Effects of maternal nutrient restriction followed by realimentation during early and mid-gestation in beef cows. II. Placental development, umbilical blood flow, and uterine blood flow responses to diet alterations

Characterization of placentome vascular perfusion in relation to pregnancy associated glycoproteins throughout gestation in pregnant beef heifers

During pregnancy, blood flow to the uterus changes to support fetal demand. Placentomes serve as vascular attachment sites on the placenta for exchange of gases, nutrients, and metabolic products. Non-invasive methods of ultrasonography and biomarkers have been described to assess placental health and fetal viability. Pregnancy associated glycoproteins (PAGs) are produced by the ruminant placenta and are detected in maternal circulation. In cattle, changes in circulating PAG concentrations are associated with embryonic and fetal outcomes. The objective of this study was to determine the association between placentome blood perfusion and circulating PAG concentrations as they relate to the health of the developing fetus. We hypothesized that placentome perfusion and PAG concentration will be positively correlated and associated with neonatal outcome. A prospective, observational study was designed using 26 pregnant, nulliparous, Angus heifers in which PAG concentration and placentome blood perfusion were assessed throughout gestation, with assessment of calving characteristics following parturition. Placentome blood perfusion was visualized at 30-day intervals via transrectal Doppler ultrasonography with power flow function. Ultrasound images were analyzed using ImageJ software to determine the percent area of perfusion and integrated pixel densities. Venous blood was collected and PAG concentrations were determined via serum PAG enzyme-linked immunoassay. Mean placentome blood perfusion increased as gestation advanced. PAG concentrations demonstrated the expected temporal trend, increasing with gestation length, and were positively linearly correlated with placentome perfusion (P < 0.0001). The relationship identified between circulating PAG concentration and placentome blood perfusion suggests the use of transrectal power flow Doppler ultrasonography as a noninvasive technique to determine placental blood flow morphometrics to assess conceptus wellbeing throughout pregnancy.

Differences in daily milk production during early pregnancy alter placental characteristics and neonatal metabolic amino acid levels in dairy cows

We investigated the effects of differences in milk production during early pregnancy on placental characteristics at full term, calf birth weights, and their metabolic status. Thirty-four Holstein cows were categorized into three groups (Low, n = 9; Middle, n = 16; High, n = 9) based on the quartile of average daily 4% fat-corrected milk production during early pregnancy. The High group showed higher milk component production than the other groups (P < 0.05) during early and mid-pregnancy. Although most placental characteristics did not differ significantly among the groups, cows in the High group had larger individual cotyledons and fewer medium-sized cotyledons than those in the Low group (P < 0.05). Plasma amino acid concentrations of calves in the Low and High groups were significantly higher than those of calves in the Middle group, although calf birth weights were similar among the groups. Furthermore, cows in the Low group had longer dry periods than those in the High (P = 0.004) and Middle (P = 0.058) groups. This suggests that cows in the Low group may have provided more amino acids to the fetus because of low lactation and long dry periods. Conversely, cows in the High group required more energy for lactation during early pregnancy, which can reduce nutrient availability to the placenta and fetus; however, increasing individual cotyledonary sizes during late pregnancy may ensure that the same amounts of amino acids as those in cows in the Low group are supplied to the fetus, recovering the birth weights.

Differential average daily gain of pregnant Holstein × Gyr dairy heifers causes placental adaptations to support fetal growth and development

This study aimed to evaluate the effects of differential average daily gain targets of dairy heifers throughout gestation on placental hemodynamics, uterine involution, colostrum production of the heifers, and effects on newborn calf weight and immunity transfer. Fourteen Holstein × Gyr heifers with an average body weight of 446 ± 46.7 kg and age of 25 ± 3.9 mo were randomly assigned to the following treatments: moderate body weight gain (MOD, n = 7), where heifers were fed to achieve 0.50 kg/d; and high body weight gain (HIG, n = 7), where heifers were fed to achieve 0.75 kg/d. Target average daily gains were established based on common tropical dairy production systems. The heifers received a total mixed ration feed twice daily starting at 70 d of gestation. Placentome vascularization was assessed using a color Doppler ultrasound at 180, 210, and 240 d of gestation. After calving, cotyledons were counted and sampled to analyze the mRNA expression of placental angiogenesis markers. After birth, calves were weighed and fed colostrum, and transfer of passive immunity efficiency was assessed. A significant increase in cotyledons was detected for MOD placenta soon after expulsion (81.5 ± 12.91 vs. 63.6 ± 10.52). Placentome vascularization at the final third of gestation increased for MOD heifers compared with HIG. Greater mRNA expression after membrane expulsion of VEGFB and IGFR1 in cotyledons and a greater estradiol concentration in circulation 1 d before calving was found for MOD heifers compared with HIG heifers; however, uterine involution postpartum was not different between treatment groups. Greater colostrum production was observed in HIG heifers (3.9 ± 1.05 vs. 2.2 ± 1.57 L) but with lower quality (25.2 ± 0.51 vs. 29.5 ± 0.65 Brix). No differences were observed in birth weight or transfer of passive immunity efficiency between treatments; however, HIG calves had significantly greater vitality scores than MOD calves. The results of this study indicate that a moderate feeding regimen enhances placental blood flow by increasing angiogenesis, which suggests improved nutrient transfer to the fetus without major effects on its development during the neonatal stage, colostrum production, or uterine involution in the heifers.

Impact of high-fat diet consumption during prolonged period of pregnancy on placenta structures and umbilical vascular growth in goats

This study aimed to verify the impact of high-fat diet consumption for a prolonged period on oxidative stress, fetal growth, umbilical vascular system, and placental structures in pregnant goats. Twenty-two pregnant goats were grouped into the control diet (n= 11) and fat diet (n = 11). Flaxseed meal was added to the fat diet, replacing the corn grain of concentrate, from gestational day 100 to delivery date. Diets were isonitrogenous and isoenergetic, differing in fat content (2.8% vs. 6.3% dry matter). The fat group showed higher feed intake and total plasma lipid levels than the control group (P < 0.001). No difference was found in placentome, and umbilical vascular development. Fat diet-fed goats exhibited a lower systolic peak in the umbilical artery. At delivery, placental traits were similar with the exception of the cotyledon width (P = 0.0075), which was smaller in the fat group and cotyledon surface (P = 0.0047) for multiple pregnancy of fat diet. Cotyledonary epithelium showed more intense staining of lipid droplets and a greater area for lipofuscin staining in the fat group compared to control group (P < 0.001). The mean live weight of the kids was lower in the fat group in the first week after delivery than in control group. Thus, in goats, the continuous administration of a high-fat diet during pregnancy does not appear to modify the fetal-maternal vascular structures but has an impact on a part of the placental structure; therefore, its use must be carefully evaluated.

Effect of the Supplementation Using an Herbal Mixture as a Choline Source during Early Gestation in Rambouillet Ewes

Previous research indicates that adequate choline nutrition during late gestation improves fetal development. However, there is a lack of studies describing choline's role during early gestation. Thus, the current study hypothesizes that an herbal mixture as a source of choline (Biocholine) positively affects offspring development from ewes supplemented during early gestation. Therefore, the objectives were to evaluate the impact of biocholine on the programming of the offspring early in life through the evaluation of dams and newborn performance. Twenty-eight four-year-old Rambouillet ewes were assigned randomly to two treatments: non-supplementation and 4 gd^-1 of biocholine during the early gestation. Compared with the dams without supplementation, the ewes supplemented using biocholine showed no increase in parameters such as birth and weaning weight (p > 0.05). Additionally, the milk yield and quality of colostrum and milk did not present statistical differences (p > 0.05). However, the placental membrane development was reduced in the ewes that received supplementation with biocholine; interestingly, those dams increased the weight of the newborns during the lambing period (p < 0.05). Finally, the current study proposes necessary elucidation of how placental size is programmed and if less placental development has potential benefits in the fetus's development.

Effects of nutrient restriction and subsequent realimentation in pregnant beef cows: Maternal endocrine profile, umbilical hemodynamics, and mammary gland development and hemodynamics

Our hypothesis was that maternal nutrient restriction would negatively impact the endocrine and metabolic status of the pregnant cow, therefore influencing the mammary gland in preparation for lactation. We further hypothesized that earlier timing of realimentation could prevent negative impacts of nutrient restriction. The objectives were to investigate the influence of nutrient restriction and realimentation during early to late gestation on endocrine profile, umbilical hemodynamics, and mammary gland development and hemodynamics in pregnant beef cows. In Experiment 1, on d 30 of pregnancy cows (initial BW = 667.5 ± 13.4 kg, BCS = 6.2 ± 0.1) were randomly assigned to one of 3 treatments: 1) 100% NRC requirements from d 30 to 254 of gestation (CCC; n = 6); 2) 60% NRC from d 30 to 85, thereafter being re-alimented to 100% NRC to d 254 (RCC; n = 5); 3) or receive 60% NRC from d 30 to 140, thereafter being re-alimented to 100% NRC to d 254 (RRC; n = 6). Cows were returned to a common outdoor facility for calving thereafter and were fed ad libitum. In Experiment 2, on d 30 of pregnancy, cows (initial BW = 620.5 ± 11.3 kg, BCS = 5.1 ± 0.1) were randomly assigned to dietary treatments including: control (CON; 100% NRC; n = 18) and nutrient restriction (RES; 60% NRC; n = 30). On d 85 of pregnancy, cows were either slaughtered (CON, n = 6 and RES, n = 6), remained on control (CC; n = 12) and restricted (RR; n = 12) treatments, or were realimented to control (RC; n = 11). On d 140 of pregnancy, cows were either slaughtered (CC, n = 6; RR, n = 6; RC, n = 5), remained on control (CCC, n = 6; RCC, n = 5), or were realimented to control (RRC, n = 6). On d 254 of pregnancy, all remaining cows were slaughtered (CCC, n = 6; RCC, n = 5; RRC, n = 6). Mammary hemodynamics and endocrine profile were measured. Serum urea nitrogen, NEFA, as well as fetal parameters were measured in Experiment 1; whereas in Experiment 2, mammary gland development was recorded. In Experiment 1, RRC cows had lower dry matter intake (P = 0.001) and consequently lower BW change (P = 0.06). However, maternal nutrition did not alter mammary hemodynamics, hormonal patterns, and fetal characteristics (P > 0.11). In Experiment 2, CCC cows had increased (P = 0.02) mammary gland blood flow ipsilateral to the gravid horn as well as greater (P = 0.02) mammary gland fat on d 254. Nevertheless, plane of nutrition did not alter hormonal concentrations nor mammary gland characteristics (P > 0.15). These data indicate that nutrient restriction did not alter mammary hemodynamics nor endocrine profile throughout gestation.

Effect of peri-conception high fat diets on maternal ovarian function, fetal and placentome growth, and vascular umbilical development in goats

The objective of this study was to determine whether a high-fat diet (HFD) fed to goats for a brief period during peri-conception would optimize reproductive and fetal responses. Thirty-four Anglo-Nubian crossbred adult goats were allocated into three groups: control (n = 11), fed with a total mixed ration (TMR) based on chopped elephant grass and concentrate; HFBM (n = 11), given TMR supplemented with soybean oil on a 0.5% dry matter basis for 11 days starting nine days before mating (BM); and HFAM (n = 12), fed with soybean oil included in the TMR for 15 days after mating (AM). The TMR diets differed in their fat content (7.5% vs. 2.9%). All goats had estrus synchronized for 14 days BM by intravaginal administration of 60 mg MPA sponge for 12 days. Forty-eight hours BM, the sponge was removed and 0.075 mg PGF2α was applied intramuscularly. After 36 hours, 1 mL GnRH was administered intramuscularly, and goats were mated after sponge removal. The fat groups showed lower feed intake (P < 0.001) and higher cholesterol levels (P < 0.001) when HFD was administered. Doppler and B-mode ultrasound evaluations revealed a greater (P < 0.05) number of small (< 3 mm, 10 ± 0.6 vs 8 ± 0.5) and large (≥ 3 mm, 6 ± 0.4 vs 5.0 ± 0.2) follicles and intraovarian blood area (P < 0.05) in the HFBM group during sponge removal (57.6%) and mating (24.2%) than those of the no-fat group. During AM, the fat-fed groups exhibited higher glutathione peroxidase levels (P < 0.05) and a reduction (P < 0.001) in corpus luteum size (19%) and vascularized Doppler area (41%). No difference (P > 0.05) between groups was found in fetal traits, placentome, and umbilical vascular development, except for the embryonic vesicle where HFAM twin pregnancy showed a smaller size than the control (26.1 ± 3.5 cm vs 33.7 ± 2.7 cm; P < 0.01). Thus, HFD applied during peri-conception of goats has no impact on later fetal development but improved the follicular growth when given before the mating. Thus the use of HFD in periconception has no impact on fetal development but increases follicular growth before breeding time.

Factors affecting placental size in beef cattle: Maternal and fetal influences

Our objectives were to determine the effects of dam body condition score (BCS), age of dam, and calf sex on placental size and the relationships between dam body weight (BW) and calf size with placental size. Expelled placentas and calf size at birth were collected from crossbred beef heifers and cows during four experiments (n = 22 to 39/experiment). Placentas deemed complete by visual inspection were dissected; dry weights were determined for cotyledonary and intercotyledonary tissues. Mixed linear models were used to individually determine main effects of peripartum BCS category [Thin (<5), Moderate (=5), or Fleshy (≥6)], age of dam category [Primiparous (2 yr), Young (3-4 yr), or Mature (≥5 yr)], and calf sex on placental measures. Correlations were determined for placental characteristics with prepartum dam BW, gestation length, and calf size. Thin BCS dams had lower (P ≤ 0.05) cotyledonary, total placental, and average cotyledon weights and greater placental efficiency (calf birth BW/placental weight) than moderate and fleshy dams. Intercotyledonary weight was lower (P < 0.01) in thin BCS dams compared with fleshy dams. Thin and moderate BCS dams had smaller (P ≤ 0.04) calf birth BW than fleshy dams. Primiparous dams had lower (P ≤ 0.05) total placental and average cotyledon weights than young and mature dams, yet calf birth BW was unaffected (P = 0.17). Male calves were heavier (P = 0.01) than females, yet there were no differences (P ≥ 0.59) in placental weights. Calf birth BW and heart girth had moderate positive correlations (P < 0.01) and shoulder to rump length and abdominal girth had weak positive correlations (P < 0.01) with all placental weights. Dam prepartum BW and calf flank girth had moderate positive correlations (P < 0.01) with total placental weights and weak positive correlations (P < 0.01) with cotyledonary and average cotyledon weights. Intercotyledonary weight had moderate positive correlations (P < 0.01) with gestation length and calf flank girth and a weak positive correlation (P < 0.01) with dam prepartum BW. Gestation length had a weak positive correlation (P = 0.02) with total placental weight. Number of cotyledons was not correlated (P ≥ 0.28) with any dam or offspring characteristics. In conclusion, these data suggest that both maternal age and BCS affected placental size. Calf size at birth and placental weight were positively correlated, but it is still unknown which controls and signals for the growth of the other.

Nuclear and membrane progesterone receptors expression in placenta from early to late pregnancy in sheep: Effects of restricted nutrition and realimentation

Nutrient restriction and/or realimentation may affect several placental functions, such as expression of selected regulatory factors, blood flow and other processes in sheep and other species. To determine the effects of the plane of nutrition, nulliparous white face ewes (6-8 months) carrying singletons on day 50 of gestation were randomly assigned to two dietary treatments receiving 100% of National Research Council recommendations (control; C) or 60% of C (restricted; R). Two groups remained on C or R diets from day 50 until day 130. From day 90-130 another group of C fed ewes was switched to the R diet, and another group of R fed ewes was switched to the C diet. This resulted in 7 groups (n = 5-6 ewes/group): C (day 50, 90 and 130), R (day 90 and 130), CR (day 130) and RC (day 130). At these time points, placental tissues were collected for the evaluation of progesterone receptor (PGR) protein expression (whole tissue), and mRNA expression in maternal (caruncular, CAR) and fetal (cotyledon, COT) (separated tissues). Data were statistically analyzed using analysis of variance (SAS 9.4). Protein for PGRAB and PGRB isoforms was detected using immunohistochemistry in all placental tissues, but the pattern of expression differed depending on pregnancy stage and placental compartment (e.g., CAR vs COT). PGRAB protein expression, quantified using image analysis, was greater (P < 0.04) on day 50 than 90 or 130, and was not affected by plane of nutrition. In CAR and COT, PGRAB mRNA expression was greater (P < 0.05) on day 50 than 90 or 130. PGRB mRNA expression was greater (P < 0.03) in CAR on day 50 than 90 and 130, and was greatest (P < 0.02) in COT on day 50, less on day 130, and least on day 90. For the membrane progesterone receptors, PAQR7 (membrane PGR alpha) mRNA expression was greater (P < 0.05) on days 50 and 90 than 130 in CAR, and greater (P < 0.01) on days 50 than 90 and 130 in COT; PAQR8 (membrane PGR beta) was similar throughout pregnancy in CAR and COT, and PAQR5 (membrane PGR gamma) was greatest (P < 0.0001) on day 130 in COT, but similar throughout pregnancy in CAR. Plane of nutrition affected (P < 0.05) mRNA expression for all genes in CAR and COT throughout pregnancy. These data indicate that expression of PGR in ovine placenta is dependent on stage of pregnancy and plane of nutrition in sheep. The mechanisms of how diet and stage of pregnancy influences placental PGR expression and function remains to be elucidated.

Moderate nutrient restriction of beef heifers alters expression of genes associated with tissue metabolism, accretion, and function in fetal liver, muscle, and cerebrum by day 50 of gestation

We hypothesized that a moderate maternal nutrient restriction during the first 50 d of gestation in beef heifers would affect transcript abundance of genes associated with tissue metabolism, accretion, and function in fetal liver, muscle, and cerebrum. Angus-cross heifers were estrus synchronized and assigned at breeding to one of two dietary treatments (CON- 100% of nutrient requirements to gain 0.45 kg/d; RES- 60% of CON). At day 50 of gestation, 14 heifers were ovariohysterectomized, and fetal liver, muscle, and cerebrum were collected. Transcriptome analysis via RNA-seq was conducted on the Illumina HiSeq 2500 platform using 50-bp paired-end reads at a depth of 2 × 10.4M reads/sample. Bioinformatic analysis was performed using the Tuxedo Suite and ontological analysis with DAVID 6.8. For fetal liver, muscle, and cerebrum, a total of 548, 317, and 151 genes, respectively (P < 0.01) were differentially expressed, of which 201, 144, and 28 genes, respectively were false discovery rate protected (FDR; q < 0.10). Differentially expressed genes were screened for fit into functional categories of pathways or ontologies associated with known impacts on tissue metabolism, accretion, and function. In fetal liver, five functional categories of interest (n = 125 genes) were affected by nutritional treatment: metabolic pathways, protein kinase, nucleosome core, mRNA splicing, and complement/coagulation cascades, of which 105 genes were upregulated in RES. In fetal muscle, three functional categories of interest (n = 106 genes) were affected by nutritional treatment: skeletal muscle, embryogenesis, and signaling cascades, of which 64 genes were upregulated in RES. In fetal cerebrum, three functional categories of interest (n = 60 genes) were affected by nutritional treatment: hippocampus and neurogenesis, metal-binding, and cytoskeleton, of which 58 genes were upregulated in RES. These results demonstrate that a moderate maternal nutrient restriction during the first 50 d of gestation in beef heifers alters transcript abundance of genes potentially impacting tissue metabolism, accretion, and function in fetal liver, muscle, and cerebrum. Furthermore, these results indicate that affected categories are tissue-specific and moderate maternal nutrient restriction generally increases expression of genes in fetuses from RES fed dams. Finally, these data lay the foundation upon which further research that identifies phenotypic responses to changes in these pathways may be elucidated.