title: Substantial replacement of lactose with fat in a high-lactose milk replacer diet increases liver fat accumulation but does not affect insulin sensitivity in veal calves.
abstract: In veal calves, the major portion of digestible energy intake originates from milk replacer (MR), with lactose and fat contributing approximately 45 and 35%, respectively. In veal calves older than 4 mo, prolonged high intakes of MR may lead to problems with glucose homeostasis and insulin sensitivity, ultimately resulting in sustained insulin resistance, hepatic steatosis, and impaired animal performance. The contribution of each of the dietary energy sources (lactose and fat) to deteriorated glucose homeostasis and insulin resistance is currently unknown. Therefore, an experiment was designed to compare the effects of a high-lactose and a high-fat MR on glucose homeostasis and insulin sensitivity in veal calves. Sixteen male Holstein-Friesian calves (120±2.8kg of BW) were assigned to either a high-lactose (HL) or a high-fat (HF) MR for 13 consecutive weeks. After at least 7 wk of adaptation, whole-body insulin sensitivity and insulin secretion were assessed by euglycemic-hyperinsulinemic and hyperglycemic clamps, respectively. Postprandial blood samples were collected to assess glucose, insulin, and triglyceride responses to feeding, and 24-h urine was collected to quantify urinary glucose excretion. At the end of the trial, liver and muscle biopsies were taken to assess triglyceride contents in these tissues. Long-term exposure of calves to HF or HL MR did not affect whole-body insulin sensitivity (averaging 4.2±0.5×10-2[(mg/kg∙min)/(μU/mL)]) and insulin secretion. Responses to feeding were greater for plasma glucose and tended to be greater for plasma insulin in HL calves than in HF calves. Urinary glucose excretion was substantially higher in HL calves (75±13g/d) than in HF calves (21±6g/d). Muscle triglyceride content was not affected by treatment and averaged 4.5±0.6g/kg, but liver triglyceride content was higher in HF calves (16.4±0.9g/kg) than in HL calves (11.2±0.7g/kg), indicating increased hepatic fat accumulation. We conclude that increasing the contribution of fat to the digestible energy intake from the MR from 20 to 50%, at the expense of lactose does not affect whole-body insulin sensitivity and insulin secretion in calves. However, a high-lactose MR increases postprandial glucose and insulin responses, whereas a high-fat MR increases fat accumulation in liver but not muscle.
authors.affiliation: Department of Pediatrics, Center for Liver, Digestive and Metabolic Diseases, University Medical Centre Groningen, 9700 RB Groningen, the Netherlands. Electronic address: a.j.pantophlet@umcg.nl.
authors.forename: A J
authors.initials: AJ
authors.lastname: Pantophlet
authors.affiliation: Animal Nutrition Group, Wageningen University, 6700 AH, Wageningen, the Netherlands.
authors.forename: W J J
authors.initials: WJJ
authors.lastname: Gerrits
authors.affiliation: Centre for Medical Biomics, University Medical Center Groningen, 9700 RB, Groningen, the Netherlands.
authors.forename: R J
authors.initials: RJ
authors.lastname: Vonk
authors.affiliation: Animal Nutrition Group, Wageningen University, 6700 AH, Wageningen, the Netherlands.
authors.forename: J J G C
authors.initials: JJGC
authors.lastname: van den Borne
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D002417:Cattle / Q000502:physiology*; D004032:Diet / Q000662:veterinary; D004041:Dietary Fats / Q000378:metabolism*; D007333:Insulin Resistance; D007785:Lactose / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008297:Male
chemical_list: D004041:Dietary Fats; D007785:Lactose
keywords: fat; insulin sensitivity; lactose; veal calves