|Taylor, Joshua - Bret|
Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/6/2012
Publication Date: 8/1/2012
Citation: Meyer, A.M., Reed, J.J., Neville, T.L., Taylor, J.B., Reynolds, L.P., Redmer, D.A., Vonnahme, K.A., Caton, J.S. 2012. Effects of nutritional plane and selenium supply during gestation on visceral organ mass and indices of intestinal growth and vascularity in primiparous ewes at parturition and during early lactation.. Journal of Animal Science. 90:2733-2749. Interpretive Summary: Forage quality and availability, which are driven by climatic conditions, soil chemistry and rangeland management, can vary greatly when sheep are pregnant. Nutrient intake during pregnancy can have both positive and negative effects on the dam and the fetus. Based on the literature, the splanchnic tissues, which include the intestines and abdominal organs, change in response to stage of pregnancy and nutrient intake during pregnancy. Alterations within the splanchnic tissues could contribute to physiological and performance changes in both the ewe and the offspring. The objectives of this study were to determine the effects of deficient, adequate, or excessive macro (energy and protein) and micro (selenium) nutrients during pregnancy on the ewe at birth and during early lactation. As macro nutrient intake increased from deficient to excessive, ewe body, intestine and organ mass increased respectively. In some instances, excessive selenium intake altered responses of intestine and organ mass to macro nutrient supply. However, no toxic effects were observed when selenium was provided at >10-fold the daily requirement. These data indicate that macro nutrient supply during pregnancy will result in substantial effects on splanchnic tissues of ewes at lambing, which could impact offspring health and development.
Technical Abstract: Objectives were to investigate effects of nutritional plane and Se supply during gestation on visceral organ mass and intestinal growth and vascularization in ewes at parturition and during early lactation. Primiparous Rambouillet ewes (n = 84) were allocated to 2 × 3 × 2 factorial arrangement of treatments. Factors included dietary Se (adequate Se [ASe, 11.5 µg/kg BW] or high Se [HSe, 77.0 µg/kg BW]), nutritional plane (60% [restricted; RES], 100% [control; CON], or 140% [high; HIH]), and physiological stage at necropsy (parturition or d 20 of lactation). At parturition, lambs were removed and 42 ewes (7/treatment) were necropsied. Remaining ewes were transitioned to a common diet, which met lactation requirements, and mechanically milked for 20 d. In the absence of interactions (P > 0.10), main effects are reported. At parturition, stomach complex and liver masses were greatest for HIH, intermediate for CON, and least for RES (P < 0.02). Small intestinal mass was greater (P = 0.002) for HIH than RES and CON and greater (P < 0.01) for ASe than HSe. During early lactation, RES and CON gastrointestinal masses increased disproportionally to BW (P < 0.05). At parturition, jejunal mucosal density was less (P = 0.01) for RES than CON and HIH, whereas CON had greater (P < 0.003) jejunal mucosal RNA concentration and RNA:DNA than RES and HIH. Although there were no differences (P > 0.17) at parturition, jejunal cell percent proliferation was greatest in RES, intermediate in CON, and least in HIH (P = 0.09) at d 20 lactation. At both stages, RES had less (P = 0.01) jejunal capillary area density than HIH and less (P = 0.03) capillary surface density than CON and HIH. During lactation, jejunal capillary size was greater (P = 0.04) for ewes previously fed HSe compared with ASe. At parturition, ASe-HIH had greater (P < 0.02) jejunal mucosal endothelial nitric oxide synthase 3 (NOS3) mRNA than all other treatments and greater (P = 0.10) vascular endothelial growth factor (VEGF) than all treatments except ASe-RES. In addition, CON had less (P = 0.08) jejunal VEGF receptor-1 (FLT1) mRNA compared with RES and HIH, and ASe had greater (P = 0.003) FLT1 than HSe at parturition. Ewes fed HIH had greater (P = 0.04) jejunal VEGF receptor-2 (KDR) mRNA compared with RES. Results indicate that maternal intestinal growth and vascularization are responsive to nutritional plane and dietary Se during gestation and undergo changes postpartum when under similar lactational management.