Title page for ETD etd-08192013-113334


Type of Document Master's Thesis
Author Chartier, Erica Lynn
Author's Email Address echart1@lsu.edu
URN etd-08192013-113334
Title Effects of Meal Timing on Growth Hormone, Ghrelin, and Insulin Sensitivity in Male Holstein Calves
Degree Master of Science (M.S.)
Department Animal Science (Animal, Dairy, & Poultry Sciences)
Advisory Committee
Advisor Name Title
Williams, Cathleen Committee Chair
Hutchison, Charles Committee Member
Jenny, Bruce Committee Member
Thompson, Donald Committee Member
Keywords
  • ghrelin
  • dairy calves
  • meal timing
  • growth hormone
  • glucose metabolism
Date of Defense 2013-07-24
Availability unrestricted
Abstract
Eighteen neonatal Holstein bull calves (38.85 4.71 kg) were assigned to one of two treatments at birth to determine the effect of feeding time on growth, nutrient intake, metabolic hormone secretion, and energy metabolism. Regularly fed calves (n = 9) were fed MR daily at 0630 h, and irregularly fed calves (n = 9) at 1030, 0800, 0630, 0830, 0530, 0930, and 0730 Monday through Sunday. Body weights were measured weekly from birth to 9 weeks. Water intake, fecal scores, and starter intake were measured daily. Serial blood collections were conducted at 2, 4, 6, and 8 weeks for ghrelin and GH concentrations. Blood sample collection began one hour prior to regular feeding time (0530 h) and ended one hour post regular feeding time (0730 h), at time points 0, 15, 30, 45, 50, 55, 60, 65, 70, 75, 90, 105, and 120 minutes. An IVGTT was performed at weeks 3, 6, and 9 to assess glucose metabolism. Water intake increased (P < 0.05) in irregularly fed calves at weeks 1 and 3. A treatment by week interaction and a main effect of week were observed for ghrelin concentrations (P < 0.05), and regularly fed calves exhibited increased ghrelin concentrations at week 4 (P < 0.10). Plasma ghrelin concentrations increased with age until weaning at week 6 then decreased at week 8. An increase in GH concentrations were observed at time points t= 75 (P < 0.05), 90 (P < 0.10), and 120 (P < 0.10) min. A treatment by week interaction and a main effect of week were observed for GH concentrations (P < 0.0001). Regularly fed calves had higher GH concentrations at weeks 2 and 4 (P < 0.05). No differences were observed (P > 0.10) for glucose concentrations. Peak insulin concentrations (P < 0.05) and AUC for insulin (P < 0.10) increased as calves aged, indicating that calves become less sensitive to insulin as they develop. Results indicated that feeding time does not have an overall effect on growth, feed intake, and glucose metabolism, but does affect growth hormone concentrations.
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