Effects of plane of nutrition and selenium supply during gestation on ewe and neonatal offspring performance, body composition, and serum selenium.

To investigate the effects of nutritional plane and Se supply during gestation on ewe and offspring performance and body composition, 84 Rambouillet ewe lambs (age = 240 +/- 17 d, BW = 52.1 +/- 6.2 kg) were allocated to a 2 x 3 x 2 factorial arrangement of treatments. Factors included Se [adequate Se (ASe, 11.5 microg/kg of BW) or high Se (HSe, 77.0 microg/kg of BW)] initiated at breeding, nutritional plane [60% (restricted, RES), 100% (control, CON), or 140% (high, HIH) of NRC requirements] initiated at d 40 of gestation, and physiological stage at necropsy [3 to 24 h postpartum or d 20 of lactation]. Ewes were fed and housed individually in a temperature-controlled facility. At parturition, all lambs were removed and artificially reared until necropsy on d 20.6 +/- 0.9 of age. Ewes assigned to the treatment at d 20 of lactation were transitioned to a common diet meeting lactation requirements and were mechanically milked. From d 95 of gestation through parturition and d 20 of lactation, ewe BW and BCS were least (P <or= 0.01) in the RES treatment, intermediate in the CON treatment, and greatest in the HIH treatment. Ewes fed HSe had a greater (P <or= 0.05) BCS increase than those fed ASe during mid- and late gestation. During gestation, ewes in the HIH treatment had the greatest (P < 0.001) ADG and G:F, those in the CON treatment were intermediate, and those in the RES treatment were least, whereas ewes fed HSe had greater (P < 0.001) ADG and G:F than those fed ASe during midgestation. Ewe backfat and LM area on d 135 of gestation were least (P < 0.001) in the RES treatment, intermediate in the CON treatment, and greatest in the HIH treatment, with ewes fed HSe having greater (P <or= 0.03) backfat than those fed ASe. During the first 20 d of lactation, ewes fed the RES diet had greater (P < 0.09) G:F than those fed the CON and HIH diets. Physiological stage had no effect on ewe omental and mesenteric fat or perirenal fat weights, although both were greater (P < 0.001) for ewes fed the HIH diet than for those fed the RES and CON diets. At birth, lambs born to ewes in the RES group weighed less and had decreased curved crown rump lengths (P = 0.08) compared with those born to ewes in the CON and HIH groups, and lambs from ewes in the ASe-RES treatment were lighter (P < 0.08) than those from ewes in the HSe-RES, ASe-CON, and ASe-HIH treatments. Lambs from dams in the RES group had less (P < 0.05) BW from d 7 to 19 and decreased (P < 0.07) overall ADG compared with lambs from dams in the CON and HIH groups. Additionally, lambs from dams in the RES group had less (P <or= 0.08) perirenal fat than their counterparts, and lambs from dams in the HIH group had greater (P = 0.01) omental and mesenteric fat than lambs from dams in the RES group. Postpartum serum Se of ewes and lambs (birth and d 19) was increased (P < 0.001) by HSe feeding during gestation. Results indicate that BW differences in pregnant ewes attributable to nutritional plane are accompanied by changes in body composition and offspring BW, both of which may be affected by Se supply.