hormone and metabolite concentrations influenced by feeding frequency and feeding level in veal calves

This study hypothesized that increased feeding frequency (FF) decreases problems with glucose homeostasis seen at high feeding levels (FL) in heavy veal calves. Effects of FF and FL on hormone and metabolite concentrations were studied in 15 heavy veal calves fed once (FF1; at 12:00), twice (FF2; at 12:00 and 24:00) or four times daily (FF4; at 06:00, 12:00, 18:00 and 24:00). In period 1, all calves were fed at a low FL (FLlow; 1.5 × metabolizable energy requirements for maintenance, MEm). In period 2, FF2 and FF4 calves were fed at high FL (FLhigh; 2.5 × MEm), whereas FF1 calves were still fed at FLlow. Blood was sampled every 30 min from 12:00 to 18:00 and postprandial integrated plasma hormone and metabolite concentrations (AUC12–18 h) were calculated. Glucose AUC12–18 h increased with increasing FL, but decreased with increasing FF, urea AUC12–18 h increased with increasing FL, whereas non-esterified fatty acid AUC12–18 h were unaffected by FL and FF. Insulin AUC12–18 h decreased with increasing FF and decreasing FL. Glucagon AUC12–18 h increased with increasing FL and FF. Growth hormone AUC12–18 h decreased, whereas insulin-like growth factor-1 and leptin AUC12–18 h increased with increasing FL. Mean thyroxine and 3,5,3′-triiodothyronine concentrations were modified by FF and FL. There were no FF × FL interactions, except for plasma glucose. In conclusion, postprandial hormone and metabolite responses were differentially affected by FF and (or) FL. Glucose and insulin concentrations were maximally increased at high FL and low FF. Hyperglycemia, glucosuria and excessive insulinemia were prevented by increasing FF and decreasing FL.