title: Plasma growth hormone, insulin-like growth factor, insulin, and thyroid hormone association with body protein and fat accretion in steers undergoing compensatory gain after dietary energy restriction.
abstract: Eighteen Chianina crossbred steers were used to examine the interrelationship between hormonal status and empty body protein (EBPRT) and fat (EBFAT) accretion during an 88-d controlled realimentation (REAL; DMI was adjusted weekly on an individual BW basis) period. Body composition was determined by monitoring endogenous whole-body 40[K]. At the end of restriction (REST) and on d 31 and 59 of REAL blood samples were taken and analyzed for concentrations of growth hormone (GH), IGF-I, IGF-II, insulin (INS), thyroxine (T4), triiodothyronine (T3), reverse triiodothyronine (rT3), nonesterified fatty acids (NEFA), glucose, and urea nitrogen. Depositions of EBPRT and EBFAT were decreased (P < .001) in REST (92 d) animals compared with nonrestricted (NR) controls. During REST, plasma levels of glucose, IGF-I, INS, T4, T3, and rT3 were decreased (P < .05); plasma urea nitrogen (PUN), NEFA, and GH levels were increased (P < .05), and IGF-II concentrations were similar between REST and NR steers. A transient compensatory response in BW gain and protein deposition occurred in repleted steers between d 35 and 62 of REAL. During this period, PUN levels markedly declined (P < .01) in REAL steers and glucose concentration increased (P < .01) to levels similar to those in NR controls. This response prevailed even though apparent digestible nutrients were decreased in repleted animals. During energy repletion, plasma levels of T4, T3, rT3, IGF-I, and INS were positively, and of GH was negatively, correlated with EBPRT and EBFAT gain in repleted animals. Unlike IGF-I, IGF-II was not correlated with compensatory body growth. These results suggest that compensating steers are more metabolically efficient; rapid body tissue gain occurs during a period of reduced nutrient digestibility. Additionally, plasma levels of IGF-I, GH, INS, and thyroid hormones, but not of IGF-II, are markedly affected by alteration of energy intake and are highly correlated with empty body gain and protein deposition in compensating late-maturing steers.
authors.affiliation: Department of Animal Sciences, University of Missouri, Columbia 65211.
authors.forename: J M
authors.initials: JM
authors.lastname: Hayden
authors.forename: J E
authors.initials: JE
authors.lastname: Williams
authors.forename: R J
authors.initials: RJ
authors.lastname: Collier
mesh_terms: D000273:Adipose Tissue / Q000254:growth & development; D000821:Animal Feed; D000818:Animals; D001806:Blood Urea Nitrogen; D001823:Body Composition / Q000502:physiology*; D002417:Cattle / Q000097:blood / Q000254:growth & development*; D004063:Digestion; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005508:Food Deprivation / Q000502:physiology*; D013006:Growth Hormone / Q000097:blood; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D008297:Male; D024510:Muscle Development; D013963:Thyroid Hormones / Q000097:blood; D015430:Weight Gain / Q000502:physiology*
chemical_list: D005230:Fatty Acids, Nonesterified; D007328:Insulin; D013963:Thyroid Hormones; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone