Date of Completion

Spring 5-1-2013

Thesis Advisor(s)

Steven Zinn

Honors Major

Animal Science

Disciplines

Animal Sciences

Abstract

Maternal hormones impact fetal growth and development through their effect on nutrient partitioning and placental development. Maternal diet is one factor regulating maternal hormone concentrations. We hypothesized that during gestation, diet alters concentrations of maternal metabolic hormones. Pregnant ewes (n=36; 12/treatment) were individually fed 1 of 3 diets [100% (CON), 140% (OVER), or 60% (RES) NRC requirements] from wk 5 of gestation until parturition. Weekly blood samples (20 mL) were obtained via jugular venipuncture and BW was measured. Concentrations of GH, IGF-I and leptin were determined by RIA. Insulin was determined by ELISA. Data were analyzed using ANOVA. By the end of gestation (wk 20), RES ewes (89.3 ± 3.6 kg) were lighter (P < 0.01) and OVER ewes (119.7 ± 3.6 kg) were heavier (P < 0.1) than CON ewes (112.9 ± 3.6 kg). However, compared with CON ewes (0.27 ± 0.01 kg), ADG was increased (P < 0.01) in OVER ewes (0.35 ± 0.01 kg) and decreased (P < 0.01) in RES ewes (0.12 ± 0.01 kg). Concentrations of GH were greater (P < 0.01) in RES ewes (6.4 ± 0.6 ng/mL) than CON ewes (3.2 ± 0.6 ng/mL) and OVER ewes (2.3 ± 0.6 ng/mL). Average concentrations of IGF-I were greater (P < 0.1) in OVER ewes (197.7 ± 14.5 ng/mL) compared with CON (163 ± 14.5 ng/mL) and RES (146.35 ± 14.5 ng/mL) ewes, but there was no difference between CON and RES ewes (P < 0.42). Overfeeding ewes resulted in decreased (P < 0.01) IGFBP-2 concentration (0.53 ± 0.12 AU) compared with CON ewes (0.97 ± 0.10 AU), while there was no effect (P < 0.7) of underfeeding ewes on IGFBP-2 concentration (0.93 ± 0.06 AU). Average IGFBP-3 concentrations were 1.81 ± 0.14, 1.64 ± 0.10, and 1.99 ± 0.14 AU in CON, RES, and OVER ewes, respectively, and there were no associated treatment effects (P > 0.3). Average concentrations of insulin were greater (P < 0.01) in OVER ewes (0.61 ± 0.7 ng/mL) than RES (0.31 ± 0.7 ng/mL) and CON (0.32 ± 0.7 ng/mL) ewes. Leptin averaged 2.3 ± 1.4, 1.5 ± 1.4, and 4.3 ± 1.4 ng/mL in CON, RES, and OVER ewes, respectively, but there were no differences in leptin due to diet (P > 0.32). In conclusion, poor maternal diet during gestation affects circulating concentrations of GH, IGF-I, IGFBP-2, and insulin, and this may contribute to developmental changes in the fetus.

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