Effects of selenium supply and dietary restriction on maternal and fetal body weight, visceral organ mass and cellularity estimates, and jejunal vascularity in pregnant ewe lambs

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.     

Maternal selenium supplementation and timing of nutrient restriction in pregnant sheep: Impacts on nutrient availability to the fetus

To determine the effects of maternal Se intake and plane of nutrition during mid or late gestation or both on AA concentrations and metabolite concentrations in the dam and fetus, pregnant ewe lambs (n = 64) were assigned to 1 of 8 treatments arranged in a 2 × 2 × 2 factorial array: Se level [initiated at breeding; adequate (ASe; 3.05 μg/kg of BW) or high (HSe; 70.4 μg/kg of BW)] and nutritional level [100% (control; CON) or 60% (restricted; RES) of NRC recommendations] fed at different times of gestation [d 50 to 90 (mid) or d 91 to 132 (late)]. A blood sample was obtained from each ewe and fetus on d 132 of gestation and used to measure circulating concentrations of glucose, NEFA, blood urea N, and AA. The late RES ewes and their fetuses had less (P ≤ 0.03) circulating glucose compared with late CON ewes and fetuses at d 132; however, no effect (P ≥ 0.14) of diet on the fetal:maternal glucose concentration ratio was observed. Late RES ewes had a smaller (P = 0.01) fetal:maternal NEFA ratio compared with late CON ewes. Ewes fed ASe had a greater (P = 0.01) fetal:maternal blood urea N ratio compared with HSe ewes. Fetal:maternal ratios of total circulating AA, total essential AA, and total nonessential AA were each affected (P ≤ 0.03) by the combination of Se treatment and late gestation nutritional level.     

Impacts of maternal selenium and nutritional level on growth, adiposity, and glucose tolerance in female offspring in sheep

To examine effects of maternal nutrition and Se intake on adiposity and insulin sensitivity in female offspring, treatments were imposed during gestation on 82 pregnant primiparous Rambouillet ewe lambs (52.2 ± 0.8 kg) allotted randomly to 1 of 6 treatments in a 2 × 3 factorial arrangement. Factors were adequate (9.5 μg Se·kg BW(-1)·d(-1); ASe) or high (81.8 μg Se·kg BW(-1)·d(-1); HSe) levels of dietary Se (Se-enriched yeast) and maternal nutritional intake (100% of metabolizable energy [ME] requirement [MOD], 60% of MOD [LOW], and 140% of MOD [HIGH]). Selenium treatments were initiated at breeding and global nutritional treatments at day 50 of gestation. At parturition, lambs were removed from ewes before nursing and managed similarly. Glucose tolerance tests were performed at 107 and 148 d of age. Necropsies were performed at 180 d of age. Although there was no effect of Se on maternal body condition or weight during gestation, both maternal nutritional intake and selenium treatment influenced (P ≤ 0.04) offspring growth and response to a glucose tolerance test. Female lambs from HSe ewes were heavier (P = 0.04) at birth. There were nutritional intake and Se interactions (P ≤ 0.05) on the growth rate of the lambs and their insulin response to a glucose bolus at 2 different times during growth. By 180 d, ewe lambs from HSe ewes had more (P ≤ 0.07) internal fat stores than lambs from ASe ewes. It appears that both maternal nutritional level and Se intake can influence insulin sensitivity, and maternal Se intake alone can enhance fat deposition in female offspring.     

Nutritional plane and selenium supply during gestation affect yield and nutrient composition of colostrum and milk in primiparous ewes

The objectives were to investigate effects of nutritional plane and Se supply during gestation on yield and nutrient composition of colostrum and milk in first parity ewes. Rambouillet ewe lambs (n = 84, age = 240 ± 17 d, BW = 52.1 ± 6.2 kg) were allocated to 6 treatments in a 2 × 3 factorial array. Factors included Se [adequate Se (ASe, 11.5 μg/kg of BW) or high Se (HSe, 77.0 μg/kg of BW)] initiated at breeding, and nutritional plane [60 (RES), 100 (CON), or 140% (HIH) of requirements] initiated at d 40 of gestation. Ewes were fed individually from d 40, and lambs were removed at parturition. Colostrum was milked from all ewes at 3 h postpartum, and one-half of the ewes (n = 42) were transitioned to a common diet meeting lactation requirements and mechanically milked for 20 d. Colostrum yield was greater (P = 0.02) for HSe ewes than ASe, whereas CON had greater (P < 0.05) colostrum yield than RES and HIH. Colostrum Se (%) was greater (P < 0.01) for HSe than ASe. Colostrum from ewes fed HSe had less (P = 0.03) butterfat (%), but greater (P ≤ 0.05) total butterfat, solids-not-fat, lactose, protein, milk urea N, and Se than ASe. Colostrum from HIH ewes had greater (P ≤ 0.02) solids-not-fat (%) than RES, whereas RES had greater (P ≤ 0.04) butterfat (%) than CON and HIH. Colostrum from ewes fed the CON diet had greater (P = 0.01) total butterfat than HIH. Total solids-not-fat, lactose, and protein were greater (P < 0.05) in colostrum from CON than RES and HIH. Ewes fed HSe had greater (P < 0.01) milk yield (g/d and mL/d) than ASe, and CON and HIH had greater (P < 0.01) yield than RES. Milk protein (%) was greater (P ≤ 0.01) in RES compared with CON or HIH. Ewes fed HSe had greater (P < 0.01) milk Se (μg/g and mg/d) than ASe on each sampling day. Milk from CON and HIH ewes had greater (P < 0.01) total solids-not-fat, lactose, protein, and milk urea N than RES. Total Se was greater (P = 0.02) in milk from ewes fed the CON diet compared with RES. Somatic cell count and total somatic cells were greater (P ≤ 0.05) in milk from CON than RES. A cubic effect of day (P ≥ 0.01) was observed for milk yield (g and mL). Butterfat, solids-not-fat, lactose, milk urea N, and Se concentration responded quadratically (P ≤ 0.01) to day. Protein (%), total butterfat, and total Se, and somatic cells (cells/mL and cells/d) decreased linearly (P < 0.01) with day. Results indicate that gestational nutrition affects colostrum and milk yield and nutrient content, even when lactational nutrient requirements are met.     

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

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 per 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 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 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.     

Effects of maternal nutrition and stage of gestation on body weight, visceral organ mass, and indices of jejunal cellularity, proliferation, and vascularity in pregnant ewe lambs

Peripubertal ewe lambs (44.3 +/- 1.1 kg of initial BW) were used in a 2 x 3 factorial design to test the effects of plane of nutrition (diet) and stage of gestation on maternal visceral tissue mass, intestinal cellularity, crypt cell proliferation, and jejunal mucosal vascularity. Singleton pregnancies to a single sire were established by embryo transfer, and thereafter ewes were offered a control (Control) or high (High) amount of a complete diet (2.84 Mcal/kg and 15.9% CP; DM basis) to promote slow or rapid maternal growth rates. After d 90 of gestation, feed intake of the Control group was adjusted weekly to maintain BCS and meet the increasing nutrient demands of the gravid uterus. Ewes were slaughtered at 50 d (n = 6 Control; n = 5 High), 90 d (n = 8 Control; n = 6 High), or 130 d (n = 8 Control; n = 6 High) of gestation. Ewes were eviscerated and masses of individual organs were recorded. The jejunum was sampled and processed for subsequent analyses. Final ewe BW for Control-fed ewes was similar at d 50 and 90 and increased (P = 0.10) from d 90 to 130 (46.0, 48.9, and 58.2 +/- 1.6 kg, respectively), whereas final BW increased (P 相似文献   

Maternal nutrition during pregnancy influences offspring wool production and wool follicle development

The effects of maternal nutrition on offspring wool production (quality and quantity) were evaluated. Primiparous Rambouillet ewes (n = 84) were randomly allocated to 1 of 6 treatments in a 2 × 3 factorial design. Selenium treatment [adequate Se (ASe, 9.5 μg/kg of BW) vs. high Se (HSe, 81.8 μg/kg of BW)] was initiated at breeding, and maternal nutritional intake [control (CON, 100% of requirements) vs. restricted (60% of CON) vs. overfed (140% of CON)] was initiated at d 50 of gestation. Lamb birth weight was recorded at delivery, and all lambs were placed on the same diet immediately after birth to determine the effects of prenatal nutrition on postnatal wool production and follicle development. At 180 ± 2.2 d of age, lambs were necropsied and pelt weights were recorded. Wool samples were collected from the side and britch areas, whereas skin samples were collected from the side of each lamb only. Although Se status did not influence side staple length in males, female lambs born from ewes on the ASe treatment had a shorter staple length (P < 0.05) when compared with females from ewes on the HSe treatment. Maternal nutritional intake and Se status did not influence (P ≥ 0.23) wool characteristics on the britch. However, at the britch, wool from female lambs had a reduced comfort factor (P = 0.01) and a greater (P = 0.02) fiber diameter compared with wool from male lambs. Maternal Se supplementation, maternal nutritional plane, sex of the offspring, or their interactions had no effect (P > 0.13) on primary (29.10 ± 1.40/100 μm(2)) and secondary (529.84 ± 21.57/100 μm(2)) wool follicle numbers. Lambs from ASe ewes had a greater (P = 0.03) secondary:primary wool follicle ratio compared with lambs from HSe ewes (20.93 vs. 18.01 ± 1.00). Despite similar postnatal diets, wool quality was affected by maternal Se status and the maternal nutritional plane.     

Effects of selenium supply and dietary restriction on maternal and fetal metabolic hormones in pregnant ewe lambs

The objective of these studies was to evaluate the effects of dietary restriction and Se on maternal and fetal metabolic hormones. In Exp. 1, pregnant ewe lambs (n = 32; BW = 45.6 +/- 2.3 kg) were allotted randomly to 1 of 4 treatments. Diets contained (DM basis) either no added Se (control), or supranutritional Se added as high-Se wheat at 3.0 mg/kg (Se-wheat), or sodium selenate at 3 (Se3) and 15 (Se15) mg/kg of Se. Diets (DM basis) were similar in CP (15.5%) and ME (2.68 Mcal/kg). Treatments were initiated at 50 +/- 5 d of gestation. The control, Se-wheat, Se3, and Se15 treatments provided 2.5, 75, 75, and 375 microg/kg of BW of Se, respectively. Ewe jugular blood samples were collected at 50, 64, 78, 92, 106, 120, and 134 d of gestation. Fetal serum samples were collected at necropsy on d 134. In Exp. 2, pregnant ewe lambs (n = 36; BW 53.8 +/- 1.3 kg) were allotted randomly to treatments in a 2 x 2 factorial arrangement. Factors were nutrition (control, 100% of requirements vs. restricted nutrition, 60% of control) and dietary Se (adequate Se, 6 microg/kg of BW vs. high Se, 80 microg/kg of BW). Selenium treatments were initiated 21 d before breeding, and nutritional treatments were initiated on d 64 of gestation. Diets were 16% CP and 2.12 Mcal/kg of ME (DM basis). Blood samples were collected from the ewes at 62, 76, 90, 104, 118, 132, and 135 d of gestation. Fetal blood was collected at necropsy on d 135. In Exp.1, dietary Se source and concentration had no effect (P > 0.17) on maternal and fetal serum IGF-I, triiodothyronine (T(3)), or thyroxine (T(4)) concentrations. Selenium supplementation increased (P = 0.06) the T(4):T(3) ratio vs. controls. In Exp. 2, dietary Se had no impact (P > 0.33) on main effect means for maternal and fetal serum IGF-I, T(3), or T(4) concentrations from d 62 to 132; however, at d 135, high-Se ewes had lower (P = 0.01) serum T(4) concentrations than adequate-Se ewes. A nutrition by Se interaction (P = 0.06) was detected for the T(4):T(3) ratios; ewes fed restricted and adequate-Se diets had greater (P = 0.10) T(4):T(3) ratios compared with the other treatments. Nutrient-restricted ewes had lower (P < 0.05) serum IGF-I, T(3), and T(4) concentrations. Fetal serum IGF-I concentrations were lower (P = 0.01) in restricted-vs. control-fed ewes; however, fetal T(3) and T(4) concentrations were unaffected (P > 0.13) by dietary Se or maternal plane of nutrition. These data indicate that dietary Se may alter maternal T(4):T(3) ratios. In addition, nutrient restriction during gestation reduces maternal IGF-I, T(3), and T(4) and fetal IGF-I concentrations.     

Effects of maternal selenium supply and plane of nutrition during gestation on passive transfer of immunity and health in neonatal lambs

To investigate the influence of maternal Se supply and plane of nutrition on lamb morbidity, mortality, and passive transfer of IgG, pregnant ewe lambs were used in 2 experiments with 2 × 3 factorial treatment arrangements. Supplementation of Se began at breeding and was either adequate Se (ASe, 9.5 μg/kg of BW) or high Se (HSe, 81.8 μg/kg of BW) in Exp. 1 or ASe (11.5 μg/kg of BW) or HSe (77.0 μg/kg of BW) in Exp. 2. On d 50 or 40 of gestation for Exp. 1 or 2, respectively, ewes were assigned randomly to 1 of 3 nutritional planes: 60% (RES), 100% (control, CON), or 140% (HI) of NRC requirements. This resulted in the following treatments: ASe-RES, ASe-CON, ASe-HI, HSe-RES, HSe-CON, and HSe-HI. Upon parturition, lambs were separated from their dams and serum samples obtained. Lambs were fed artificial colostrum for the first 20 h and then placed on milk replacer and grain pellets until completion of the study (Exp. 1, 57 d; Exp. 2, 21 d). Twenty-four hours after parturition, lamb serum samples were collected for IgG analysis. All lambs were reared similarly and morbidity and mortality assessed. Main effects were considered significant when P ≤ 0.05. In Exp. 1, there was a Se × plane of nutrition interaction (P ≤ 0.01) for lamb morbidity from birth to weaning and for 24-h IgG concentration. Lambs from ASe-RES and HSe-HI ewes were treated more frequently (P < 0.01) for respiratory and gastrointestinal disease, and lambs from HSe-HI ewes had the smallest (P < 0.01) 24-h serum IgG concentration. In Exp. 1, lambs from HI ewes also had the greatest (P < 0.01) mortality rates from birth to weaning compared with lambs from CON and RES ewes. In Exp. 2, there was an effect (P < 0.01) of maternal plane of nutrition with lambs from RES ewes having increased 24-h IgG compared with lambs from CON and HI ewes. There was no effect of maternal Se supplementation on lamb 24-h IgG in Exp. 2; however, there was a Se × plane of nutrition interaction (P < 0.01) for morbidity. From birth to 21 d of age, lambs from ASe-CON ewes had fewer (P < 0.01) treatment days compared with lambs from any of the other treatment groups. There also tended (P = 0.08) to be an effect of maternal Se supplementation on lamb mortality with increased mortality observed in lambs from HSe ewes. Results from the studies show a restricted maternal plane of nutrition can increase lamb serum IgG concentration. Selenium results were not consistent between the 2 experiments and may be due to differences in maternal Se.     

The effect of dietary restriction, pregnancy, and fetal type in different ewe types on fetal weight, maternal body weight, and visceral organ mass in ewes

Our objectives were to evaluate maternal body changes in response to dietary restriction or the increased nutrient requirement of fetal growth. In Exp. 1, 28 mature crossbred ewes (61.6 +/- 1.8 kg initial BW) were fed a pelleted forage-based diet to evaluate effects of pregnancy and nutrient restriction on visceral organ mass. Treatments were arranged in 2 x 3 factorially, with dietary restriction (60% restriction vs. 100% maintenance) and reproductive status (nonpregnant [NP], d 90 or d 130 of gestation) as main effects. Dietary treatments were begun at d 50 of gestation, and restricted ewes remained at 60% of maintenance throughout the experiment. Nonpregnant and d-90 ewes were fed dietary treatments for 40 d and slaughtered. The d-130 ewes were fed dietary treatments for 80 d and then slaughtered. In Exp. 2, four Romanov ewes were naturally mated (Romanov fetus and Romanov dam; R/ R), and two Romanov embryos were transferred to each of four Columbia recipients (Romanov embryos and Columbia recipient; R/C). Three Columbia ewes were naturally mated (Columbia fetus and Columbia recipient; C/C). In both experiments, maternal organ weights were reported as fresh weight (grams), scaled to empty body weight (EBW; grams per kilogram) and maternal body weight (MBW; grams per kilogram). In Exp. 1, ewe EBW and fetal mass were decreased (P < 0.02) with restriction compared with maintenance. Dietary restriction decreased liver mass (16.7 vs. 14.5 g/kg EBW or 18.8 vs. 16.4 g/kg MBW; P < 0.01), but dietary restriction did not affect total digestive tract mass. In Exp. 2, ewe BW was less for the R/R compared with R/C and C/C (44.8 vs. 110.4 and 98.1 +/- 7.9 kg, respectively; P < 0.01). Fetal weight at d 130 was less for the R/R than for R/C and C/C (2.2 vs. 3.3 and 4.7 +/- 0.3 kg, respectively; P < 0.01) when measured as individual fetuses; however, when measured as total fetal mass carried in each ewe, there was no effect of ewe type. These data suggest that the gastrointestinal tract, along with other maternal organs, responds to both level of dietary intake and nutrient requirements for gestation, and that fetal weight is decreased as a result of a 40% decrease in nutrients offered.     

Effects of level and source of dietary selenium on maternal and fetal body weight, visceral organ mass, cellularity estimates, and jejunal vascularity in pregnant ewe lambs

Pregnant Targhee ewe lambs (n = 32; BW = 45.6 +/- 2.2 kg) were allotted randomly to 1 of 4 treatments in a completely randomized design to examine the effects of level and source of dietary Se on maternal and fetal visceral organ mass, cellularity estimates, and maternal jejunal crypt cell proliferation and vascularity. Diets contained (DM basis) either no added Se (control) or supranutritional Se from high-Se wheat at 3.0 ppm Se (SW) or from sodium selenate at 3 (S3) or 15 (S15) ppm Se. Diets were similar in CP (15.5%) and ME (2.68 Mcal/kg of DM) and were fed to meet or exceed requirements. Treatments were initiated at 50 +/- 5 d of gestation. The control, SW, S3, and S15 treatment diets provided 2.5, 75, 75, and 375 microg of Se/kg of BW, respectively. On d 134 +/- 10 of gestation, ewes were necropsied, and tissues were harvested. Contrasts, including control vs. Se treatments (SW, S3, and S15), SW vs. S3, and S3 vs. S15, were used to evaluate differences among Se levels and sources. There were no differences in ewe initial and final BW. Full viscera and liver mass (g/kg of empty BW and g/kg of maternal BW) and maternal liver protein concentration (mg/g) and content (g) were greater (P < 0.04) in Se-treated compared with control ewes. Maternal liver protein concentration was greater (P = 0.01) in SW vs. S3 ewes, and content was greater (P = 0.01) in S15 compared with S3 ewes. Maternal jejunal mucosal DNA concentration (mg/g) was greater (P = 0.08) in SW compared with S3 ewes. Total number of proliferating cells in maternal jejunal mucosa was greater (P = 0.02) in Se-fed compared with control ewes. Capillary number density within maternal jejunal tissue was greater (P = 0.08) in S3 compared with SW ewes. Selenium treatment resulted in reduced fetal heart girth (P = 0.08). Fetal kidney RNA (P = 0.04) and protein concentrations (mg/g; P = 0.03) were greater in Se-treated compared with control ewes. These results indicate that supranutritional dietary Se increases cell numbers in maternal jejunal mucosa through increased crypt cell proliferation. No indications of toxicity were observed in any of the Se treatments.     

Winter-feeding systems for gestating sheep I. Effects on pre- and postpartum ewe performance and lamb progeny preweaning performance

Mature pregnant crossbred ewes (n = 90) were used in a randomized complete block design and assigned to 1 of 3 winter-feeding systems differing in primary feed source: haylage (HL), limit-fed corn (CN), or limit-fed dried distillers grains (DDGS). Effects of these winter-feeding strategies on ewe and lamb performance were determined. Diets were formulated to meet or exceed NRC (1985) nutrient requirements during gestation and were fed from about d 60 of gestation until parturition. All ewes were fed a common diet postpartum. Every 2 wk during gestation, BW and BCS were collected and diets were adjusted to maintain similar BW gain for ewes fed CN and DDGS vs. HL. At 80 and 122 d of gestation, jugular blood samples were collected at 0, 3, 6, and 9 h postfeeding to measure plasma glucose, insulin, NEFA, and blood urea nitrogen concentrations. At birth, 6 lambs per treatment were killed to measure body composition. At 28 ± 2 d postpartum, milk yield was measured. Lambs were weaned at 61 ± 4 d of age. During mid gestation (d 60 to 115), BW gain of ewes was similar among treatments; however, at d 115 of gestation ewes fed HL had a smaller (P = 0.04) BCS than ewes fed DDGS or CN. Plasma glucose concentrations were greater (P ≤ 0.004) in ewes fed CN than in those fed HL or DDGS just before feeding on d 80 and 122 of gestation, whereas ewes fed DDGS vs. CN or HL had greater (P ≤ 0.04) plasma insulin concentrations at 3 h postfeeding. At parturition, ewe BW was greatest for DDGS, least for HL, and intermediate for CN (P ≤ 0.003). Ewes fed CN and DDGS had greater BCS at parturition than those fed HL, but by weaning, ewes fed DDGS had greater BCS (P ≤ 0.05) than those fed CN or HL. Birth BW tended (P = 0.09) to be heavier for lambs from ewes fed CN and DDGS than from those fed HL prepartum, but there was no difference (P = 0.19) due to ewe gestation diet on lamb BW at weaning. At birth, lamb muscle, bone, organ, and fat measures were not affected (P > 0.13) by treatment. Ewe milk production and lamb preweaning ADG were also similar (P > 0.44) among treatments. Prepartum dam winter feed source did not have detrimental effects on pre- or postpartum ewe performance, but altered prepartum maternal nutrient supply during gestation, which affected birth weight but not preweaning growth or mortality.     

Effects of gestational plane of nutrition and selenium supplementation on mammary development and colostrum quality in pregnant ewe lambs

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.     

Mammary gland growth and vascularity at parturition and during lactation in primiparous ewes fed differing levels of selenium and nutritional plane during gestation

Background

Objectives were to examine the effects of selenium (Se) supply and maternal nutritional plane during gestation on mammary gland growth, cellular proliferation, and vascularity at parturition and d 20 of lactation. Rambouillet primiparous ewes (n = 84) were allocated to treatments in a 2 x 3 factorial. Factors were dietary Se (adequate Se [ASe, 11.5 μg/kg BW] or high Se [HSe, 77.0 μg/kg BW]) and nutritional plane (60% [RES], 100% [CON], or 140% [EXC]). At parturition, lambs were removed and 42 ewes (7/treatment) were necropsied. Remaining ewes were fed a common diet meeting requirements for lactation and mechanically milked twice daily until necropsy on d 20. At both necropsy periods, mammary glands were dissected and tissues harvested. Samples were analyzed for RNA, DNA, and protein content, cell proliferation, and vascularity. Where interactions were present (P ≤ 0.05), least squares means from the highest-order interaction are presented.

Results

Final body weight of ewes was least (P ≤ 0.002) in RES, intermediate for CON, and greatest for EXC, regardless of stage of the ewe at necropsy (parturition or d 20 of lactation). In ewes necropsied at parturition, mammary glands were heavier (P = 0.02) in EXC compared to RES, with CON intermediate. Concentration of RNA (mg/g) was decreased (P = 0.01) in EXC compared to CON at parturition. There was a tendency (P = 0.07) for a Se by nutrition interaction in percentage of cells proliferating where ASe-EXC ewes had greater (P ≤ 0.02) number of proliferating cells then all other treatments. Mammary vascular area tended (P = 0.08) to be affected by a Se by nutrition interaction where ASe-CON had less (P = 0.007) vascular area than HSe-CON ewes. In ewes necropsied at d 20 of lactation, the number of alveoli per area was decreased (P ≤ 0.05) in RES compared to CON and EXC-fed ewes.

Conclusions

Results of this study indicate that proper maternal nutritional plane during gestation is important for mammary gland development, even out to d 20 of lactation.     

Winter grazing system and supplementation during late gestation influence performance of beef cows and steer progeny

A 2 x 2 factorial study evaluated effects of cow wintering system and last trimester CP supplementation on performance of beef cows and steer progeny over a 3-yr period. Pregnant composite cows (Red Angus x Simmental) grazed winter range (WR; n = 4/yr) or corn residue (CR; n = 4/yr) during winter and within grazing treatment received 0.45 kg/d (DM) 28% CP cubes (PS; n = 4/yr) or no supplement (NS; n = 4/yr). Offspring steer calves entered the feedlot 14 d postweaning and were slaughtered 222 d later. Precalving BW was greater (P = 0.02) for PS than NS cows grazing WR, whereas precalving BCS was greater (P < 0.001) for cows grazing CR compared with WR. Calf birth BW was greater (P = 0.02) for CR than WR and tended to be greater (P = 0.11) for PS than NS cows. Prebreeding BW and BCS were greater (P 0.32) by PS. Calf weaning BW was less (P = 0.01) for calves from NS cows grazing WR compared with all other treatments. Pregnancy rate was unaffected by treatment (P > 0.39). Steer ADG, 12th-rib fat, yield grade, and LM area (P > 0.10) were similar among all treatments. However, final BW and HCW (P = 0.02) were greater for steers from PS-WR than NS-WR cows. Compared with steers from NS cows, steers from PS cows had greater marbling scores (P = 0.004) and a greater (P = 0.04) proportion graded USDA Choice or greater. Protein supplementation of dams increased the value of calves at weaning (P = 0.03) and of steers at slaughter regardless of winter grazing treatment (P = 0.005). Calf birth and weaning BW were increased by grazing CR during the winter. Calf weaning BW was increased by PS of the dam if the dam grazed WR. Compared with steers from NS cows, steer progeny from PS cows had a greater quality grade with no (P = 0.26) effect on yield grade. These data support a late gestation dam nutrition effect on calf production via fetal programming.     

Winter-feeding systems for gestating sheep II. Effects on feedlot performance, glucose tolerance, and carcass composition of lamb progeny

Mature pregnant crossbred ewes (n = 90) were used in a randomized complete block design experiment and were assigned to 1 of 3 winter-feeding systems differing in primary feed source: haylage (HL), limit-fed corn (CN), or limit-fed dried distillers grains (DDGS). Effects of these winter-feeding strategies on postweaning progeny performance were determined. Lamb progeny (n = 96) were weaned at 61 ± 4 d of age and fed a common high-concentrate diet. Lambs were assigned to feedlot pen (n = 18) based on dam mid-gestation pen. Growth rate, DMI, and ADG were determined for the first 40 d of the finishing period. At 96 ± 4 d of age, 1 wether lamb was randomly selected from each pen (n = 18) for a glucose tolerance test. The experiment was terminated, and lambs were slaughtered individually when they were determined to have achieved 0.6-cm 12th-rib fat thickness. After a 24-h chill, carcass data were collected and a 2.54-cm chop was removed from each lamb from the LM posterior to the 12th rib for ether extract analysis. Additional carcass measurements of bone, muscle, and fat from the shoulder, rack, loin, and leg were collected on 35 carcasses. At weaning, lamb BW was not different among treatments, whereas final BW tended to be greater (P = 0.09) for lambs from ewes fed DDGS and CN during gestation than from those fed HL. Overall lamb growth rate from birth to slaughter was not different among treatments. Lambs from ewes fed DDGS vs. CN or HL tended to have a greater initial insulin response (P = 0.09). Dressing percent was less (P = 0.04) in lambs from ewes fed DDGS, but no difference (P = 0.16) was detected in HCW among treatments. As expected, 12th rib fat thickness was similar among treatments, whereas LM area was largest to smallest (P = 0.05) in lambs from ewes fed CN, HL, and DDGS, respectively. Proportion of internal fat tended to be greatest to smallest (P = 0.06) in lambs from ewes fed DDGS, CN, and HL, respectively. Calculated boneless trimmed retail cuts percentage was less (P = 0.04) in lambs from ewes fed DDGS than CN or HL. Loin muscle weight as a percentage of wholesale cut tended (P = 0.10) to be greater in lambs from ewes fed CN and HL than DDGS, whereas other muscle, bone, and fat weights and proportions were similar (P > 0.24) among treatments. Prepartum diet during mid to late gestation of ewes altered postnatal fat and muscle deposition and may be associated with alterations in insulin sensitivity of progeny.     

Effects of nutritional level and biological type on gonadotropin-releasing hormone-induced luteinizing hormone release and plasma progesterone, estrone and estradiol concentrations in pre- and post-partum beef heifers

Forty-six beef heifers (16 to 23 mo) of two biological types (small = Red Poll-sired, large = Charolais-sired) were individually fed from d 90 of gestation through parturition to evaluate the effects of nutritional restriction on plasma LH and steroid hormone concentrations. Heifers were allotted to one of two nutritional treatments to achieve a BW reduction (loss, fed at 1% of BW/d) or to maintain initial BW (maintenance, fed 1.5% of BW/d) to parturition. Gonadotropin-releasing hormone (100 micrograms) was injected i.m. three times during gestation (d 130; d 200; d 270) and twice after parturition (d 1 to 14; d 23 to 36). Blood samples were collected at 20-min intervals after GnRH for 4 h. Maternal BW change from d 90 to parturition differed (P less than .01) between loss and maintenance heifers. Mean plasma progesterone concentrations were greater (P less than .05) at d 130 and 270 of gestation in small than in large heifers and were greater (P less than .01) at d 23 to 36 postpartum in maintenance than in loss heifers. Mean concentrations of estrone and estradiol were greater (P less than .05) in large than in small heifers at d 200 of gestation. Mean plasma LH concentrations following GnRH injection were greater (P less than .01) in loss than in maintenance heifers at 200 and 270 d of gestation. Metabolizable and retained energy were related inversely to LH release during mid and late gestation.(ABSTRACT TRUNCATED AT 250 WORDS)     

A regional evaluation of the effect of fiber type in gestation diets on sow reproductive performance

A cooperative regional research study using 194 sows, from which data were collected from 381 litters, was conducted at 3 research stations to determine the effects of added psyllium (a concentrated fiber source) or soybean hulls to gestation diets on reproductive performance of sows and preweaning performance of their pigs. Primiparous and multiparous sows were allotted to the 3 treatments of control (corn and soybean meal-based), 0.30% psyllium, or 20% soybean hulls. Sows fed the control and 0.30% psyllium diets were provided 1.82 kg/d, and sows fed the 20% soybean hulls diet were provided 2.0 kg/d to equalize ME, Lys, Ca, P, and vitamin and trace mineral intake. Treatments 1 to 3 had 130, 130, and 121 litters per treatment from 64, 64, and 63 sows, respectively. Gestating sows fed psyllium had a greater (P < 0.01 to 0.10) d 110 gestation, farrowing, weaning, and 17 d postpartum BW and gestation ADG compared with sows fed soybean hulls. Sows fed psyllium also had a greater (P < 0.10 and 0.08) d 110 gestation BW and gestation ADG than the control sows. Sows fed soybean hulls had a reduced (P < 0.06) farrowing BW compared with the control sows. Sows fed psyllium weaned lighter (P < 0.09) pigs than sows fed the control diet. Litter size was not affected (P > 0.10) by diet. Sows fed psyllium had a reduced (P < 0.03) feed intake compared with sows fed soybean hulls for d 5 to 7 postpartum, and sows fed the control diet were intermediate. Fecal scores (1 to 5 with 1 = dry and 5 = watery) were greater (P < 0.001) and DM content was less (P < 0.001 to 0.01) in the feces of sows fed soybean hulls compared with sows fed psyllium or the control diet on d 112 of gestation and d 4 postpartum. Fecal scores were greater (P < 0.10) and fecal DM content was less (P < 0.02) in sows fed psyllium compared with sows fed the control diet only on d 4 postpartum. In summary, sows fed soybean hulls during gestation had reduced BW compared with sows fed the control diets. In contrast, sows fed psyllium had an increased BW.     

Effect of dietary restriction, pregnancy, and fetal type on intestinal cellularity and vascularity in Columbia and Romanov ewes

The objectives of this study were to evaluate intestinal cellularity and vascularity in mature ewes in response to dietary restriction and pregnancy status and to quantify the response of these variables to increased nutrient demand of fetal growth. In Exp. 1, 28 mature Dorset x crossbred white-faced ewes (61.6+/-1.8 kg initial BW) were fed a pelleted, forage-based diet. Treatments were arranged in a 2 x 3 factorial, with dietary restriction (60% restriction vs. 100% maintenance for respective states of pregnancy) and pregnancy status (nonpregnant, NP; d 90 and 130) as main effects. Dietary treatments were initiated on d 50 of gestation and remained at 60 or 100% maintenance throughout the experiment. Nonpregnant ewes were fed dietary treatments for 40 d. In Exp. 2, four Romanov ewes were naturally serviced (Romanov fetus and Romanov dam; R/R); two Romanov embryos per recipient were transferred to four Columbia recipients (Romanov fetus and Columbia recipient; R/C), and three Columbia ewes were naturally serviced (Columbia fetus and Columbia dam; C/C). In Exp. 1, dietary restriction and pregnancy status interacted with regard to maternal jejunal DNA concentration (P < 0.01), with restricted ewes having a greater DNA concentration (mg/g; fresh basis) at d 130. Vascularity (percentage of total tissue area) in the jejunum was increased (P < 0.06) as a result of dietary restriction and pregnancy status. Total microvascular volume ofjejunal tissue was not altered by dietary restriction and increased (P < 0.01) at d 130 of pregnancy. In Exp. 2, R/R ewes had less (P < 0.09) DNA (g) in the jejunum compared with R/C and C/C ewes. Jejunal vascularity (%) was increased (P < 0.05) in R/R ewes compared with R/C or C/C ewes, whereas total jejunal microvascular volume remained unchanged. These data demonstrate intestinal vascular density responds to changes in diet and physiological state. In addition, pregnancy increased total jejunal microvascular volume.