title: The effect of dietary energy source on serum concentration of insulin-like growth factor-I growth hormone, insulin, glucose, and fat metabolites in weanling horses.
abstract: Feeding diets high in soluble carbohydrates to growing horses has been implicated in the development of orthopedic diseases; as a result, substitution of dietary fat for soluble carbohydrates has received attention. Because IGF-I is integral to growth and cartilage development and because it is influenced by nutrition, we evaluated the effect of dietary fat substitution on metabolic endpoints and circulating GH and IGF-I in growing horses. Twelve Quarter Horse weanlings, four female and eight male, 151 to 226 d old, were blocked by sex and age and assigned to two treatment groups. Group one (CARB; n = six) was fed a concentrate containing 2.21% fat and 33.9% starch; group two (FAT; n = six) was fed a concentrate containing 10.3% fat and 24.0% starch. Both concentrates contained 3.0 Mcal/kg of DE and 16% CP. Brome hay also was fed. Diets were fed at 0800 and 1600 for 60 d. On d 0, 30, and 60, blood samples were obtained via a jugular catheter from 1 h before until 5 h after the morning feeding. Serum was analyzed for glucose, insulin, GH, IGF-I, NEFA, and total cholesterol (CHOL). Neither ADG (0.85 +/- 0.04 and 0.84 +/- 0.04 kg) nor concentrate DMI (4.04 +/- 0.12 and 4.03 +/- 0.12 kg/d) differed between treatments. There were consistent increases in glucose and insulin in response to feeding on d 0, 30, and 60 for both groups. On d 30, the glucose response to feeding was less (P = 0.07) over time in FAT vs. CARB; however, there were no significant treatment x time effects on d 0 or 60. On d 60, the insulin response to feeding was less (P < 0.05) over time in FAT compared with CARB; however, there was no treatment x time effect on d 0 or 30. Serum CHOL concentrations did not differ between groups on d 0. Horses in the FAT group had increased CHOL concentrations on d 30 and 60 compared with CARB (P < 0.01). Although treatment x time interactions were noted for GH on d 30 and 60 (P < 0.05), only transient and inconsistent differences in the secretory profiles between CARB and FAT treatments were evident at those sampling times. Serum NEFA and IGF-I did not differ between treatments on d 0, 30, or 60. These results suggest that dietary energy source, at least at the level used in this study, did not affect foal growth performance or serum IGF-I and NEFA concentrations. Fat substitution increased serum CHOL and variably affected serum GH, glucose, and insulin concentrations in response to feeding.
authors.affiliation: Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506-0201, USA.
authors.forename: J K
authors.initials: JK
authors.lastname: Ropp
authors.forename: R H
authors.initials: RH
authors.lastname: Raub
authors.forename: J E
authors.initials: JE
authors.lastname: Minton
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D002784:Cholesterol / Q000097:blood; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000378:metabolism; D004041:Dietary Fats / Q000008:administration & dosage* / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D013006:Growth Hormone / Q000097:blood*; D006736:Horses / Q000097:blood* / Q000254:growth & development; D007328:Insulin / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D011897:Random Allocation; D014886:Weaning
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D002784:Cholesterol