PS4-19. Yearling-ewe Insulin Sensitivity After Mid-gestation Maternal Heat Stress.

Abstract Nineteen yearling ewes born from either nine gestational heat stress ewes or from nine gestational thermoneutral ewes were evaluated to determine insulin resistance. Ewes were randomly assigned to either heat stress or thermoneutral gestational conditions during mid gestation for approximately 39 days. At lambing lambs were separated from their dams and bottle-fed pooled colostrum for 24 hours. After the initial colostrum feeding lambs were bottle-fed ad libitum until weaned at eight weeks. Immediately after weaning lambs were relocated to external pen and fed ad libitum diet of alfalfa hay and grazed pasture (8 hours a day). After 18 months of growth lambs were tested for Glucose-stimulated insulin secretion (GSIS) and insulin tolerance test (ITT). Yearling showed no difference in insulin sensitivity at 18 months however there was a difference (p < 0.05) in GSIS as well as a difference in initial insulin concentration (p < 0.05). After these tests yearling lambs were euthanized, and mammary gland were carefully removed. Heat stress exposed yearling lambs had smaller mammary glands (p < 0.5) at eighteen months of age compared to control lambs. Exposure to high temperatures and humidity during gestational was shown to have long term metabolic and physiological impacts on their offspring over a year after their birth. Recommendation for agricultural regions of strenuous environmental conditions would indicate a benefit of programing breeding to avoid these periods during critical gestation times.