Effects of Maternal Nutrient Restriction During Gestation on LH Production in the Female Bovine Fetus

Gestational nutrient restriction causes epigenetic and phenotypic changes that affect multiple physiological processes in the offspring. Gonadotropes, the cells in the anterior pituitary that secrete luteinizing hormone (LH) and follicle-stimulating hormone (FSH), are particularly sensitive to nutritional changes during fetal development. Our objective herein was to investigate the effects of gestational nutrient restriction on LH protein content and number of gonadotropes in the fetal bovine pituitary. We hypothesized that moderate nutrient restriction during mid to late gestation decreases pituitary LH production, which is associated with a reduced number of gonadotropes. Embryos were produced in vitro with X-bearing semen from a single sire then split to generate monozygotic twins. Each identical twin was transferred to a virgin dam yielding four sets of female twins. At gestational d 158, the dams were randomly assigned into two groups, one fed 100% NRC requirements (control) and the other fed 70% of NRC requirements (restricted) during the last trimester of gestation, ensuring each pair of twins had one twin in each group. At gestational d 265, the fetuses (n = 4/group) were euthanized by barbiturate overdose, and the pituitaries were collected. Western blots were performed using an ovine LH-specific antibody (Dr. A.F. Parlow, NIDDK). The total LH protein content in the pituitary tended to be decreased in the restricted fetuses compared to controls (P < 0.10). However, immunohistochemistry analysis of the pituitary did not reveal any significant changes in the total number of LH-positive cells (control = 460±23 cells/0.5 mm2; restricted = 496±45 cells/0.5 mm2, P = 0.58). In conclusion, while maternal nutrient restriction during gestation resulted in a trend of reduced LH content in the fetal pituitary, immunohistological findings suggest that these changes are likely related to the individual potential of each gonadotrope to produce LH, rather than alterations in cell differentiation during fetal development.

PSII-30 Effects of Prenatal and Postnatal Nutrition on the Concentration of Neuropeptide Y in the Third Ventricle Cerebrospinal Fluid in Beef Heifers

Nutrition during gestation and early postnatal life can program developmental changes within the reproductive neuroendocrine system that persist until adult life. Here we tested the hypotheses that maternal nutrition during the second and third trimester of gestation and dietary energy intake during the juvenile period interact to affect concentrations of neuropeptide Y (NPY) in the third ventricle cerebrospinal fluid (CSF) after fasting (basal) and in response to peripheral leptin administration in heifer offspring. Bos indicus-influenced beef heifers were developed using a 3 × 2 factorial arrangement of pre- and postnatal dietary treatments. Beginning at the onset of the second trimester of gestation, pregnant Braford and Brangus cows were fed to reach body condition scores of 7.5–8 (H, obese), 5–5.5 (M, moderate), or 3–3.5 (L; very thin) during the third trimester. Heifer offspring were weaned at ~3.5 mo of age and fed to gain at either a relatively high (H; 1 kg/d) or low (L, 0.5 kg/d) rate between 4–8 mo of age, then fed a common diet subsequently. A subgroup of pubertal heifers (n = 6/group) representing 3 of the maternal × postnatal groups (HH, MH, and LL) were ovariectomized and received estradiol replacement after puberty. Cannulas were placed surgically in the third ventricle. After at least a 2-wk recovery period, heifers were fasted for 54 h and CSF was collected every 30 min for 5.5 h, including a 30-min basal and 5-h treatment period involving 3 hourly IV injections of recombinant oleptin (0.2 µg/kg BW). Basal and post-leptin NPY concentrations in the CSF did not differ (P > 0.10) among LL, MH, and HH heifers. Treatment with leptin had no effect (P > 0.10) on NPY concentration in any group. Therefore, neither the interaction of pre- and postnatal nutrition nor exogenous leptin affected third ventricle NPY tone in this experimental model.