Differential effects of plane of protein or energy nutrition on visceral organs and hormones in lambs.
Modulation of somatotrophic and homeorhetic hormones, along with changes in visceral mass and metabolic activity, were measured in growing lambs restricted in energy (ER) or metabolizable protein (PR) to maintain BW for 7 wk and then repleted for 2 wk. Control lambs were fed an adequate diet for 9 wk. Serum IGF-I decreased more rapidly in PR, but both ER and PR were 70% of controls by wk 7 of restriction (P < .05) and increased above controls by d 14 of repletion. Somatotropin, increased by PR, returned to control levels upon repletion (P < .05). Insulin was decreased by PR (P < .02) but was transiently elevated above controls by repletion in ER and PR at d 2 (P < .01). Serum triiodothyronine, reduced to 70% of controls by PR and ER, returned to control levels after d 6 of repletion (P < .05). Thyroxine declined gradually to 65% of controls in ER and PR (P < .07) but did not respond to repletion. By wk 7 of restriction, liver mass in ER and PR was decreased to 50% of controls (P < .05). Return of liver mass, on an empty body weight basis, occurred by d 2 of repletion (P < .01). In vitro O2 consumption per gram of liver tissue was increased to 125% of controls by ER and PR (P < .05). Calculated whole liver O2 consumption in ER and PR was 68% of controls at wk 7 of restriction (P < .10). Protein restriction had a more immediate impact on hormones but not on visceral mass or activity compared with energy restriction. Elevated IGF-I levels, as observed in previously restricted lambs, may mediate compensatory growth in ruminants.
Wester
T J
TJ
Department of Animal Science, University of Nebraska, Lincoln 68583-0908, USA.
Britton
R A
RA
Klopfenstein
T J
TJ
Ham
G A
GA
Hickok
D T
DT
Krehbiel
C R
CR
D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001835:Body Weight / Q000502:physiology; D004044:Dietary Proteins / Q000494:pharmacology*; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology*; D013006:Growth Hormone / Q000097:blood / Q000502:physiology; D007328:Insulin / Q000097:blood / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000502:physiology; D007335:Insulin-Like Growth Factor II / Q000032:analysis / Q000502:physiology; D007421:Intestine, Small / Q000033:anatomy & histology / Q000378:metabolism / Q000502:physiology; D008099:Liver / Q000033:anatomy & histology / Q000378:metabolism / Q000502:physiology; D008297:Male; D009929:Organ Size; D010101:Oxygen Consumption / Q000502:physiology; D012756:Sheep / Q000378:metabolism / Q000502:physiology*; D013974:Thyroxine / Q000097:blood / Q000502:physiology; D014284:Triiodothyronine / Q000097:blood / Q000502:physiology
D004044:Dietary Proteins; D007328:Insulin; D014284:Triiodothyronine; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D013006:Growth Hormone; D013974:Thyroxine