Late Gestation Research Articles

Women exposed to famine in early gestation have increased mortality up to age 76 years.

We have previously shown that exposure to famine in early gestation was associated with poorer adult health and, in women, with reduced survival up to age 64. Here, we explore the association between prenatal famine exposure and mortality up to age 76 for men and women separately. We studied adult mortality (>18 years) in men (n = 989) and women (n = 1002) born as term singletons around the time of the 1944-1945 Dutch famine. We compared overall and cause-specific mortality among men and women exposed to famine in late, mid, or early gestation to that among unexposed persons (born before or conceived after the famine) using Cox regression. In total, 500 persons (25.1%) had died after age 18. Women exposed to famine in early gestation had higher overall (HR 1.49, 95% CI 1.00, 2.23), cancer (HR 2.17, 95% CI 1.32,3.58) and cardiovascular mortality (HR 2.33, 95% CI 0.91, 5.95) compared to unexposed women. Mortality rates among men were not different between exposure groups. This study showed that women, but not men, exposed to famine in early gestation had increased overall, cardiovascular and cancer mortality up to age 76. Although prenatal famine exposure affects adult health of both men and women, it seems to only lead to increased mortality among women.

Mineralization of equine proximal sesamoid bones precedes articular cartilage and fibrocartilaginous enthesis maturation in early postgestational development.

To describe the development and maturation of equine proximal sesamoid bones (PSBs) in fetuses and young horses using radiography, microcomputed (micro)-CT, and histology. A descriptive study. Forelimb PSBs from 12 equids ranging in age from 105 days of gestation to 540 days postgestation were evaluated. Radiography was used for preliminary assessment of metacarpophalangeal joint and PSB mineralization, and micro-CT imaging was performed to assess mineralized PSBs. Tissue volume, bone volume fraction, height, width, depth, trabecular thickness, and anisotropy were quantified from midplanar micro-CT sections in 3 dimensions. Midsagittal PSB histologic sections stained with H&E and Safranin O/Fast Green were used to determine the ratio of ossification center to cartilage template size and to describe the formation and development of the cartilage template, ossification center, spherical growth plate, articular cartilage, and entheses. Mineralization of equine PSBs is associated with cartilage canals and a spherical growth plate that undergoes endochondral ossification during the late gestation to early postgestational period. The apical, flexor, basilar, and articular ossification fronts demonstrate morphologic variability. Structural organization of the articular cartilage and entheses occurs concurrently with the development of an underlying plate of compact bone. At 540 days postgestation, the fibrocartilaginous entheses of the flexor cortex of the PSB had yet to mature. Equine PSBs mineralize predominantly by endochondral ossification during the late gestation to early postgestational period. Mineralization precedes maturation of the articular cartilage and fibrocartilaginous entheses. The postgestational maturation of the PSB and its surrounding tissues may predispose young horses to developing lesions at these sites, such as apical avulsion fractures, warranting further investigation.

Androgen-mediated maternal effects and trade-offs: postnatal hormone development, growth, and survivorship in wild meerkats.

Mammalian reproductive and somatic development is regulated by steroid hormones, growth hormone (GH), and insulin-like growth factor-1 (IGF-1). Based largely on information from humans, model organisms, and domesticated animals, testosterone (T) and the GH/IGF-1 system activate sexually differentiated development, promoting male-biased growth, often at a cost to health and survivorship. To test if augmented prenatal androgen exposure in females produces similar developmental patterns and trade-offs, we examine maternal effects in wild meerkats (Suricata suricatta), a non-model species in which adult females naturally, albeit differentially by status, express exceptionally high androgen concentrations, particularly during pregnancy. In this cooperative breeder, the early growth of daughters predicts future breeding status and reproductive success. We examine effects of normative and experimentally induced variation in maternal androgens on the ontogenetic patterns in offspring reproductive hormones (androstenedione, A4; T; estradiol, E2), IGF-1, growth from pup emergence at 1 month to puberty at 1 year, and survivorship. Specifically, we compare the male and female offspring of dominant control (DC or high-T), subordinate control (SC or lower-T), and dominant treated (DT or blocked-T) dams, the latter having experienced antiandrogen treatment in late gestation. Meerkat offspring showed sex differences in absolute T and IGF-1 concentrations, developmental rates of A4 and E2 expression, and survivorship - effects that were sometimes socially or environmentally modulated. Atypical for mammals were the early male bias in T that disappeared by puberty, the absence of sex differences in A4 and E2, and the female bias in IGF-1. Food availability was linked to steroid concentrations in females and to IGF-1, potentially growth, and survival in both sexes. Maternal treatment significantly affected rates of T, E2, and IGF-1 expression, and weight, with marginal effects on survivorship; offspring of DT dams showed peak IGF-1 concentrations and the best survivorship. Maternal effects thus impact offspring development in meerkats, with associated trade-offs: Whereas prenatal androgens modify postnatal reproductive and somatic physiology, benefits associated with enhanced competitiveness in DC lineages may have initial costs of reduced IGF-1, delay in weight gain, and decreased survivorship. These novel data further confirm the different evolutionary and mechanistic pathways to cooperative breeding and call for greater consideration of natural endocrine variation in both sexes.

Cadmium-induced fetal erythropoiesis disturbances in mice

Maternal anemia has been identified as a contributing factor to adverse reproductive outcomes associated with cadmium (Cd) exposure, a common heavy metal. Our recent findings suggest that inhibited erythroid differentiation and enucleation also play significant roles in the direct embryonic toxicity resulting from maternal Cd exposure. However, the effects of Cd exposure on lipid metabolism remodeling, which is essential for physiological erythropoiesis, remain poorly understood. In the present study, pregnant mice were administered low doses of CdCl2 via oral exposure from early to late gestation to mitigate Cd-induced maternal anemia. Compared to vehicle-treated controls, embryos from Cd-treated mice exhibited a slight decrease in weight, though without signs of atrophy. Consistent with our previous observations, fetal livers from Cd-exposed embryos demonstrated a dose-dependent inhibition of erythroid differentiation, as confirmed by ex vivo analysis. Notably, an intrinsic decrease in lipid peroxidation during erythroid differentiation was observed in the bone marrow and fetal livers of vehicle-treated mice, attributed to diminished lipid content. In contrast, this decrease in lipid peroxidation was absent in fetal liver erythroblasts from Cd-treated mice, where an increase in lipid peroxidation was instead noted. These findings elucidate a potential mechanism, lipid peroxidation, underlying Cd-induced embryonic toxicity.

Influence of Maternal Dietary Protein during Late Gestation on Performance of Black Bengal Does and Their Kids.

The present study aimed to elucidate the effect of different levels of dietary protein during late pregnancy on the performance of Black Bengal does and their kids. Twelve does were divided into three groups, with four in each, and three diets, i.e., high protein (18% CP), medium protein (14% CP), and low protein (10% CP) were supplied for 50 days, commencing from 100 days post-coitum to parturition. During the first 100 days of pregnancy, uniform rations with similar ingredients were provided to fulfill the nutrient requirements depending on the live weight of does. All three diets were isocaloric (10.0 MJ/kg DM). Data were subjected to one-way ANOVA, and the significance of the difference among means was determined by Duncan's Multiple Range Test (DMRT). The main effects of diet and sex, as well as their interaction, were analyzed by two-way ANOVA by using the GLM procedure. The relative expression values of qPCR were calculated by using the 2-ΔΔCt analysis method. Live weight gain was significantly (p < 0.05) higher in high-protein-fed dams than other groups during the experimental period. The milk yield of does was significantly (p < 0.05) higher in high-protein-fed goats than in the low-protein group. The lactation length of does was significantly (p < 0.05) higher in the high- and medium-protein-fed does than in the low-protein-fed does. The duration of post-partum anestrus of does was significantly (p < 0.05) higher in the low-protein-fed dams than in the high-protein group. The birth weight of kids tended to be higher in the high-protein group but did not differ significantly among the treatment groups. In male kids, weaning weight, final weight, live weight gain, and average daily gain were significantly (p < 0.05) higher than in female kids. Weaning weight was higher (p < 0.05) in kids of the high-protein-fed does than the low-protein group. Final weight and live weight gain were significantly (p < 0.05) higher in kids of the high-protein-fed does than in the low-protein-fed group. On the other hand, average daily gain was significantly (p < 0.05) higher in kids of the high- and medium-protein-fed does than the low-protein group. The average body length and wither height of kids at the 32nd week was significantly (p < 0.05) higher in kids of high-protein-fed does than those of the low-protein-fed group. The average heart girth of kids at the 32nd week was significantly (p < 0.05) higher in kids of high-protein-fed does than the medium- and low-protein groups. The survival rate of kids was higher in the medium- and high-protein-fed does than in low-protein group. Hot carcass weight and ether extract content of meat were significantly (p < 0.05) higher in the high-protein group than in the other groups. The dressing percentage was significantly (p < 0.05) higher in the kids of high-protein-fed does than low-protein-fed goats. The expression of the H-FABP gene was significantly (p < 0.05) higher in kids of high-protein-fed does than those of the medium- and low-protein groups. In conclusion, maternal dietary protein levels positively influences the production performance of Black Bengal does and their kids.

Effects of Interactions between Feeding Patterns and the Gut Microbiota on Pig Reproductive Performance.

The feeding mode is an important factor affecting the reproductive performance of pigs. The composition and expression of the intestinal microbiota are closely related to the physiological and biochemical indicators of animals. Therefore, to explore the impact of different feeding patterns on the reproductive performance of pigs, this study collected reproductive performance data from 1607 Yorkshire pigs raised under different feeding patterns and conducted a fixed-effect variance analysis. Among them, 731 were in the artificial feeding (AM) group and 876 were in the feeding station feeding (SM) group. Additionally, 40 Yorkshire sows in the late gestation period were randomly selected from each feeding mode for intestinal microbiota analysis. The results of the analysis showed that, in the AM group, both the number of birth deformities (NBD) and the number of stillbirths (NSB) were significantly greater than they were in the SM group (p < 0.05). Additionally, the total number born (TNB) in the AM group was significantly lower than that in the SM group (p < 0.05). The results of the intestinal microbiota analysis revealed that at the phylum level, there were significant differences in nine bacterial taxa between the AM and SM groups (p < 0.05). At the genus level, the abundance of a variety of beneficial bacteria related to reproductive performance in the SM group was significantly greater than that in the AM group. Finally, fecal metabolomic analysis revealed that the contents of butyric acid, isovaleric acid, valeric acid, and isobutyric acid, which are associated with reproductive performance, in the feces of sows in the SM group were significantly higher than those in the AM group (p < 0.05). These results indicate that different feeding methods can affect the gut microbiota composition of Yorkshire pigs and further influence the reproductive performance of pigs through the gut microbiota-metabolic product pathway. The results of this study provide valuable insights for further exploring the relationships between feeding modes, intestinal microbial composition, and host phenotypes.

PSLBII-4 The effect of standardized ileal digestible sulfur amino acid intake during late gestation on gilt whole-body nitrogen retention and subsequent litter performance

Abstract Gestating gilts [n = 27; body weight (BW) = 158 ± 5.5 kg] were used to determine the effect of standardized ileal digestible (SID) sulfur amino acid (SAA) intake during late gestation on whole-body nitrogen (N) retention and subsequent litter performance. Gilts were assigned to one of two experimental diets that provided SAA at 60 or 200 % of estimated requirements during late gestation (0.29 and 0.92 % SID SAA, respectively; n = 15 and 12, respectively; Table 1 and 2). Each gilt received 2.53 kg of the assigned diet between gestation d 90 and farrowing; standard lactation and nursery diets were provided to gilts after farrowing and offspring after weaning, respectively. Gilt whole-body N balance was determined between d 107 and 109 of gestation using total urine collection and fecal grab-sampling. After farrowing, litters were standardized to 13 piglets and were not offered creep feed. Whole-body N retention was greater in gilts fed the diet containing 0.92 vs. 0.29 % SID SAA in late gestation (27.2 vs. 19.3 ± 1.8 g/d; P &amp;lt; 0.05; Table 3), but the number of piglets born alive, litter birth weight, subsequent piglet growth rates, and litter size at weaning were not different between treatment groups. The post-weaning growth performance of offspring was also not influenced by maternal dietary treatment in late gestation (Table 4). At farrowing, the post-absorptive plasma concentration of Cys tended to be less (P = 0.072) and taurine was greater (P &amp;lt; 0.01) for gilts fed 0.92 vs. 0.29 % SID SAA in late gestation; however, there were no differences in plasma SAA metabolites concentrations for gilts at weaning or offspring at birth (Table 5. At weaning, offspring from gilts fed 0.92 % SID SAA had greater plasma homocysteine (P &amp;lt; 0.05) and plasma Cys concentrations (tendency; P = 0.072) vs. offspring from gilts fed 0.29 % SID SAA in late gestation. Three weeks after weaning, plasma taurine concentration was less (P &amp;lt; 0.05) for offspring from gilts fed 0.92 vs. 0.29 % SID SAA in late gestation (Table 6). Six weeks after weaning, plasma glutathione concentration tended to be less (P = 0.057) for offspring from gilts fed 0.92 vs 0.29 % SID SAA in late gestation. When SAA were fed below estimated requirements during late gestation, whole-body N retention was reduced, but fetal growth appeared to be maintained, likely at the expense of maternal N retention. Such divergences in dietary SAA supply in late gestation had no effect on subsequent offspring growth performance, but it appeared that offspring SAA metabolism was impacted until at least 6 wk after weaning. The influence of differences in sulfur AA metabolites on offspring performance beyond the nursery phase remains unknown. Therefore, carry-over effects of maternal SAA supply in late gestation should be considered when developing feeding recommendations for gestating gilts.

PSIV-6 Blood biomarkers of oxidative stress in offspring from dams infected with bovine viral diarrhea virus during late-term gestation

Abstract The objective of this experiment was to examine the impact of dams infected with bovine viral diarrhea virus (BVDV) during late gestation on inflammatory blood biomarkers in their offspring. Fetal infection with BVDV before d 125 to 150 of gestation results in the birth of immunotolerant, persistently infected (PI) calves. Infection of BVDV during late gestation results in transient fetal infections (TI). It was hypothesized that offspring of dams transiently infected with BVDV on d 175 of gestation would have greater inflammatory blood biomarkers than control offspring. Unvaccinated, yearling Hereford heifers (n = 24), seronegative for antibodies to BVDV1 and BVDV2 were bred by artificial insemination with X chromosome-bearing sperm from an Angus sire. On d 175 of pregnancy, heifers were intranasally inoculated with either Dulbecco’s Modified Eagle Medium + 2% horse serum (sham control) or 4.0 log TCID50 noncytopathic type 2 BVDV to generate control and transient infected calves, respectively. All BVDV-inoculated dams seroconverted by d 14 post-inoculation and all sham-inoculated control dams remained seronegative. Twelve, seronegative control heifer calves were born to the control dams, and 11 seropositive (to type 2 BVDV) TI heifer calves were born to BVDV-inoculated dams. All offspring were raised on pasture until weaning. At weaning, all calves were transported to our feedlot research facility, housed in one group feedlot pen, and transitioned to a high-energy concentrate-based diet until reaching an approximate body weight (BW) of 600 kg. Upon arrival, all animals received a standard heifer growth implant containing 200 mg of testosterone propionate and 20 mg of estradiol benzoate, a modified live viral vaccine containing IBR-BRSV-PI3, and were dewormed. Jugular blood samples were obtained every 28 d until harvest (280 d on feed) and analyzed for biomarkers of inflammation. Data were analyzed as a randomized block design with the MIXED procedures of SAS. There was a treatment x time interaction (P &amp;lt; 0.05) for plasma ceruloplasmin and the oxidized form of glutathione. On d 0 and 28 of the feeding period, all biomarkers were similar across treatments. By d 56 of the feeding period, ceruloplasmin (P &amp;lt; 0.03) and the oxidized form of glutathione (P &amp;lt; 0.01), indicators of chronic inflammation, were increased in plasma samples from TI heifers compared with controls. These parameters remained greater in TI heifers compared with controls throughout the feeding period. There were no treatment or treatment x time interactions for plasma interferon (INF)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-6, and haptoglobin. These data suggest that TI heifers may be experiencing a greater level of oxidative stress later in the finishing period. This research was supported by USDA-NIFA Grant #2019-67015-29866.

PSXI-2 Impact of flexible prepartum supplementation strategies on cow-calf and subsequent progeny feedlot performance

Abstract Implementation of minimal supplemental protein strategies during late gestation may have the potential to minimize any negative postweaning progeny performance while decreasing feed costs. A 3-yr study was conducted to evaluate the effects of mid- to late-gestation supplementation strategies on reproduction, cow body weight (BW), and calf performance in May-calving mature cows grazing upland native range. Cows received one of 3 supplementation strategies: 1) 0.227 kg/d of a 30% CP distillers-based supplement (HalfSupp), 2) 0.454 kg/d of a 30% CP distillers-based supplement (Supp), or 3) brief and intermittent supplementation of Supp at 0.454 kg/cow based on periods of acute environmental stress, such as snow cover, wet winter events, and is best described as flexible supplementation (Flex). Supplementation was initiated in December each year and terminated approximately 30-d prior to the start of the calving season in April. Across all 3 yr, average supplement feeding rate was 25.5, 50.9, and 5.4 kg/cow during the 112-d supplemental period, which resulted in average yearly prepartum supplemental costs of $27.30, 54.60, and 1.99 for HalfSupp, Supp, and Flex; respectively. After weaning, steers grazed sub-irrigated meadow with a dried distiller grain supplement until May. In May, all steers grazed sub-irrigated meadow without additional supplement until August/September when steers were shipped to West Central Research and Extension Center (WCREC). Steers were placed in a GrowSafe feeding system for the rest of the finishing feeding period. Each year, steers were slaughtered at a commercial facility (Tyson Fresh Meats, Lexington, NE) when estimated visually to have 1.3 cm fat thickness over the 12th rib as a group. Cow BW was not different (P = 0.86) at the initiation of supplementation in Jan. However, cows fed Half had a lighter (P &amp;lt; 0.01) BW at pre-calving and tended (P = 0.08) to have a lighter BW at pre-breeding than their counterparts. After a 45-d breeding season, pregnancy rates were not influenced (P = 0.91) by prepartum supplementation strategies. Prepartum supplementation strategies did not influence (P &amp;gt; 0.56) preweaning calf BW at birth, pre-breeding, and weaning. In addition, steer backgrounding BW was also not influenced (P &amp;gt; 0.63) by prepartum supplementation strategy of their dam. Upon entry into the feedlot, steer BW was not impacted (P &amp;gt; 0.84) by prepartum supplementation strategy of their dam. Feedlot performance (BW, average daily gain, and feed efficiency) was not influenced (P &amp;gt; 0.59) by prepartum supplementation strategy of their dam. After harvest, all carcass characteristics were not impacted (P &amp;gt; 0.11) by the prepartum supplementation strategy of the dam. Considering the cost for prepartum supplementation, feeding a protein supplement just during environmentally stressful periods during gestation appears to be a viable alternative to more conventional methods and reduces winter feed costs.

A Novel Non-Invasive Murine Model of Neonatal Hypoxic-Ischemic Encephalopathy Demonstrates Developmental Delay and Motor Deficits with Activation of Inflammatory Pathways in Monocytes.

Neonatal hypoxic-ischemic encephalopathy (HIE) occurs in 1.5 per 1000 live births, leaving affected children with long-term motor and cognitive deficits. Few animal models of HIE incorporate maternal immune activation (MIA) despite the significant risk MIA poses to HIE incidence and diagnosis. Our non-invasive model of HIE pairs late gestation MIA with postnatal hypoxia. HIE pups exhibited a trend toward smaller overall brain size and delays in the ontogeny of several developmental milestones. In adulthood, HIE animals had reduced strength and gait deficits, but no difference in speed. Surprisingly, HIE animals performed better on the rotarod, an assessment of motor coordination. There was significant upregulation of inflammatory genes in microglia 24 h after hypoxia. Single-cell RNA sequencing (scRNAseq) revealed two microglia subclusters of interest following HIE. Pseudobulk analysis revealed increased microglia motility gene expression and upregulation of epigenetic machinery and neurodevelopmental genes in macrophages following HIE. No sex differences were found in any measures. These results support a two-hit noninvasive model pairing MIA and hypoxia as a model for HIE in humans. This model results in a milder phenotype compared to established HIE models; however, HIE is a clinically heterogeneous injury resulting in a variety of outcomes in humans. The pathways identified in our model of HIE may reveal novel targets for therapy for neonates with HIE.

PSI-21 Limited impact of hypothyroidism on porcine fetal growth during mid to late gestation

Abstract In the fetal pig, both circulating thyroid hormone and growth rate are known to increase throughout gestation; however, the functional association between these coincident factors has not been established. Thus, the objective of this project was to investigate this cause-and-effect relationship by evaluating the impact of induced fetal hypothyroidism on fetal growth during mid to late gestation. To induce fetal hypothyroidism, n = 12 pregnant gilts were orally treated with the goitrogen methimazole (MMI) at a dose of 5 mg/kg/d for 21 d, with n = 3 gilts starting treatment on gestation d 34, 45, 55 and 65. An equivalent group n = 12 of gilts were sham treated for the same periods to produce gestationally age-matched euthyroid control litters (CON). Upon completion of the treatment period, gilts were humanely euthanized, and the resulting populations of n = 174 MMI and n = 166 CON fetuses deeply phenotyped. No meconium-stained fetuses were observed at any time point, and only 5 mummified fetuses were observed (3 CON, 2 MMI), indicating treatment has no effect on fetal viability. Fetal body weight (BW) and the weights of individual organs including thyroid, liver, heart, lung, kidney, spleen, and brain were collected. In addition, fetuses were imaged in both left and right lateral recumbency for subsequent morphometric assessment using a custom analysis pipeline in ImageJ. Image analysis yielded parameters including crown-rump length, girth, brow length, depth at the snout/skull junction, depth at the snout/nose junction, and area under the skull curvature (AUC). Left and right measurements for all morphometric parameters were found to be highly correlated (r2 &amp;gt; 0.9) indicating a repeatable measure using this approach. Statistical analysis of all phenotypic differences was carried out using a linear mixed effect model including gestational age and treatment as fixed effects and gilt as a random effect. A significant increase in both absolute and relative thyroid weights indicated the development of goiter and thus, successful induction of hypothyroidism within the MMI litters. In addition, a significant treatment by time interaction was observed, with 0.014 g and 0.21 g increase at d 55 and 66, respectively, indicating reduced compensatory action within the fetal hypothalamic-pituitary-thyroid axis during this earliest period. Liver weight as a percentage of BW decreased from 6.06% to 2.56% between d 55 and 86 in the CON group but was significantly increased at all time points in response to MMI induced hypothyroidism (P &amp;lt; 0.01). A corresponding increase in brain to liver weight ratio over time was suppressed in MMI fetuses (P &amp;lt; 0.05). While all other phenotypic parameters were significantly altered by gestational age, there was no significant impact of fetal hypothyroidism. Collectively, the results indicate that fetal growth during mid to late gestation is not driven by fetal thyroid hormone.

PSIV-15 Effect of transient fetal bovine viral diarrhea virus infection on postnatal growth, estimated dry matter digestibility, glucose concentrations, and carcass characteristics

Abstract Fetal infection of bovine viral diarrhea virus (BVDV) before d 125 to 150 of gestation results in the birth of immunotolerant, persistently infected (PI) calves. Infection of BVDV during late gestation results in transient fetal infections (TI). Unvaccinated, yearling Hereford heifers (n = 25), seronegative for antibodies to BVDV1 and BVDV2, were bred by artificial insemination with X chromosome-bearing sperm from an Angus sire to examine the impact of TI on postnatal growth, estimated dry matter digestibility, blood glucose concentrations, and carcass characteristics. On d 175 of pregnancy, heifers were intranasally inoculated with either DMEM + 2% horse serum (sham control) to generate control calves or 4.0 log TCID50 noncytopathic type2 BVDV to generate TI calves. All sham-inoculated control dams remained seronegative, and all BVDV-inoculated dams seroconverted by d 14 post-inoculation. Sham-inoculated control dams (n = 12) and BVDV-inoculated dams (n = 12) gave birth to live calves. All control offspring were seronegative, and all TI offspring were seropositive for antibodies to type 2 BVDV at birth. All offspring were raised on pasture until weaning. At weaning, all calves were transported to our feedlot research facility, housed in one group feedlot pen, and transitioned to a high-energy concentrate-based diet until reaching an approximate BW of 600 kg. Upon arrival at the feedlot, all animals received a standard heifer growth implant, a modified live viral vaccine containing IBR-BRSV-PI3 and were dewormed. Heifer BW and jugular blood samples were collected every 28 d. On d 84 of the feeding period, titanium dioxide was added to the diet of 12, age-paired, individually fed, heifers (3 control and 3 TI heifers; approximately 1 yr of age) for 28 d and used to estimate dry matter digestibility. After approximately 280 d on feed heifers were transported to a USDA-inspected abattoir and harvested. The TI heifers had lighter birth weights (P &amp;lt; 0.03) and final BW (P &amp;lt; 0.04) when compared with control heifers. Average daily gain was greater (P &amp;lt; 0.01) in control compared with TI heifers. Blood glucose concentrations were similar between control and TI heifers at all sampling time points. Dry matter intake of individually fed heifers was similar across treatments. TI heifers had a 2.2% lesser (P &amp;lt; 0.05) dry matter digestibility and lighter (P &amp;lt; 0.01) hot carcass weights compared with controls. These data suggest that TI fetal BVDV infection negatively impacts growth throughout the feeding period, possibly by impacting gastrointestinal tract function. This research was supported by USDA-NIFA Grant # 2019-67015-29866.

281 Changes in satellite cell number in maternal and fetal muscle with 5-hydroxy tryptophan supplementation during late gestation

Abstract Toxic tall fescue contains ergot alkaloids, which induce vasoconstriction in livestock, leading to fescue toxicosis. This condition can impact muscle development due to altered blood flow. Supplementation with 5-HTP may counteract the vasoconstrictive effects of fescue alkaloids. We aimed to investigate the influence of 5-HTP supplementation on satellite cells, myoblast, and preadipocyte numbers in maternal and fetal muscle during late gestation in Suffolk ewes. We hypothesized that 5-HTP supplementation would mitigate the effects of fescue toxicosis on muscle cell populations, potentially promoting muscle development and regeneration in maternal and fetal tissues. Suffolk ewes (n = 75), naïve to toxic tall fescue, were blocked by body condition score and body weight into 10 groups for synchronization. Ewes were confirmed pregnant using transabdominal ultrasound, and lamb number was estimated at gestational day (gd) 60. Pregnant ewes carrying twins (n = 30) were randomly assigned to one of three treatments: 1) negative control (CON, n = 10), 2) toxic tall fescue seed containing 1.77 mg ewe-1ּ d-1 ergovaline/ergovalinine plus 5-HTP (2.5 mg/kg BW) supplement (5HTP, n = 10), or 3) positive control, fed toxic tall fescue seed containing 1.77 mg ewe-1ּ d-1 ergovaline/ergovalinine (E+, n = 10). Ewes were individually fed a total mixed ration from gd 78 to gd 85 of pregnancy and then TMR plus treatment (CON, E+ or 5HTP) from gd 86 to d 111. On gd 112, terminal necropsies were performed, and semimembranosus muscle (SM) from the ewe and fetus was removed. Weights were obtained, and then samples were digested using pronase (1.5mg/mL) to isolate preadipocyte (PP1), myoblasts (PP2) and satellite cell (PP3) fractions using a pre-plating technique. Cells were quantified using a Neubauer-hemocytometer and trypan blue to also assess cell viability and changes in cell number. Fetal SM had a greater (P &amp;lt; 0.05) number of pre-adipocytes, myoblasts, and satellite cells per gram of tissue digested in comparison with the ewes. Pre-adipocyte and myoblast number per gram of tissue digested did not differ (P &amp;gt; 0.05) by treatment. The 5HTP group had the greater (P &amp;lt; 0.05) number of satellite cells per gram of tissue digested in comparison with the CON group. Satellite cell numbers tended (P &amp;lt; 0.10) to be greater in the 5HTP group in comparison to the E+ group. Satellite cell numbers from CON and E+ treatment groups did not differ (P &amp;gt; 0.05). In conclusion, 5-HTP supplementation during late gestation in Suffolk ewes exposed to toxic tall fescue significantly increased satellite cell numbers in maternal and fetal muscle tissues. This suggests a potential mitigation of the impact of fescue toxicosis on muscle cell populations.

387 Impacts of rumen protected omega-6 fatty acid supplementation on cow reproduction and calf growth

Abstract Maternal nutrition during pregnancy is crucial for proper fetal development. Rumen protected omega-6 (ω-6) fatty acids (FA) may improve health and reproductive success in beef cattle. Previous research studied the effects of supplementing ω-6 on cow production either during late gestation or post-breeding but not during both stages. Our objective was to determine the effects of ω-6 supplementation during late gestation and post-breeding on cow reproduction and calf pre-weaning growth. Eighty cows were assigned to either a saturated FA control (C) or rumen protected ω-6 supplements for 40 d before parturition (PRE) and/or 35 d after artificial insemination (AI, POST) using a 2 × 2 factorial: PRE C-POST C(n = 19); PRE C-POST ω-6(n = 19); PRE ω-6-POST ω-6(n = 17); PRE ω-6-POST C(n = 18). Cows were fed ad libitum hay and water when on/off supplementation periods. Supplements were provided in low moisture tubs. Individual animal intake of supplement was measured by a GrowSafe system. Cow body weights and plasma FA concentrations were measured prior to and after supplementation during each period. Calves were weighed at birth, branding, 150 d old and weaning. Reproductive measurements included postpartum estrus activity, estrus response at fixed-time AI (FTAI), and pregnancy rates. Blood plasma for progesterone analysis was collected on d 7 post-AI on all cows. Corpus luteum (CL) area was measured on d 7 via transrectal ultrasonography on a subset of cows during the POST period (PRE ω-6-POST ω-6 n = 8; PRE C-POST C n = 8; PRE C-POST ω-6 n = 8; PRE ω-6-POST C n = 8). The relationship between supplement intake and plasma FA concentration was analyzed via linear regression, and all other variables were analyzed via ANOVA. Supplement intakes within treatments and between the PRE and POST supplemental periods were highly variable. Body weights remained similar for cows (P = 0.52), but POST ω-6 calves had larger weaning weights than POST C calves (P = 0.02). There was a positive linear relationship (r2 = 0.14, P &amp;lt; 0.03) between supplement intake and plasma FA for PRE ω-6 and POST ω-6. Positive linear relationships between intake and plasma ω-6 FA concentration were observed for PRE C (r2 = 0.11, P &amp;lt; 0.05), PRE ω-6 (r2 = 0.2, P &amp;lt; 0.007) and POST ω-6 (r2 = 0.31, P = 0.0005). Post-partum estrus activity was similar (P = 0.81) between PRE C and PRE ω-6 cows, and estrus response at FTAI was similar (P = 0.13) between POST C and POST ω-6 cows. POST ω-6 cows had larger CL areas than POST C cows (P = 0.03); however, blood progesterone concentrations at d 7 did not differ between treatments (P = 0.65). There was no difference in conception to FTAI between POST C and POST ω-6 (P = 0.08). These results indicate that free choice ω-6 FA supplementation during late gestation and post-AI result in large variation in intake between cows that influence plasma concentrations, but did not markedly alter reproductive measures in mature beef cows.

140 Effects of ɷ-3 PUFA supplementation during late gestation to first-calf beef heifers on physiological and performance responses of offspring

Abstract The objectives of this experiment were to evaluate the effects of ɷ-3 PUFA supplementation to late gestation first-calf beef heifers on milk and immunoglobulin production and performance and physiological responses of the offspring. Non-lactating, pregnant Angus heifers (n = 44) were ranked by age, body weight (BW), and body condition score (BCS) and allocated to receive DDG + 1 of the 2 treatments: 1) 234 g/heifer per feeding of Ca salts of PUFA based on eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids (OMG, Strata; Virtus Nutrition LLC, Corcoran, CA; n = 22), 2) 234 g/heifer per feeding of Ca salts of saturated and monosaturated fatty acids based on palmitic and oleic acids (CON; EnerGII, Virtus Nutrition, LLC; n = 22; Table 1). The animals were gathered each week on Mondays, Wednesdays, and Fridays and individually fed DDG + treatments. Immediately after calving, heifer-calf pairs were removed from their respective treatments and assigned to the general management of the research herd until weaning, which did not include fatty acid supplementation. Calves were transported to a feedyard for a 90-d preconditioning and feedlot receiving period. Initial cow BW and BCS were similar (P ≥ 0.49) among treatments. No differences were also detected (P ≥ 0.33) for BW or BCS change, and at calving BW or BCS (Table 3). No differences were observed between groups for average colostrum composition (P &amp;gt; 0.37). However, there was an increase in colostrum fat percentage (P = 0.03) and a tendency of greater concentration of colostrum IgG (P = 0.08) in OMG heifers compared with the control group. No significant differences were observed among treatments at calving results (P &amp;gt; 0.83; Table 3). However, a tendency was observed for crown to rump measure (P = 0.07). During the preconditioning period, there was a difference among groups for final BW (P = 0.04) and average daily gain (ADG; P = 0.05), remaining throughout the receiving phase among treatments for initial BW (P = 0.04), final BW (P = 0.04) and ADG (P = 0.05). A tendency (P = 0.09) for greater NEFA concentration and greater cortisol concentrations (P = 0.05) was observed in OMG vs. CON cohorts (Table 4, Table 5). Supplementation during late gestating first-calf beef heifers yielded similar outcomes on cow and offspring performance from birth to weaning; however, OMG calves were 6 kg heavier when compared with CON after being fed a high-energy feedlot diet, meaning that ɷ-3 PUFAs supplemented during late gestation might be an alternative to optimize feedlot responses of the offspring.

Sevoflurane anesthesia during late gestation induces cognitive disorder in rat offspring via the TLR4/BDNF/TrkB/CREB pathway.

Sevoflurane (Sevo) is widely used for general anesthesia during pregnancy. Emerging evidence indicates that maternal Sevo exposure can trigger developmental neurotoxicity in the offspring. Nonetheless, the underlying mechanisms need further investigation. Pregnant Sprague-Dawley rats on gestational day 18 were exposed to 3.5% Sevo to induce the rat model of neurotoxicity. TAK-242, a TLR4 inhibitor, was administrated to inhibit the signaling transduction. Hippocampal tissues of rat offspring were harvested for immunohistochemical staining, TUNEL staining, Western blotting, ELISA, and measurement of oxidative stress-related markers. Serum samples were collected to evaluate lipid metabolism-associated factors. Morris water maze was implemented to test the cognitive function of offspring rats. Rat hippocampal neurons were isolated to elucidate the effect of TAK-242 on the BDNF/TrkB/CREB signaling in vitro. The results showed that maternal Sevo exposure during the third trimester induced neuroinflammation, lipid metabolism disturbance, and oxidative stress, and impaired the spatial learning and memory of rat offspring. Sevo upregulated TLR4 and impeded BDNF/TrkB/CREB signaling transduction in the hippocampus of rat offspring; TAK-242 administration reversed these effects. In conclusion, Sevo anesthesia during late gestation impairs the learning and memory ability of rat offspring possibly by promoting neuroinflammation and disturbing lipid metabolism via the TLR4/BDNF/TrkB/CREB pathway.

112 Effects of maternal body condition on colostrum, foal weight, and foal IgG concentration

Abstract Foals are born with little to no immunity and rely on maternal colostrum to develop adequate circulating immunoglobulin G (IgG) concentrations in the periparturient period. Colostrum directly impacts the health of the foal, and there are limited data assessing how maternal metabolism and body condition impacts IgG in colostrum and in the foal postnatally. To determine the influence of maternal body condition score (BCS) and cresty neck score (CNS) on glucose and insulin metabolism in the pregnant mare, colostrum composition, and colostrum and foal IgG concentrations, light breed mares (n = 6) were divided into two groups based on BCS and CNS at 315 ± 0.45 d of gestation. The groups were identified as moderately obese (MO; n = 3, BCS) and lean (LN; n = 3). Mares were fasted overnight and then underwent an intravenous (iv) glucose tolerance test at 315 ± 0.45 d gestation. Blood samples were collected at -30, -15 and 0 min and mares were administered dextrose iv [0.3 g/kg body weight (BW)] over 3.7 ± 0.17 min followed by an intravenous infusion of insulin (0.3 mU/kg BW) 20-min later. Additional blood samples were collected 2, 5, 10, 15, 20, 25, 30, 45, 60, and 120 min after initiation of dextrose infusion. At parturition, a colostrum sample was collected before foals nursed and analyzed for protein and fat, and IgG concentration. A foal blood sample was collected 18 h after birth to determine passive transfer of IgG. Placental, mare, and foal weights were measured at birth. Data were analyzed using a t-test with significance at P ≤ 0.05 and a tendency at 0.05 &amp;lt; P ≤ 0.10. The MO group had greater BCS (P = 0.01) and CNS (P = 0.01) than the LN group. Moderately obese mares tended to have 9% greater glucose area under the curve (AUC) after dextrose (P = 0.10) and a 9% greater glucose AUC after insulin infusion (P = 0.10) than LN mares. Colostrum IgG concentrations, and protein and fat content (P ≥ 0.3) did not differ between groups. Foal serum IgG concentrations, foal BW, and placental weights were similar between groups (P ≥ 0.8). The ratios between foal BW and placenta weight, and between foal BW and mare BW were similar between groups (P ≥ 0.3). Moderately obese maternal BCS and CNS scores may decrease maternal glucose clearance during late gestation but did not impact colostrum quality or foal IgG concentrations within 24 h postpartum. As the equine fetus matures later in gestation than other livestock species and relies heavily on glucose uptake from the placenta, it is critical to increase our understanding of the impacts of maternal obesity and glucose clearance on foal development and pre- and post-natal health.

255 Awardee Talk: Nutritional management to optimize cow-calf production in Southeast

Abstract Nearly one-half of beef cows in the United States are located in southern states where cow-calf operations predominate. Grazing management in cow-calf systems can be affected by environmental and seasonal conditions, often leading to nutrient deficiency, particularly during late gestation of beef females. Maternal nutrition during the last trimester of gestation can influence offspring development and health, and can be explored to optimize maternal and progeny performance. The objective of this presentation is to share nutritional and management strategies for pregnant beef cows and their long-term effects on offspring growth and physiology. Study 1 investigated the effects of timing of maternal protein supplementation during all last trimester of gestation (LATE84), only the first 42 d of last trimester of gestation (LATE42), or no prepartum supplementation (NOSUP) on offspring pre- and post-weaning performance. At weaning, LATE84 calves were the heaviest, followed by LATE42, and NOSUP (P ≤ 0.05). Steer serum parainfluenza-3 titers were greater (P = 0.03) for LATE42 vs. NOSUP and tended to be greater for LATE84 (P = 0.10) vs. NOSUP steers. Marbling and the proportion of steers grading choice were greater (P ≤ 0.04) for LATE42 vs. NOSUP, and intermediate for LATE84. Study 2 evaluated the effects of frequency of maternal protein supplementation on offspring pre-weaning growth. Cows received the same weekly amount of supplement (7 kg·cow⁻¹·wk⁻¹) but with different frequencies: once a week (1X), three times per week (3X), every day (7X), or no prepartum supplementation (NOSUP) during the last 80 d of gestation. At weaning, calves born from 7X cows were the heaviest (P ≤ 0.05), followed by 3X and 1X, which did not differ between them (P = 0.54), and NOSUP calves were the lightest (P ≤ 0.05). Study 3 evaluated the use of monensin supplementation during the last 77 d of gestation and its impacts on offspring performance. Treatments consisted of no prepartum supplementation (NOSUP), supplementation of dried distillers grains at 1 kg·cow⁻¹·d⁻¹ added with 0 (SUP) or 200 mg/d of monensin (SUPMO). At weaning, SUPMO calves were the heaviest (P ≤ 0.05), SUP intermediate, and NOSUP were the lightest. Experiment 4 consisted of pregnant heifers receiving the supplementation of 1 kg/d of soybean hulls dry matter added (BAC) or not (CON) with a Bacillus-based DFM mixture during late gestation (d 0 to 139) and early lactation (d 139 to 242). Post-weaning body weight gain and indicators of humoral immune response post-vaccination were greater for BAC vs. CON calves (P ≤ 0.05). Therefore, changing the time and frequency of supplementation, and the use of additives and probiotics during late gestation of beef females are effective alternatives to improve offspring pre- and post-weaning growth and immune response.

Maternal Supplementation with Dietary Betaine during Late Gestation Increased Ewe Plasma Creatine and Lamb Thermoregulation under Field Conditions.

Twin lamb mortality is a significant economic problem impacting the Australian sheep industry. Maternal betaine supplementation improved lamb vigour and early post-natal survival when ewes and lambs were housed indoors, suggesting that betaine may be beneficial to feed under extensive pasture systems. This study investigated whether maternal betaine supplementation during late gestation would improve Merino twin lamb live weight, thermoregulation, vigour and survival to weaning under field conditions. Ewes received dietary betaine at either 0 g/day (CTL; n = 115) or 4 g/day from day 110 of gestation (dG 110) until ~49 days post-partum (pp) (BET; n = 115). Measures indicative of lamb viability and survival were collected within 4-24 h of birth and at ~49 days pp and ~93 days pp. BET ewes had higher creatine and creatinine concentrations at dG 130 than CTL ewes (p < 0.05). BET lambs had a higher rectal temperature within 4-24 h following birth than CTL lambs (p < 0.05). CTL lambs were heavier at ~49 days pp and grew faster from birth to ~49 days pp than BET lambs (both p < 0.05). The time taken after release from the researcher to first suckling was quicker in the CTL lambs than BET lambs (p < 0.05). This study demonstrated that supplementing betaine increased creatine concentration in twin-bearing ewes and thermoregulatory capacity in neonatal lambs under extensive grazing systems.

Structural and functional fetal cardiac imaging using low field (0.55 T) MRI.

This study aims to investigate the feasibility of using a commercially available clinical 0.55 T MRI scanner for comprehensive structural and functional fetal cardiac imaging. Balanced steady-state free precession (bSSFP) and phase contrast (PC) sequences were optimized by in utero studies consisting of 14 subjects for bSSFP optimization and 9 subjects for PC optimization. The signal-to-noise ratio (SNR) of the optimized sequences were investigated. Flow measurements were performed in three vessels, umbilical vein (UV), descending aorta (DAo), and superior vena cava (SVC) using the PC sequences and retrospective gating. The optimized bSSFP, PC and half-Fourier single shot turbo spin-echo (HASTE) sequences were acquired in a cohort of 21 late gestation-age fetuses (>36 weeks) to demonstrate the feasibility of a fetal cardiac exam at 0.55 T. The HASTE stacks were reconstructed to create an isotropic reconstruction of the fetal thorax, followed by automatic great vessel segmentations. The intra-abdominal UV blood flow measurements acquired with MRI were compared to ultrasound UV free-loop flow measurements. Using the parameters from 1.5 T as a starting point, the bSSFP sequences were optimized at 0.55 T, resulting in a 1.6-fold SNR increase and improved image contrast compared to starting parameters, as well as good visibility of most cardiac structures as rated by two experienced fetal cardiologists. The PC sequence resulted in increased SNR and reduced scan time, subsequent retrospective gating enabled successful blood flow measurements. The reconstructions and automatic great vessel segmentations showed good quality, with 18/21 segmentations requiring no or minor refinements. Blood flow measurements were within the expected range. A comparison of the UV measurements performed with ultrasound and MRI showed agreement between the two sets of measurements, with better correlation observed at lower flows. We demonstrated the feasibility of low-field (0.55 T) MRI for fetal cardiac imaging. The reduced SNR at low field strength can be effectively compensated for by strategically optimizing sequence parameters. Major fetal cardiac structures and vessels were consistently visualized, and flow measurements were successfully obtained. The late gestation study demonstrated the robustness and reproducibility at low field strength. MRI performed at 0.55 T is a viable option for fetal cardiac examination.