Insulin and glucagon secretion in lactating cows during heat exposure

• Published in: Journal of animal science Vol. 76; no. 8; pp. 2182 - 2189
• Main Authors: Itoh, F, Obara, Y, Rose, M.T, Fuse, H, Hashimoto, H
• Format: Journal Article
• Language: English
• Published: Savoy, IL Am Soc Animal Sci 01-08-1998; American Society of Animal Science; Oxford University Press
• Subjects: Animals; arginine; Arginine - administration & dosage; Arginine - pharmacology; Biological and medical sciences; blood glucose; Blood Glucose - metabolism; blood lipids; blood plasma; Body Temperature; butyrates; Butyrates - administration & dosage; Butyrates - pharmacology; Butyric Acid; Cattle; Cattle Diseases - metabolism; Cattle Diseases - physiopathology; dairy cows; Dairy farms; dry matter; Endocrine system; fatty acids; Fatty Acids, Nonesterified - blood; feed intake; Female; Fundamental and applied biological sciences. Psychology; glucagon; Glucagon - blood; Glucagon - metabolism; glucose; Glucose - administration & dosage; Glucose - pharmacology; Heart Rate; Heat; heat stress; Hormone metabolism and regulation; hormone secretion; Hot Temperature - adverse effects; Infusions, Intravenous - veterinary; Injections, Intravenous - veterinary; Insulin; Insulin - blood; Insulin - metabolism; Insulin Secretion; intravenous injection; lactation; Lactation - metabolism; lactose; Milk - chemistry; Milk - metabolism; milk fat percentage; milk fat yield; milk protein percentage; milk protein yield; milk yield; Pregnancy. Parturition. Lactation; Respiration; respiration rate; solids not fat; Stress, Physiological - metabolism; Stress, Physiological - physiopathology; Stress, Physiological - veterinary; total solids; Vertebrates: reproduction; Pancreatic hormone; Bovine; Glucagon; Lactation; Peptide hormone; Temperature effect; Insulin; Endocrine secretion; Vertebrata; Mammalia; Female; Artiodactyla; Ungulata
• ISSN: 0021-8812; 1525-3163; 0021-8812
• DOI: 10.2527/1998.7682182x

Heat stress affects endocrine systems in cows. This study investigated changes in insulin and glucagon secretion between thermoneutral (TN; 18 degrees C, relative humidity [RH] 60%) and hot (28 degrees C, RH 60%) environments in lactating cows. Glucose, arginine, and butyrate were administered i.v. to four cows (mean, at 83 d postpartum) in each environment. Blood was collected via a jugular catheter at regular intervals. Heat exposure resulted in a marked increase in respiration rate and rectal temperature. A decrease in milk yield was also observed during heat exposure. Basal insulin concentrations were elevated, and basal glucose concentrations tended to be lower in the hot environment. Peak values of insulin and glucagon following the arginine injection were significantly higher in the hot than in the TN environment. The insulin peak value in response to the butyrate infusion was also higher during the heat exposure. However, insulin and glucagon responses to the glucose load were not affected by heat stress. The increase in plasma glucose concentration following arginine injection was inhibited by the heat exposure. In conclusion, heat stress resulted in a higher insulin secretion in lactating cows. Glucagon secretion in response to the arginine injection was enhanced, but the rise in plasma glucose was inhibited by heat exposure. These changes would be related to a reduction in milk yield during heat stress.