|Taylor, Joshua - Bret|
Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/22/2008
Publication Date: 1/22/2009
Citation: Carlson, D.B., Reed, J.J., Borowicz, P.P., Taylor, J.B., Reynolds, L.P., Redmer, D.A., Vonnahme, K.A., Caton, J.S. 2009. Effects of selenium supply and timing of nutrient restriction during gestation on maternal growth and body composition of pregnant adolescent ewes. Journal of Animal Science. 87:669-680. Interpretive Summary: Because of severe climatic conditions, pregnant sheep grazing western ranges during the winter may experience periods of limited nutrition. Furthermore, depending upon geographical location, selenium may also be limiting. Our primary objectives were to investigate the impacts of 1) restricted nutrition and 2) supplemental selenium on pregnant adolescent sheep and their fetuses. Fetal weight was impaired when ewes consumed only 60% of their recommended daily energy and protein requirements during middle and late pregnancy. Nutrient restriction during late pregnancy had a greater negative impact on fetal weight than did nutrient restriction during middle pregnancy. Nutrient restriction altered the mass of digestive tissues in pregnant ewes. High dietary selenium, from an organically-bound source, decreased heart mass but increased liver mass in pregnant ewes. Depending on level of nutrient restriction, high dietary selenium altered intestinal cell numbers. High dietary selenium affected whole-body and organ growth of pregnant ewes, but results differed depending on plane of nutrition during pregnancy.
Technical Abstract: Objectives were to examine the effects of dietary Se supplementation and nutrient restriction during defined periods of gestation on maternal adaptation to pregnancy in sheep. Sixty-four pregnant Targhee ewe lambs were assigned to 1 of 8 treatments in a 2 × 2 × 2 factorial arrangement. Treatments were dietary Se [adequate Se (ASe; 3.05 microgram/kg BW) vs. high Se (HSe; 70.4 microgram/kg BW as Se-enriched yeast)], plane of nutrition during mid- gestation [100% (M100) vs. 60% of requirements (M60)], and plane of nutrition during late gestation [100% (L100) vs. 60% of requirements (L60)]. Selenium treatments were fed throughout gestation, mid and late-gestation treatments were applied from d 50 to 90 and d 90 to 130 of gestation, respectively. Pregnant ewes were necropsied on d 132 ± 0.9 of gestation. Ewe ADG, G:F, and BCS change followed a expected pattern in response to plane of nutrition; therefore, M60 and L60 ewes had similar BW, maternal BW (MBW), and BCS at necropsy. Selenium supplementation increased ADG (P = 0.02) and G:F (P = 0.02) by M100 ewes from d 50 to 130; however, HSe decreased ADG (P < 0.01) and G:F (P = 0.02) by M60 ewes, and increased BCS loss (P = 0.06) by M60-L60 ewes from d 90 to 130. High Se decreased absolute (g; P = 0.09) and relative heart mass (g/kg MBW; P = 0.10), but increased absolute and relative mass of liver (P = 0.05) and perirenal fat (P = 0.06). High Se decreased DNA concentration (P = 0.07), cell number (P = 0.03), and proliferating cell number (P = 0.05) in the jejunum. Further, HSe decreased absolute and relative ileum mass (P = 0.07) in M60-L100 ewes. The M60 treatment increased (P = 0.01) the relative mass of full viscera, rumen, and small intestine vs. M100 ewes, whereas the L60 treatment decreased (P = 0.06) both absolute and relative masses of these organs compared with L100 ewes. Further, the M60 treatment increased (P = 0.08) the relative mass of the reticulum, omasum, jejunum, gravid uterus, and mammary gland compared with M100 ewes, whereas the L60 treatment decreased (P = 0.02) absolute mass of these organs vs. the L100 treatment. Fetal weight was decreased (P = 0.02) in L60 ewes only. The M60 treatment decreased jejunum (P = 0.03) and jejunal mucosa (P = 0.02) cellularity, whereas L60 reduced (P = 0.03) total jejunal vascularity. High Se affected whole-body and organ growth, but results obtained differed depending on plane of nutrition.