The placenta is the organ that transports nutrients, respiratory gases, and wastes between the maternal and fetal systems. Consequently, placental blood flow and vascular development are essential components of normal placental function and are critical to fetal growth and development. Normal fetal growth and development are important to ensure optimum health of offspring throughout their subsequent life course. In numerous sheep models of compromised pregnancy, in which fetal or placental growth, or both, are impaired, utero-placental blood flows are reduced. In the models that have been evaluated, placental vascular development also is altered. Recent studies found that treatments designed to increase placental blood flow can 'rescue' fetal growth that was reduced due to low maternal dietary intake. Placental blood flow and vascular development are thus potential therapeutic targets in compromised pregnancies.

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To examine effects of nutritional plane and Se supplementation on colostrum quality and mammary development, individually fed, pregnant Rambouillet ewe lambs were allotted randomly to 1 of 6 treatments in a 2 x 3 factorial arrangement. Main effects included dietary Se level, which began at breeding (d = 0) [adequate Se (9.5 mug/kg of BW) vs. high Se (81.8 mug/kg of BW)], and plane of nutrition, which began at d 50 of gestation [60% (RES), 100% (CON), and 140% (HIGH) of requirements]. Upon parturition, lambs were immediately separated from dams and weighed. Three hours after lambing, colostrum yield was determined, and samples were obtained for components and immunoglobulin G (IgG) analysis. Ewes were slaughtered within 24 h of parturition, and mammary tissues were collected for determination of alveolar secretory epithelial cell proliferation index and luminal area. Gestation length was reduced (P < 0.01) in HIGH ewes compared with RES and CON ewes. Although birth weights were reduced (P < 0.01) in RES and HIGH compared with CON ewes, there was little effect of diet on placental size. Mammary gland weight was reduced (P /= 0.15) on mammary gland weight, colostrum quantity, or IgG concentration in pregnant ewe lambs. Improper nutrition from mid to late pregnancy in ewe lambs altered colostrum quality and quantity and reduced offspring birth weight, which may have negative implications for lamb health and survival during the early postnatal period.

Growing pigs (initial BW 14.3 +/- 1.2 kg) were fed isocaloric (3.26 Mcal of ME/kg) and isonitrogenous (16% CP) diets containing either 0 (low fiber, LF; n = 4) or 10% (high fiber, HF; n = 4) wheat straw for ad libitum intake for 14 d. On d 14, each pig was injected i.v. with bromodeoxyuridine (BrdU, a thymidine analog; 5 mg/kg) and was slaughtered 1 h later. Visceral organs (liver, pancreas, and intestines) were weighed, and tissue samples were obtained. Feed consumption, daily gain, gain: feed, and final BW did not differ between treatments. Neither visceral weights nor visceral weights per unit of eviscerated BW were affected by diets. Tissue concentrations of DNA (milligrams/gram of tissue) were lower (P < .03) in HF than in LF only for jejunum, ileum, and liver. Contents of DNA and protein (milligrams) did not differ between LF and HF for intestinal segments or liver. Content of RNA (milligrams) was greater (P < .04) in HF than in LF only for colon. The number of crypt cell nuclei that were labeled with BrdU (indicating DNA synthesis and thus cell proliferation) was increased (P < .03) in HF relative to LF for jejunum and colon. The number of epithelial cells exhibiting DNA fragmentation (indicating programmed cell death) was greater (P < .07) in the HF than in the LF group for jejunum and ileum. Width of intestinal villi was increased (P < .10) in HF vs LF for jejunum and ileum. Depth of intestinal crypts was increased (P < .08) in HF vs LF for jejunum, ileum, and colon.(ABSTRACT TRUNCATED AT 250 WORDS)

To examine effects of nutrient restriction and dietary Se on maternal and fetal visceral tissues, 36 pregnant Targhee-cross ewe lambs were allotted randomly to 1 of 4 treatments in a 2 x 2 factorial arrangement. Treatments were plane of nutrition [control, 100% of requirements vs. restricted, 60% of controls] and dietary Se [adequate Se, ASe (6 microg/kg of BW) vs. high Se, HSe (80 microg/kg of BW)] from Se-enriched yeast. Selenium treatments were initiated 21 d before breeding and dietary restriction began on d 64 of gestation. Diets contained 16% CP and 2.12 Mcal/kg of ME (DM basis) and differing amounts were fed to control and restricted groups. On d 135 +/- 5 (mean +/- range) of gestation, ewes were slaughtered and visceral tissues were harvested. There was a nutrition x Se interaction (P = 0.02) for maternal jejunal RNA:DNA; no other interactions were detected for maternal measurements. Maternal BW, stomach complex, small intestine, large intestine, liver, and kidney mass were less (P < or = 0.01) in restricted than control ewes. Lung mass (g/kg of empty BW) was greater (P = 0.09) in restricted than control ewes and for HSe compared with ASe ewes. Maternal jejunal protein content and protein:DNA were less (P < or = 0.002) in restricted than control ewes. Maternal jejunal DNA and RNA concentrations and total proliferating jejunal cells were not affected (P > or = 0.11) by treatment. Total jejunal and mucosal vascularity (mL) were less (P < or = 0.01) in restricted than control ewes. Fetuses from restricted ewes had less BW (P = 0.06), empty carcass weight (P = 0.06), crown-rump length (P = 0.03), liver (P = 0.01), pancreas (P = 0.07), perirenal fat (P = 0.02), small intestine (P = 0.007), and spleen weights (P = 0.03) compared with controls. Fetuses from HSe ewes had heavier (P < or = 0.09) BW, and empty carcass, heart, lung, spleen, total viscera, and large intestine weights compared with ASe ewes. Nutrient restriction resulted in less protein content (mg, P = 0.01) and protein:DNA (P = 0.06) in fetal jejunum. Fetal muscle DNA (nutrition by Se interaction, P = 0.04) concentration was greater (P < 0.05) in restricted ewes fed HSe compared with other treatments. Fetal muscle RNA concentration (P = 0.01) and heart RNA content (P = 0.04) were greater in HSe vs. ASe ewes. These data indicate that maternal dietary Se may alter fetal responses, as noted by greater fetal heart, lung, spleen, and BW.