title: Dietary protein and(or) energy restriction in mares: plasma glucose, insulin, nonesterified fatty acid, and urea nitrogen responses to feeding, glucose, and epinephrine.
abstract: Sixteen light horse mares (8 to 9 yr of age; 457 to 579 kg BW) were fed Bermudagrass hay and a corn/cottonseed hull-based supplement formulated to contain either 100% (control) or 50% (restricted) of the protein and(or) energy requirements for maintenance in a 2 x 2 factorial arrangement of treatments. Daily measurements of intake, BW, and plasma hormones and metabolites were made for 33 d. Plasma glucose, insulin, NEFA, and urea N were measured in hourly samples drawn on d 27, and parallel with an i.v. glucose tolerance test (IVGTT) and epinephrine challenge on d 29. Energy restriction increased daily NEFA concentrations (P < .001) and urea N (P = .013), whereas protein restriction decreased (P = .002) urea N concentrations. These effects of protein and energy restriction occurred within 24 h and were consistent (day effect, P > .1) throughout the remaining 24 d. Normal meal consumption elevated plasma glucose, insulin, and urea N concentrations (time effect, P < .08). Plasma NEFA concentrations did not change after feeding in mares fed control energy, but decreased in mares fed restricted energy (energy x time interaction, P = .005). After IVGTT, areas under the curve for plasma glucose and insulin were smaller in mares fed restricted protein (P < .05), whereas glucose area was larger in mares fed restricted energy (P = .009). After epinephrine injection, energy restriction increased the initial magnitude of the NEFA response, but after 50 min, reduced plasma NEFA below pre-injection concentrations (energy x time interaction, P = .06).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Animal Science, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803.
authors.forename: L S
authors.initials: LS
authors.lastname: Sticker
authors.forename: D L
authors.initials: DL
authors.lastname: Thompson
authors.forename: L D
authors.initials: LD
authors.lastname: Bunting
authors.forename: J M
authors.initials: JM
authors.lastname: Fernandez
authors.forename: C L
authors.initials: CL
authors.lastname: DePew
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001806:Blood Urea Nitrogen; D001835:Body Weight / Q000187:drug effects / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology; D018753:Diet, Protein-Restricted / Q000592:standards / Q000662:veterinary; D004044:Dietary Proteins / Q000008:administration & dosage / Q000592:standards*; D004435:Eating / Q000502:physiology*; D002149:Energy Intake / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology; D004837:Epinephrine / Q000008:administration & dosage / Q000494:pharmacology*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology*; D005951:Glucose Tolerance Test / Q000662:veterinary; D006736:Horses / Q000097:blood / Q000378:metabolism*; D007275:Injections, Intravenous; D007328:Insulin / Q000097:blood
chemical_list: D001786:Blood Glucose; D004044:Dietary Proteins; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D005947:Glucose; D004837:Epinephrine