Feed deprivation of mares: plasma metabolite and hormonal concentrations and responses to exercise.
Twelve light horse mares were fed a control diet that provided 100% of their maintenance protein and energy requirements for 7 d and were then either continued on the control diet or totally deprived of feed (with access to water) for 3 d . Plasma samples were drawn twice daily throughout the experiment, at 15-min intervals for 9 h beginning 45 h after feed removal, and at 10-min intervals around an exercise bout beginning 73 h after feed removal. Feed deprivation increased (P < or = .06) whole blood beta-hydroxybutyrate and plasma NEFA, urea N, L-lactate, and glucagon concentrations, decreased (P = .02) IGF-I concentrations, and did not change (P > .1) plasma glucose insulin, prolactin, triiodothyronine, and thyroxine concentrations. Exercise increased (P < .05) plasma NEFA, prolactin, and growth hormone (GH) concentrations in all mares. Plasma NEFA concentrations increased (P < .001) after exercise and remained increased in fed mares, but rapidly decreased in deprived mares (time x diet interaction, P = .006). Plasma glucose concentrations following exercise increased in deprived mares but decreased in fed mares (time x diet interaction, P = .07). The plasma prolactin response after exercise also differed between groups (P = .09). Feed-deprived mares had greater (P = .02) plasma GH concentrations before exercise (73 h after feed withdrawal) and had a greater (P < .001) GH peak at 10 min after initiation of exercise. The increase in secretion rate o GH due to feed deprivation in these mares was similar to that reported for other domestic species but was not nearly as great in magnitude.
Sticker
L S
LS
Department of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge 70803, USA.
Thompson
D L
DL
Bunting
L D
LD
Fernandez
J M
JM
DePew
C L
CL
Nadal
M R
MR
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005508:Food Deprivation / Q000502:physiology*; D005934:Glucagon / Q000097:blood; D013006:Growth Hormone / Q000097:blood*; D006736:Horses / Q000097:blood* / Q000502:physiology*; D006885:Hydroxybutyrates / Q000097:blood; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D007773:Lactates / Q000097:blood; D010805:Physical Conditioning, Animal / Q000502:physiology*; D011388:Prolactin / Q000097:blood*; D013974:Thyroxine / Q000097:blood; D013997:Time Factors; D014284:Triiodothyronine / Q000097:blood; D014508:Urea / Q000097:blood
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D006885:Hydroxybutyrates; D007328:Insulin; D007773:Lactates; D014284:Triiodothyronine; D007334:Insulin-Like Growth Factor I; D014508:Urea; D011388:Prolactin; D013006:Growth Hormone; D005934:Glucagon; D013974:Thyroxine