CHANGES IN CONCENTRATIONS OF HORMONES, METABOLITES, AND AMINO-ACIDS IN PLASMA OF ADULT HORSES RELATIVE TO OVERNIGHT FEED DEPRIVATION FOLLOWED BY A PELLET-HAY MEAL FED AT NOON
Cl. Depew et al., CHANGES IN CONCENTRATIONS OF HORMONES, METABOLITES, AND AMINO-ACIDS IN PLASMA OF ADULT HORSES RELATIVE TO OVERNIGHT FEED DEPRIVATION FOLLOWED BY A PELLET-HAY MEAL FED AT NOON, Journal of animal science, 72(6), 1994, pp. 1530-1539
Experiment 1 was conducted to characterize the concentrations of prola
ctin, growth hormone (GH), cortisol, insulin, glucagon, glucose, nones
terified fatty acids (NEFA), urea N, and 10 indispensable amino acids
in the plasma of mares (n = 8) and stallions (n = 8) during the last 4
h of a 19-h period of feed deprivation and for 8 h after a noon meal.
Experiment 2 was similar to Exp. 1 except that only stallions (n = 8)
were used, and they were either fed (n = 4) or not fed (n = 4) at noo
n in a 2 x 2 Latin square design conducted over two sampling days 7 d
apart. In Exp. 1, increases (P < .01) after feeding were observed for
plasma concentrations of prolactin, cortisol, insulin, glucagon, gluco
se, urea N, and all amino acids except methionine; NEFA concentrations
decreased (P < .01) after feeding. Episodic increases in GH concentra
tions were observed for most horses but were not associated with eithe
r feeding or gender (P > .1). Plasma urea N concentrations were higher
(P < .025) overall in stallions than in mares, and the rise in prolac
tin concentrations after feeding was greater (P < .01) in stallions th
an in mares. In Exp. 2, meal-associated increases (P < .01) were obser
ved for plasma concentrations of prolactin, insulin, glucagon, and glu
cose; NEFA concentrations decreased (P < .01). Except for cortisol, no
hormone or metabolite varied with time across days when the stallions
were not fed (P > .1), indicating that there was no inherent diurnal
or feeding schedule-associated fluctuations in their concentrations. C
ortisol concentrations varied(P < .02) over time but did not differ (P
> .1) between fed and nonfed stallions. Again, GH concentrations were
episodic but did not differ (P > .1) between fed and nonfed stallions
. The lack of feeding effects on GH secretion in horses is similar to
the response in pigs but differs from that in ruminants, in which GH c
oncentrations generally decline after feeding.