Effects of Prenatal and Postnatal Nutrition on the Concentration of Neuropeptide Y in the Third Ventricle Cerebrospinal Fluid in Beef Heifers
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AbstractNutrition 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 7.58 (H, obese), 55.5 (M, moderate), or 33.5 (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 48 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 g/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.
