RESPONSE OF MILK-YIELD, PLASMA-CORTISOL, AMINO-ACIDS, UREA AND GLUCOSE TO A SINGLE LOW-DOSE ADMINISTRATION OF ADRENOCORTICOTROPIC HORMONE IN LACTATING COWS
Bb. Ndibualonji et al., RESPONSE OF MILK-YIELD, PLASMA-CORTISOL, AMINO-ACIDS, UREA AND GLUCOSE TO A SINGLE LOW-DOSE ADMINISTRATION OF ADRENOCORTICOTROPIC HORMONE IN LACTATING COWS, Veterinary research, 26(1), 1995, pp. 32-42
An experiment was conducted to determine the effects of a single low-d
ose administration of adrenocorticotrophic hormone (ACTH) on milk yiel
d, plasma cortisol, free amino acids, urea and glucose in lactating co
ws. The animals were treated with either 6 IU synthetic ACTH or 5 mi p
hysiological saline (control) administered intravenously via a jugular
vein catheter. Blood was withdrawn 60 and 5 min pretreatment (baselin
e), and 10, 20, 30, 60, 120, 180, 240, 300, 360, and 420 min post-trea
tment. A rapid positive response (P < 0.05) in plasma cortisol occurre
d within 10 min of administration of 6 IU ACTH. The maximum increase i
n plasma cortisol concentration occurred at 1 h post-ACTH treatment an
d plasma cortisol returned to baseline 4 h later. Until 7 d after ACTH
administration, no effect on milk yield was recorded. In comparison w
ith the saline-treated group, the ACTH-treated group exhibited a signi
ficant (P < 0.05) increase in the plasma concentrations of 3-methylhis
tidine, glycine, histidine, isoleucine, leucine, lysine, valine, and g
lucose. In contrast, the concentrations of alanine, aspartate, glutama
te, glutamine and proline decreased significantly (P < 0.05) after ACT
H treatment. Hormone administration had no effect on the plasma argini
ne, asparagine, methionine, phenylalanine, serine, threonine, tyrosine
, and urea. These results demonstrate that the bovine species behaves
like other mammalians with respect to its metabolic response to stress
. Thus, during stress, ACTH increases adrenal cortical activity which,
in turn, stimulates protein catabolism in muscle and gluconeogenesis
from some non-essential amino acids.