Off-campus UNL users: To download campus access dissertations, please use the following link to log into our proxy server with your NU ID and password. When you are done browsing please remember to return to this page and log out.
Non-UNL users: Please talk to your librarian about requesting this dissertation through interlibrary loan.
Endocrine and metabolic responses to plane of protein and energy nutrition in sheep
Abstract
Three trials were conducted to measure the effect of protein and energy nutrition on the endocrine and metabolic responses in sheep. In all trials, diets first-limiting in energy or metabolizable protein were fed to maintain body weight for 5 or 7 wk. In mature wethers in Trial 1, serum insulin-like growth factor-I (IGF-I) decreased 30% within 1 wk of restriction, but returned to control levels within 1 wk of repletion. Plasma somatotropin (ST) increased in protein restricted, but not energy restricted, lambs during restriction and returned to control levels after 1 wk of repletion. In Trial 2 with young lambs, results were similar to those observed in Trial 1. In both trials, serum IGF-I concentration over restriction and repletion was correlated to gain (r =.62 and r =.61). Western-ligand blots of serum identified IGF binding proteins (IGFBP) at M$\sb r$ 39 to 40, 35, 28.5 to 31.5, and 24 kDa, corresponding to IGFBP-3,-2,-1, and -4. No IGFBP appeared to be modulated by nutrition. Trial 3 used a serial slaughter design to measure response of mass of visceral organs and metabolic activity of liver and jejunum as well as hormonal levels. Lambs restricted in energy or protein had lighter livers and carcasses than controls after a 7-wk restriction. Liver mass, as a percentage of empty body weight, was fully repleted by d-2 of realimentation. During restriction, hepatic in vitro O$\sb2$ consumption increased when expressed on a gram of tissue basis but decreased when expressed as the whole organ. Hepatic O$\sb2$ consumption was governed by the mass of the liver. Serum IGF-I decreased 30% by restriction, but was elevated above controls at d-14 of repletion. Insulin decreased and ST increased by protein but not energy restriction. There were no changes in IGF-n concentration. Serum triiodothyronine was decreased 30% after 3 wk of restriction and returned to control levels by d-6 of repletion. Serum thyroxine decreased immediately by restriction and remained low throughout repletion. Dynamic changes in metabolic and endocrine status adapted sheep to plane of nutrition and enabled their survival.
Subject Area
Livestock|Anatomy & physiology|Animals|Nutrition
Recommended Citation
Wester, Timothy J, "Endocrine and metabolic responses to plane of protein and energy nutrition in sheep" (1994). ETD collection for University of Nebraska-Lincoln. AAI9425311.
https://digitalcommons.unl.edu/dissertations/AAI9425311