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.     

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.     

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.     

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.     

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.     

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.     

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.     

Effects of dietary selenium supply and timing of nutrient restriction during gestation on maternal growth and body composition of pregnant adolescent ewes

The objectives were to examine effects of dietary Se supplementation and nutrient restriction during defined periods of gestation on maternal adaptations to pregnancy in primigravid sheep. Sixty-four pregnant Western Whiteface ewe lambs were assigned to treatments in a 2 x 4 factorial design. Treatments were dietary Se [adequate Se (ASe; 3.05 microg/kg of BW) vs. high Se (HSe; 70.4 microg/kg of BW)] fed as Se-enriched yeast, and plane of nutrition [control (C; 100% of NRC requirements) vs. restricted (R; 60% of NRC requirements]. Selenium treatments were fed throughout gestation. Plane of nutrition treatments were applied during mid (d 50 to 90) and late gestation (d 90 to 130), which resulted in 4 distinct plane of nutrition treatments [treatment: CC (control from d 50 to 130), RC (restricted from d 50 to 90, and control d 90 to 130), CR (control from d 50 to 90, and restricted from d 90 to 130), and RR (restricted from d 50 to 130)]. All of the pregnant ewes were necropsied on d 132 +/- 0.9 of gestation (length of gestation approximately 145 d). Nutrient restriction treatments decreased ewe ADG and G:F, as a result, RC and CR ewes had similar BW and maternal BW (MBW) at necropsy, whereas RR ewes were lighter than RC and CR ewes. From d 90 to 130, the HSe-CC ewes had greater ADG (Se x nutrition; P = 0.05) than did ASe-CC ewes, whereas ADG and G:F (Se x nutrition; P = 0.08) were less for HSe-RR ewes compared with ASe-RR ewes. The CR and RR treatments decreased total gravid uterus weight (P = 0.01) as well as fetal weight (P = 0.02) compared with RC and CC. High Se decreased total (g; P = 0.09) and relative heart mass (g/kg of MBW; P = 0.10), but increased total and relative mass of liver (P < or = 0.05) and perirenal fat (P < or = 0.06) compared with ASe. Total stomach complex mass was decreased (P < 0.01) by all the nutrient restriction treatments, but was reduced to a greater extent in CR and RR compared with RC. Total small intestine mass was similar between RC and CC ewes, but was markedly reduced (P < 0.01) in CR and RR ewes. The mass of the stomach complex and the small and large intestine relative to MBW was greater (P = 0.01) for RC than for CR ewes. Increased Se decreased jejunal DNA concentration (P = 0.07), total jejunal cell number (P = 0.03), and total proliferating jejunal cell number (P = 0.05) compared with ASe. These data indicate that increased dietary Se affected whole-body and organ growth of pregnant ewes, but the results differed depending on the plane of nutrition. In addition, the timing and duration of nutrient restriction relative to stage of pregnancy affected visceral organ mass in a markedly different fashion.     

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.     

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 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.     

Effects of nutrient restriction and melatonin supplementation on maternal and foetal hepatic and small intestinal energy utilization

To determine how nutrient restriction and melatonin supplementation influence ewe and foetal hepatic and small intestinal energy use, 32 primiparous ewes on d 50 of gestation were fed 60% (RES) or 100% (ADQ) of NRC recommendations with 0 (CON) or 5 mg/d (MEL) of dietary melatonin. On d 130 of gestation, small intestine and liver were weighed and collected. Data were analysed as a completely randomized design with a 2 × 2 factorial arrangement of treatments. Liver weight (g/kg EBW) decreased (p = 0.02) in RES ewes. Jejunum weight (g/kg BW) increased (interaction p = 0.04) in ADQ‐MEL ewes compared with all other treatments. Total in vitro O₂ consumption (mol/min/tissue) and total citrate synthase activity (mol/min/tissue and mol/min/kg EBW) in liver decreased (p ≤ 0.03) in RES ewes. Oxygen consumption (mol/min/kg EBW) increased (interaction p = 0.02) in jejunum of ADQ‐CON versus RES‐MEL and ADQ‐CON. Citrate synthase activity (mol/min/kg of EBW) increased (interaction p = 0.03) in jejunum of ADQ‐MEL compared with RES‐MEL and ADQ‐CON. Foetal liver weight (g/kg BW) decreased (p = 0.02) in RES versus ADQ. Foetal small intestine weight (g/kg BW) decreased (interaction p = 0.05) in RES‐MEL versus ADQ‐MEL. Total O₂ consumption (mol/min/tissue) and total citrate synthase activity (mol/min/kg of BW) in foetal liver decreased (p ≤ 0.05) in RES versus ADQ. Foetal small intestinal O₂ consumption (mol/min/kg of BW) was greater (interaction p = 0.03) in RES‐CON and ADQ‐MEL than RES‐MEL and ADQ‐CON. Maternal nutrient restriction had a greater effect than melatonin supplementation on liver and jejunum mass and energy utilization in dams and foetuses. Because intestinal mass and energy utilization were more responsive to melatonin supplementation in ewes fed adequate nutrition compared with restricted ewes, melatonin may have limited use as a therapeutic supplement to help overcome potential negative effects of nutrient restriction.     

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   

Tolerance of inorganic selenium by range-type ewes during gestation and lactation

The objectives of this 72-wk study were to evaluate and compare the effects of 6 dietary levels of inorganic Se on serum, whole blood, wool, and tissue Se concentrations and to determine the maximum tolerable level of Se for mature ewes during lamb production. Forty-one, 4-yr-old, range-type ewes (57.4 +/- 5.7 kg) were used in a completely randomized design with 6 dietary treatments. Sodium selenite was added to a corn and soybean meal-based diet to provide 0.2 (control), 4, 8, 12, 16, or 20 mg of dietary Se/kg to ewes during lamb production. Serum Se and ewe BW were measured at 4-wk intervals; whole blood Se and wool Se were measured every 12 wk; and samples of brain, diaphragm, heart, hoof, kidney, liver, and psoas major were collected at the termination of the experiment. Dietary Se did not affect ewe BW during the study (P = 0.69), and there was no treatment x time interaction. Serum Se increased linearly as dietary Se level increased (P < 0.001) and responded cubically (P = 0.02) over time. Selenium in whole blood increased linearly (P < 0.001) as supplemental Se increased. Wool Se increased linearly (P < 0.001) as dietary Se increased, and the response over time was quadratic (P < 0.001). Brain, diaphragm, heart, and psoas major Se increased (P < 0.05) linearly as dietary Se increased, liver Se responded quadratically (P < 0.05), and hoof and kidney Se increased cubicically (P < 0.05) as supplemental Se increased. In general, serum, whole blood, and tissue Se concentrations of ewes receiving 12, 16, or 20 mg of dietary Se/kg were greater (P < 0.05) than those of controls and ewes receiving less dietary Se. Although they were elevated in ewes receiving increased dietary Se, at no time did serum, whole blood, or wool Se concentrations reach levels previously reported as toxic, nor were clinical signs of Se toxicosis observed. Histopathological evaluation of liver, kidney, diaphragm, heart, and psoas major did not reveal evidence of Se toxicosis in ewes at any dietary Se level. Ewes under our experimental conditions and during the stresses of production were able to tolerate up to 20 mg of dietary Se/kg as sodium selenite for 72 wk. These findings suggest that the maximum tolerable level of inorganic Se for sheep is much greater than 2 mg/kg as was suggested previously. Experiments of longer duration and utilizing greater dietary Se concentrations are necessary to clearly define the maximum tolerable level.     

Evaluation of biochemical evidence of congenital nutritional myopathy in two-week prepartum fetuses from selenium-deficient ewes

Muscle damage attributable to selenium (Se)/vitamin E deficiencies is known to develop at birth or later in lambs. The purpose of this study was to determine whether and when muscle damage develops in utero. Thirty pregnant ewes maintained on Se-deficient forages from birth were allotted to 3 equal groups. Half of each group was given a single IM injection of 0.056 mg of Se/kg of body weight, 1 month before parturition. At 3 weeks before parturition, cesarean section-derived fetuses from Se-deficient ewes did not have evidence of muscle damage. At 2 weeks before parturition, fetuses from Se-deficient ewes had biochemical evidence of congenital nutritional myopathy, as evidenced by low blood Se concentration (P less than 0.05) and by increased plasma creatinine kinase (P less than 0.001) and lactate dehydrogenase (P less than 0.01) activities, compared with fetuses from Se-treated ewes. Thus, for optimal protection of fetuses and newborn lambs in Se-deficient areas, Se should be administered to ewes at least 1 month before parturition.     

Effects of supplementary selenium source on the performance and blood measurements in beef cows and their calves

On December 2, 1999, 120 pregnant cows were weighed, their body condition scored, and then sorted into six groups of 20 stratified by BCS, BW, breed, and age. Groups were assigned randomly to six, 5.1-ha dormant common bermudagrass (Cynodon dactylon [L.] Pers.) pastures for 2 yr to determine the effects of supplemental Se and its source on performance and blood measurements. During the winter, each group of cows had ad libitum access to bermudagrass/dallisgrass (Paspalum dilatatum Poir.) hay plus they were allowed limited access (1 to 4 d/wk) to a 2.4-ha winter-annual paddock planted in half the pasture. Treatments were assigned randomly to pastures (two pastures per treatment), and cows had ad libitum access to one of three free-choice minerals: 1) no supplemental Se, 2) 26 mg of supplemental Se from sodium selenite/kg, and 3) 26 mg of supplemental Se from seleno-yeast/kg (designed intake = 113 g/cow daily). Data were analyzed using a mixed model; year was the random effect and treatment was the fixed effect. Selenium supplementation or its source had no effect (P > or = 0.19) on cow BW, BCS, conception rate, postpartum interval, or hay DMI. Birth date, birth weight, BW, total BW gain, mortality, and ADG of calves were not affected (P > 0.20) by Se or its source. Whole blood Se concentrations and glutathione peroxidase (GSH-Px) activity at the beginning of the trial did not differ (P > or = 0.17) between cows receiving no Se and cows supplemented with Se or between Se sources. At the beginning of the calving and breeding seasons, cows supplemented with Se had greater (P < 0.01) whole blood Se concentrations and GSH-Px activities than cows receiving no supplemental Se; cows fed selenoyeast had greater (P < or = 0.05) whole blood Se concentrations than cows fed sodium selenite, but GSH-Px did not differ (P > or = 0.60) between the two sources. At birth and on May 24 (near peak lactation), calves from cows supplemented with Se had greater (P < or = 0.06) whole blood Se concentrations than calves from cows fed no Se. At birth, calves from cows fed seleno-yeast had greater (P < or = 0.05) whole blood Se concentrations and GSH-Px activities than calves from cows fed sodium selenite. Although no differences were noted in cow and calf performance, significant increases were noted in whole blood Se concentrations and GSH-Px activities in calves at birth as a result of feeding of seleno-yeast compared to no Se or sodium selenite.     

Mineral concentrations of plasma and liver after injection with a trace mineral complex differ among Angus and Simmental cattle

To examine the effects of cattle breed on the clearance rate of an injectable mineral product, 10 Angus and 10 Simmental steers were blocked by breed and initial BW (332 ± 33 kg) and injected with either Multimin 90 (MM) or sterilized saline (CON) at a dose of 1 mL/45 kg BW. Multimin 90 contains 15 mg Cu/mL (as Cu disodium EDTA), 60 mg Zn/mL (as Zn disodium EDTA), 10 mg Mn/mL (as Mn disodium EDTA), and 5 mg Se/mL (as sodium selenite). Steers received a corn-silage-based diet, and inorganic sources of Cu, Zn, Mn, and Se were supplemented at NRC recommended amounts. Jugular blood was collected immediately before injection and at 8 and 10 h post-injection and on days 1, 8, and 15 post-injection. Liver biopsies were collected 3 d before injection and on days 1, 8, and 15 post-injection. Liver and plasma mineral concentration and glutathione peroxidase (GSH-Px) activity data were analyzed as repeated measures. Plasma concentrations of Zn, Mn, and Se were greater (P = 0.01) and Cu tended to be greater (P = 0.12) post-injection in MM steers compared with the CON steers. Regardless of treatment, Simmental cattle had lower plasma concentrations of Cu, Zn, and Se (P ≤ 0.05) when compared with Angus cattle. Erythrocyte GSH-Px activity was greater (P = 0.01) in MM steers compared with CON steers. Liver concentrations of Cu, Zn, and Se were greater (P = 0.05) in MM steers compared with CON steers post-injection. Liver Mn concentrations tended to be greater (P = 0.06) in MM steers compared with CON steers in the days post-injection. Interestingly, Simmental cattle exhibited greater (P = 0.01) liver Mn concentrations in the days after injection compared with Angus cattle (7.0 and 6.0 mg Mn/kg for Simmental and Angus cattle, respectively), regardless of treatment. It is unclear if this breed difference is biologically relevant; however, these data may suggest that differences in liver excretion of Mn exist between the two breeds. Overall, use of an injectable trace mineral increased liver concentrations of Cu and Se through the 15-d sampling period, suggesting that this injectable mineral is an adequate way to improve Cu and Se status of cattle through at least 15 d.     

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.     

Negative effects of energy supplementation at peak lactation of sheep can be offset by the addition of Lactobacillus-fermented plant extracts

Energy supplementation may reduce oxidative stress by correcting a negative energy balance, but in some contexts, it has been shown to increase oxidative stress, especially at peak lactation. The current experiment examined if a pelleted energy supplement with or without the addition of Lactobacillus-fermented seaweed or seaweed plus terrestrial plants extracts affected oxidative stress of ewes from late gestation through to weaning and ewe and lamb production from lambing to weaning. Treatments were either no supplement (CON−), a pelleted supplement only (CON+, 100 g/ewe per d), CON+ with seaweed extract only (SWO, 10 mL/ewe per day), or CON+ with seaweed plus an arrangement of terrestrial plant extract (SWP, 10 mL/ewe per d). Ewes (n = 160; mean initial BW = 72.3 ± 9.5 kg [mean ± SD]) were randomized to pastures (n = 4 pastures per treatment with 10 ewes each). After lambing, ewes with twins were reallocated to pastures (n = 3 pastures per treatment with 10 ewes each) according to lambing date. At 4 wk in milk, supplementation tended to reduce total antioxidant status (TAS; P = 0.10) and increased glutathione peroxidase (GPx) activity compared with nonsupplemented ewes (P = 0.04). The addition of seaweed and terrestrial plants extracts to the concentrate, that is, SWO and SWP, increased TAS and reduced GPx activity compared with CON+ (P < 0.01). Supplementation increased milk yield at weeks 4, 6, and 8 of lactation, and protein, lactose, and total milk solids yield at peak lactation (week 4; P < 0.05). The CON− ewes had greater somatic cell count than the supplemented ewes at weeks 4, 8, and 10 of lactation (P = 0.03). Our results suggest that energy supplementation, alone, increases oxidative stress of lactating ewes, which may relate to increased oxidative phosphorylation. Most importantly, these results indicate that in situations where energy supplementation is needed to increase animal performance, negative effects of energy supplementation around peak lactation can be offset by the addition of Lactobacillus-fermented plant extracts (SWO and SWP) to improve antioxidant status.