Plasma concentrations of metabolic hormones in high and low producing dairy cows.
Concentrations of insulin, glucagon, growth hormone, adrenocorticotropin, and cortisol were determined in plasma samples obtained at 20-min intervals for 6 h from low and high producing dairy cows at d 30 and 90 postpartum. Four nonpregnant, nonlactating cows also were sampled. Insulin concentrations were reduced at d 30 in both groups of lactating cows compared with concentrations in nonlactating cows; glucagon concentrations were unchanged. The molar insulin: glucagon was reduced at d 30 in both groups and at d 90 for low, but not high producers. Growth hormone concentrations were higher at d 30 in high producers than at d 90, in low producers at d 30, and higher than in nonlactating cows. Cortisol concentrations were lower in high producing cows at d 30 than at d 90 or in nonlactating cows due to a reduced pulse amplitude. No differences were observed for adrenocorticotropin. Reduced molar insulin: glucagon may be an integral response of the cow to lactation, while the difference in the insulin: glucagon for high and low producers at d 90 postpartum may indicate a continued need for a gluconeogenic stimulus in low producers. The elevated growth hormone and low cortisol concentrations likely participate in the enhanced production observed in high producing dairy cows.
Sartin
J L
JL
Department of Physiology and Pharmacology, College of Veterinary Medicine, Auburn University 36849.
Kemppainen
R J
RJ
Cummins
K A
KA
Williams
J C
JC
D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D002417:Cattle / Q000097:blood*; D005260:Female; D005934:Glucagon / Q000097:blood; D013006:Growth Hormone / Q000097:blood; D006854:Hydrocortisone / Q000097:blood*; D007328:Insulin / Q000097:blood; D007774:Lactation / Q000097:blood*; D010187:Pancreatic Hormones / Q000097:blood*; D010908:Pituitary Hormones, Anterior / Q000097:blood*; D011247:Pregnancy
D007328:Insulin; D010187:Pancreatic Hormones; D010908:Pituitary Hormones, Anterior; D000324:Adrenocorticotropic Hormone; D013006:Growth Hormone; D005934:Glucagon; D006854:Hydrocortisone