Graduate Student Literature Review: Exploring choline's important roles as a nutrient for transition dairy cows

In late gestation and in the first weeks postpartum, lipid droplets accumulate in the hepatic tissue resulting in approximately 40% to 50% of the dairy cows developing hepatic lipidosis in the first weeks of lactation. Elevated concentrations of triacylglycerol in the hepatic tissue are associated with increased risk of peripartum diseases and impaired productive performance. Cows with hepatic lipidosis need to dispose the excess of hepatic triacylglycerol, but this is a slow process in the bovine liver and relies on primary mechanisms such as complete oxidation and ketogenesis because of the limited export of triacylglycerols as lipoproteins. Choline is a lipotropic compound because, among other functions, it facilitates the export of lipids from the liver. Supplementing choline as rumen-protected choline (RPC) to diets of feed-restricted dairy cows reduces the degree of triacylglycerol infiltration into the hepatic parenchyma in part by enhancing export of triacylglycerol as nascent lipoprotein. The reduced accumulation of triacylglycerol in hepatic tissue in feed-restricted cows fed RPC might affect secondary pathways involved in hepatic disposal of fatty acids such as increased cellular autophagy and lipophagy and minimize endoplasmic reticulum stress response and hepatocyte inflammation. Collectively, these effects on secondary pathways might further reduce the severity of hepatic lipidosis in cows. One of the benefits of supplementing RPC is improved fat digestibility, perhaps because choline, through phosphatidylcholines, facilitates lipid transport within the enterocyte by increasing the synthesis of chylomicrons. Finally, when supplemented during the transition period, RPC improves productive performance of cows, irrespective of their body condition, that extends well beyond the period of supplementation. This review summarizes the current understanding of hepatic lipidosis in early lactation, recapitulates the absorption, transport and metabolism of choline, and discusses its role on hepatic metabolism and gastrointestinal functions, which collectively results in improved performance in dairy cows.

Effect of rumen-protected choline on fat digestibility and lymph metabolome in dairy cows

Objectives were to determine the effects of supplementing rumen-protected choline (RPC) from an established source with low (L, 28.8%) or a prototype with less lipid coating protection and high (H, 60.0%) concentrations of choline chloride on digestibility of fat and supra-mammary lymph metabolome in feed-restricted cows. Pregnant, nonlactating Holstein cows (n = 33; 11/treatment) at mean (±standard deviation) 231 ± 4.7 days of gestation were blocked by body condition (4.23 ± 0.47) and assigned to receive 0 (CON) or 25.8 g/d of choline ion from L (L25.8) or H (H25.8). Cows were adapted to the diet and then fed-restricted to 42% of the net energy of lactation required for maintenance and pregnancy for 9 days. Intake of metabolizable methionine was maintained at 19 g/d. On Day 9, cows were fed 450 g of saturated fatty acids (SFA), and feces and blood were sampled continuously for 24 h. Supra-mammary lymph was sampled 6 h after feeding SFA and metabolome was characterized. Feeding RPC increased digestibility of fat (CON = 80.4 vs. RPC = 86.0 ± 1.9%) and reduced the concentration of haptoglobin in serum (CON = 174 vs. RPC = 77 ± 14 µg/ml) independent of source of RPC fed. Feeding RPC increased the concentrations of triacylglycerol in serum (CON = 15.1 vs. RPC = 17.8 ± 1.9 mg/dl) in feed-restricted cows after feeding SFA, and the increment tended to be greater for cows fed H25.8 than L25.8. Supplementing RPC tended to increase the concentrations of triacylglycerol (CON = 11.4 vs. RPC = 15.8 ± 3.4 mg/dl) in supra-mammary lymph. Feeding RPC increased the concentration of choline and affected the concentrations of analytes involved in metabolic pathways associated with amino acid metabolism and biosynthesis of phospholipids in lymph compared with CON. Feeding RPC, independent of source used, increased fat digestibility with some changes in lymph metabolome in cows under negative nutrient balance.

Discrimination of Lipogenic or Glucogenic Diet Effects in Early-Lactation Dairy Cows Using Plasma Metabolite Abundances and Ratios in Combination with Machine Learning

During early lactation, dairy cows have a negative energy balance since their energy demands exceed their energy intake: in this study, we aimed to investigate the association between diet and plasma metabolomics profiles and how these relate to energy unbalance of course in the early-lactation stage. Holstein-Friesian cows were randomly assigned to a glucogenic (n = 15) or lipogenic (n = 15) diet in early lactation. Blood was collected in week 2 and week 4 after calving. Plasma metabolite profiles were detected using liquid chromatography-mass spectrometry (LC-MS), and a total of 39 metabolites were identified. Two plasma metabolomic profiles were available every week for each cow. Metabolite abundance and metabolite ratios were used for the analysis using the XGboost algorithm to discriminate between diet treatment and lactation week. Using metabolite ratios resulted in better discrimination performance compared with the metabolite abundances in assigning cows to a lipogenic diet or a glucogenic diet. The quality of the discrimination of performance of lipogenic diet and glucogenic diet effects improved from 0.606 to 0.753 and from 0.696 to 0.842 in week 2 and week 4 (as measured by area under the curve, AUC), when the metabolite abundance ratios were used instead of abundances. The top discriminating ratios for diet were the ratio of arginine to tyrosine and the ratio of aspartic acid to valine in week 2 and week 4, respectively. For cows fed the lipogenic diet, choline and the ratio of creatinine to tryptophan were top features to discriminate cows in week 2 vs. week 4. For cows fed the glucogenic diet, methionine and the ratio of 4-hydroxyproline to choline were top features to discriminate dietary effects in week 2 or week 4. This study shows the added value of using metabolite abundance ratios to discriminate between lipogenic and glucogenic diet and lactation weeks in early-lactation cows when using metabolomics data. The application of this research will help to accurately regulate the nutrition of lactating dairy cows and promote sustainable agricultural development.

Rumen-Protected Choline Improves Metabolism and Lactation Performance in Dairy Cows

Choline is required for the synthesis of phosphatidylcholine, an important constituent of lipoproteins. Early lactation cows presumably synthesize insufficient phosphatidylcholine, and choline supplementation in a rumen-protected form might benefit metabolism and lactation. The objectives of this study were to determine the effects of feeding rumen-protected choline (RPC) on lactation and metabolism in dairy cows. In experiment 1, 369 nulliparous and parous Holstein cows housed in four pens per treatment were fed 12.9 g/day of choline as RPC from 25 days prepartum until 80 days postpartum. In experiment 2, 578 nulliparous cows housed in five pens/treatment were fed 12.9 g/day of choline as RPC in the last 22 days of gestation only. In both experiments, blood was sampled and analyzed for concentrations of nonesterified fatty acids (NEFAs) and glucose at 1, 14, and 21 days postpartum and of choline at 1 and 14 days postpartum. Blood from all cows was sampled and analyzed for concentrations of β-OH butyrate (BHB) at 1 and 14 days postpartum. Cows with BHB > 1.2 mmol/L were classified as having hyperketonemia. Hepatic tissue was collected from 46 cows from the eight pens in experiment 1 at 9 days postpartum and analyzed for concentrations of glycogen and triacylglycerol. Milk yield and components were measured for 80 days postpartum in experiment 1, whereas only milk yield was measured in experiment 2. The pen was the experimental unit of analysis. Supplementing RPC tended to increase dry matter intake (DMI) prepartum in experiments 1 and 2 and postpartum in experiment 1. Feeding cows with RPC increased yields of 3.5% fat-corrected milk (42.8 vs. 44.8 kg/day), energy-corrected milk (38.5 vs. 40.3 kg/day), milk fat (1.52 vs. 1.61 kg/day), and true protein (1.16 vs. 1.21 kg/day) in experiment 1. Milk yield tended to be greater with RPC (26.4 vs. 27.4 kg/day) in experiment 2. Supplementing RPC increased plasma choline concentrations on day 14 postpartum in experiment 1 (3.32 ± 0.27 vs. 4.34 ± 0.28 µM) and on day 1 in experiment 2 (3.35 ± 0.16 and 13.73 ± 0.15 µM). Treatment did not affect the concentrations of glucose, NEFAs, or BHB in plasma, but the incidence of hyperketonemia was less in multiparous cows fed RPC than those fed the control in experiment 1. Feeding cows with RPC reduced hepatic triacylglycerol content and tended to reduce the ratio of triacylglycerol to glycogen and the risk of hepatic lipidosis in cows in experiment 1. The concentrations of hepatic triacylglycerol on day 9 postpartum were inversely related to those of choline in plasma on day 1 postpartum. Feeding cows with RPC improved lactation and metabolism, but more benefits were noted when it was fed before and after calving.

Postruminal choline supply during negative nutrient balance alters components of hepatic mTOR signaling and plasma amino acids in lactating Holstein cows

Choline requirements for dairy cattle are unknown. However, enhanced postruminal supply of choline may increase flux through the methionine cycle to spare Met for other functions such as protein synthesis and phosphatidylcholine (PC) synthesis during periods of negative nutrient balance (NNB). The objective was to investigate the effects of postruminal choline supply during a feed restriction-induced NNB on hepatic abundance and phosphorylation of mTOR (mechanistic target of rapamycin)-related signaling proteins, hepatic lipidome and plasma AA. Ten primiparous rumen-cannulated Holstein cows (158 ± 24 DIM) were used in a replicated 5 × 5 Latin square design with 4 d of treatment and 10 d of recovery (14 d/period). Treatments were unrestricted intake with abomasal infusion of water, restricted intake (R; 60% of net energy for lactation requirements to induce NNB) with abomasal infusion of water (R0) or restriction plus abomasal infusion of 6.25, 12.5, or 25 g/d choline ion. Liver tissue was collected via biopsy on d 5 after infusions ended and used for Western blot analysis to measure proteins involved in mTOR signaling and untargeted lipidomics. Blood was collected on d 1 to 5 for plasma AA analysis. Statistical contrasts for protein and AA data were A0 versus R0 (CONT1), R0 versus the average of choline dose (CONT2) and tests of linear and quadratic effects of choline dose. Analysis of lipidomic data were performed with the web-based metabolomic processing tool MetaboAnalyst 5.0. Ratios of p-RPS6KB1:tRPS6KB1, p-EEF2:tEEF2, and p-EIF2:tEIF2 were greater with R (CONT1). Among those, supply of choline led to decreases in p-EEF2:tEEF2 (CONT2), p-EIF2:tEIF2 and tended to decrease p-EIF4BP1:tEIF4BP1. However, the effect was quadratic only for p-EEF2:tEEF2 and p-EIF2A:tEIF2A, reaching a nadir at 6.25 to 12.5 g/d choline ion. The ratio of p-RPS6KB1:tRPS6KB1 was not affected by supply of choline and was close to 2-fold greater at 25 g/d choline versus A0. Plasma Met concentration decreased with R (CONT1), but increased linearly with choline. Restriction also increased plasma 3-methyl-histidine (CONT1). The partial least squares discriminant analysis model of liver lipids distinguished treatments, with 13.4% of lipids being modified by treatment. One-way ANOVA identified 109 lipids with a false discovery rate ≤0.05. The largest group identified was PC species; all 35 detected decreased with R versus A0, but there were few differences among choline treatments. Overall, data suggested that dephosphorylation of EEF2 and EIF2A due to enhanced choline supply potentially helped maintain or increase protein synthesis during NNB. While activation of mTOR was not altered by choline, this idea of increased protein synthesis is partly supported by the increased circulating Met. However, enhanced postruminal choline had limited effects on the species of lipid produced during a period of NNB.

Intermediate metabolites and molecular correlates of one‑carbon and nutrient metabolism differ in tissues from Holstein fetuses

Methionine and folate cycles along with transsulfuration comprise the one‑carbon metabolism (OCM) pathway. Amino acids and other nutrients feed into OCM, which is central to cellular function. mRNA abundance, proteins (Western blotting), and metabolites (GC-MC) associated with OCM were used to characterize these mechanisms in fetal tissues. Liver, whole intestine, and semitendinosus muscle were harvested from fetuses in 6 multiparous Holstein cows (37 kg milk/d, 100 d gestation). Data were analyzed using PROC MIXED (SAS 9.4). Protein abundance of BHMT was greatest (P < 0.01) in liver suggesting active remethylation of homocysteine to methionine. This idea was supported by the greater (P < 0.05) mRNA of CBS, BHMT, MTR, SHMT1, and MAT1A (encoding OCM enzymes) in liver. The antioxidant protein GPX3 had greatest (P < 0.05) abundance in liver, whereas the glutathione-transferase GSTM1 was 5-fold greater (P < 0.05) in intestine than liver and muscle. Greatest concentrations of glycine, serine, and taurine along with lower cysteine underscored the relevance of OCM in fetal liver. Phosphoethanolamine concentration was greatest (4-fold, P < 0.05) in intestine and along with the greatest (P < 0.05) mRNA of SLC44A1 (choline transporter), CHKA, and CEPT1 underscored the importance of the CDP-choline pathway. Greatest (P < 0.05) mRNA of PPARA, CPT1A, and HMGCS2 along with lower PCK1 in liver highlighted a potential reliance on fatty acid oxidation. In contrast, greater (P < 0.05) concentration of myo-inositol in muscle and intestine suggested both tissues rely on glucose as main source of energy. Future research should address how environmental inputs such as maternal nutrition alter these pathways in fetal tissues and their phenotypic outcomes.

Appearance of choline metabolites in plasma and milk when choline is infused into the abomasum with or without methionine

Four lactating, ruminally cannulated Jersey cows, (mean ± standard deviation) 264 ± 54.2 d in milk and 484 ± 24.1 kg of body weight, were arranged in a 4 × 4 Latin square design to measure the effects of abomasal infusion of choline chloride with or without dl-Met on milk and plasma choline metabolites and plasma AA in cows fed a Met-deficient diet. Cows were randomly assigned to 1 of 4 experimental treatments: (1) control; no supplemental Met or choline (CON), (2) 13 g/d of choline ion delivered via abomasal infusion (CHO), (3) 13 g/d of Met delivered via abomasal infusion (MET), and (4) 13 g/d of choline and 13 g/d of Met delivered via abomasal infusion (CHO + MET). Cows received the same basal diet throughout the experiment, which was formulated to be deficient in Met (-5.0 g of Met using the NASEM, 2021, model). Periods were 7 d in length with d 1 to 2 serving as a wash-out period and cows being infused on d 3 to 7. Milk samples were collected twice daily on d 5 to 7 and were analyzed for fat, true protein, lactose, and choline metabolites including betaine, phosphocholine, and free choline using hydrophilic interaction liquid chromatography-tandem mass spectrometry. Blood samples were collected via venipuncture of the coccygeal vein at 1100, 1300, and 1500 h on d 7 of each period and were analyzed for free AA as well as choline metabolites. Plasma Met increased in response to Met infusion and an interaction with choline and Met infusion was observed in the plasma concentration of branched-chain AA. Cows receiving choline exhibited the greatest Cho yield in milk. Milk phosphocholine yield tended to be highest when both choline and Met were infused.

Rumen-protected choline reduces hepatic lipidosis by increasing hepatic triacylglycerol-rich lipoprotein secretion in dairy cows

Objectives were to determine the effects of supplementing rumen-protected choline (RPC) on hepatic composition and secretion of triacylglycerol-rich lipoprotein when cows were subjected to feed restriction to develop fatty liver. It was hypothesized that RPC reduces hepatic triacylglycerol by enhancing secretion of hepatic lipoprotein. Pregnant, nonlactating parous Holstein cows (n = 33) at mean (± standard deviation) 234 ± 2.2 d of gestation were blocked by body condition (3.79 ± 0.49) and assigned to receive 0 g/d (CON), 25.8 g/d choline ion from a RPC product containing 28.8% choline chloride (CC; treatment L25.8), or 25.8 g/d of choline ion from a RPC product containing 60.0% CC (H25.8). Cows were fed for ad libitum intake for the first 5 d and restricted to 41% of the net energy for lactation required for maintenance and pregnancy from d 6 to 13. Intake of metabolizable methionine was maintained at 18 g/d during feed restriction by supplying rumen-protected methionine. Hepatic tissue was sampled on d 6 and 13 and analyzed for triacylglycerol and glycogen, and mRNA expression of hepatic tissue was investigated. On d 14, cows were not fed and received a 10% solution of tyloxapol intravenously at 120 mg/kg of body weight to block hydrolysis of triacylglycerols in very low density lipoprotein (VLDL). Blood was sampled sequentially for 720 min and analyzed for concentration of triacylglycerol and total cholesterol. Lymph was sampled 6 h after tyloxapol infusion, and analyzed for concentrations of fatty acids, β-hydroxybutyrate, glucose, triacylglycerol, and total cholesterol. A sample of serum collected at 720 min after tyloxapol was assayed for the metabolome composition. The area under the curve (AUC) of serum triacylglycerol, VLDL cholesterol, and total cholesterol were calculated. Orthogonal contrasts evaluated the effect of supplementing RPC (CON vs. [1/2 L25.8 + 1/2 H25.8]) and source of RPC (L25.8 vs. H25.8). Least squares means and standard errors of the means are presented in sequence as CON, L25.8, H25.8. During feed restriction, supplementation of RPC reduced hepatic triacylglycerol (9.0 vs. 4.1 vs. 4.5 ± 0.6%) and increased glycogen contents (1.9 vs. 3.5 vs. 4.1 ± 0.2%). Similarly, supplementation of RPC increased the expression of transcripts involved in the synthesis and assembly of lipoproteins (MTTP), cellular autophagy (ATG3), and inflammation (TNFA), and reduced the expression of transcripts associated with mitochondrial oxidation of fatty acids (HADHA, MLYCD) and stabilization of lipid droplets (PLIN2). After infusion of tyloxapol, RPC increased the AUC for serum triacylglycerol (21,741 vs. 32,323 vs. 28,699 ± 3,706 mg/dL × min) and VLDL cholesterol (4,348 vs. 6,465 vs. 5,740 ± 741 mg/dL × min) but tended to reduce the concentrations of triacylglycerol in lymph (16.7 vs. 13.8 vs. 11.9 ± 1.9 mg/dL). Feeding RPC tended to increase the concentrations of 89 metabolites in serum, after adjusting for false discovery, including 3 acylcarnitines, 1 AA-related metabolite, 11 bile acids, 1 ceramide, 6 diacylglycerols, 2 dihydroceramides, 1 glycerophospholipid, and 64 triacylglycerols compared with CON. Feeding 25.8 g/d of choline ion as RPC mediated increased hepatic triacylglycerol secretion to promote lipotropic effects that reduced hepatic lipidosis in dairy cows.

Enhancing Metabolism and Milk Production Performance in Periparturient Dairy Cattle through Rumen-Protected Methionine and Choline Supplementation

For dairy cattle to perform well throughout and following lactations, precise dietary control during the periparturient phase is crucial. The primary issues experienced by periparturient dairy cows include issues like decreased dry matter intake (DMI), a negative energy balance, higher levels of non-esterified fatty acids (NEFA), and the ensuing inferior milk output. Dairy cattle have always been fed a diet high in crude protein (CP) to produce the most milk possible. Despite the vital function that dairy cows play in the conversion of dietary CP into milk, a sizeable percentage of nitrogen is inevitably expelled, which raises serious environmental concerns. To reduce nitrogen emissions and their production, lactating dairy cows must receive less CP supplementation. Supplementing dairy cattle with rumen-protected methionine (RPM) and choline (RPC) has proven to be a successful method for improving their ability to use nitrogen, regulate their metabolism, and produce milk. The detrimental effects of low dietary protein consumption on the milk yield, protein yield, and dry matter intake may be mitigated by these nutritional treatments. In metabolic activities like the synthesis of sulfur-containing amino acids and methylation reactions, RPM and RPC are crucial players. Methionine, a limiting amino acid, affects the production of milk protein and the success of lactation in general. According to the existing data in the literature, methionine supplementation has a favorable impact on the pathways that produce milk. Similarly, choline is essential for DNA methylation, cell membrane stability, and lipid metabolism. Furthermore, RPC supplementation during the transition phase improves dry matter intake, postpartum milk yield, and fat-corrected milk (FCM) production. This review provides comprehensive insights into the roles of RPM and RPC in optimizing nitrogen utilization, metabolism, and enhancing milk production performance in periparturient dairy cattle, offering valuable strategies for sustainable dairy farming practices.

Dose-dependent effects of rumen-protected choline on hepatic metabolism during induction of fatty liver in dry pregnant dairy cows

Objectives were to determine the effects of supplementing increasing amounts of choline ion on hepatic composition and mRNA abundance in pregnant dry cows subjected to a fatty liver induction protocol. Holstein cows (35 primiparous and 41 multiparous) at mean (± standard deviation) of 211 ± 9.9 days of gestation were blocked by body condition (3.59 ± 0.33) and assigned to receive 0, 6.45, 12.90, 19.35, and 25.80 g/day of choline ion as rumen-protected choline (RPC) as a top-dress for 14 days. Cows were fed for ad libitum intake on days 1 to 5 and restricted to 30% of the required net energy for lactation from days 6 to 14 of the experiment. Hepatic tissue was sampled on days 5 and 14 and analyzed for concentrations of triacylglycerol and glycogen, and mRNA abundance was investigated. Orthogonal contrasts evaluated the effects of supplementing RPC (0 g/day vs. rest), and the linear, quadratic, and cubic effects of increasing intake of choline ion from 6.45 to 25.80 g/day. Results are depicted in sequence of treatments from 0 to 25.8. During feed restriction, RPC reduced the concentration of hepatic triacylglycerol by 28.5% and increased that of glycogen by 26.1%, and the effect of increasing RPC intake on triacylglycerol was linear (6.67 vs. 5.45 vs. 4.68 vs. 5.13 vs. 3.81 ± 0.92% wet-basis). Feeding RPC during feed restriction increased abundance of transcripts involved in choline metabolism (CHKA, PLD1), synthesis of apolipoprotein-B100 (APOB100), and antioxidant activity (GPX3), and decreased the abundance of transcripts involved in hepatic lipogenesis (DGAT2, SREBF1) and acute phase response (SAA3). Most effects were linear with amount of choline fed. Changes in hepatic mRNA abundance followed a pattern of reduced lipogenesis and enhanced lipids export, which help explain the reduced hepatic triacylglycerol content in cows fed RPC. Choline exerts lipotropic effects in dairy cows by altering transcript pathways linked to hepatic lipids metabolism.

Increasing the prepartum dose of rumen-protected choline: Effects on milk production and metabolism in high-producing Holstein dairy cows

Peripartum rumen-protected choline (RPC) supplementation is beneficial for cow health and production, yet the optimal dose is unknown. In vivo and in vitro supplementation of choline modulates hepatic lipid, glucose, and methyl donor metabolism. The objective of this experiment was to determine the effects of increasing the dose of prepartum RPC supplementation on milk production and blood biomarkers. Pregnant multiparous Holstein cows (n = 116) were randomly assigned to one of 4 prepartum choline treatments that were fed from -21 d relative to calving (DRTC) until calving. From calving until +21 DRTC, cows were fed diets targeting 0 g/d choline ion (control, CTL) or the recommended dose (15 g/d choline ion; RD) of the same RPC product that they were fed prepartum. The resulting treatments targeted: (1) 0 g/d pre- and postpartum [0.0 ± 0.000 choline ion, percent of dry matter (%DM); CTL]; (2) 15 g/d pre- and postpartum of choline ion from an established product (prepartum: 0.10 ± 0.004 choline ion, %DM; postpartum: 0.05 ± 0.004 choline ion, %DM; ReaShure, Balchem Corp.; RPC1RD▸RD); (3) 15 g/d pre- and postpartum of choline ion from a concentrated RPC prototype (prepartum: 0.09 ± 0.004 choline ion, %DM; postpartum: 0.05 ± 0.003 choline ion, %DM; RPC2, Balchem Corp.; RPC2RD▸RD); or (4) 22 g/d prepartum and 15 g/d postpartum from RPC2 [prepartum: 0.13 ± 0.005 choline ion, %DM; postpartum: 0.05 ± 0.003 choline ion, %DM; high prepartum dose (HD), RPC2HD▸RD]. Treatments were mixed into a total mixed ration, and cows had ad libitum access via a roughage intake control system (Hokofarm Group). From calving to +21 DRTC, all cows were fed a common base diet and treatments were mixed into the total mixed ration (supplementation period, SP). Thereafter, all cows were fed a common diet (0 g/d choline ion) until +100 DRTC (postsupplementation period, postSP). Milk yield was recorded daily and composition analyzed weekly. Blood samples were obtained via tail vessel upon enrollment, approximately every other day from -7 to +21 DRTC, and at +56 and +100 DRTC. Feeding any RPC treatment reduced prepartum dry matter intake compared with CTL. During the SP, no evidence for a treatment effect on energy-corrected milk (ECM) yield was found, but during the postSP, RPC1RD▸RD and RPC2RD▸RD treatments tended to increase ECM, protein, and fat yields. During the postSP, the RPC1RD▸RD and RPC2RD▸RD treatments tended to increase, and RPC2HD▸RD increased, the de novo proportion of total milk fatty acids. During the early lactation SP, RPC2HD▸RD tended to increase plasma fatty acids and β-hydroxybutyrate concentrations, and RPC1RD▸RD and RPC2RD▸RD reduced blood urea nitrogen concentrations compared with CTL. The RPC2HD▸RD treatment reduced early lactation serum lipopolysaccharide binding protein compared with CTL. Overall, peripartum RPC supplementation at the recommended dose tended to increase ECM yield postSP, but no evidence was seen of an additional benefit on milk production with an increased prepartum dose of choline ion. The effects of RPC on metabolic and inflammatory biomarkers support the potential for RPC supplementation to affect transition cow metabolism and health and may support the production gains observed.

Rumen-protected choline and methionine during the periparturient period affect choline metabolites, amino acids, and hepatic expression of genes associated with one-carbon and lipid metabolism

Feeding supplemental choline and Met during the periparturient period can have positive effects on cow performance; however, the mechanisms by which these nutrients affect performance and metabolism are unclear. The objective of this experiment was to determine if providing rumen-protected choline, rumen-protected Met, or both during the periparturient period modifies the choline metabolitic profile of plasma and milk, plasma AA, and hepatic mRNA expression of genes associated with choline, Met, and lipid metabolism. Cows (25 primiparous, 29 multiparous) were blocked by expected calving date and parity and randomly assigned to 1 of 4 treatments: control (no rumen-protected choline or rumen-protected Met); CHO (13 g/d choline ion); MET (9 g/d DL-methionine prepartum; 13.5 g/d DL-methionine, postpartum); or CHO + MET. Treatments were applied daily as a top dress from ~21 d prepartum through 35 d in milk (DIM). On the day of treatment enrollment (d -19 ± 2 relative to calving), blood samples were collected for covariate measurements. At 7 and 14 DIM, samples of blood and milk were collected for analysis of choline metabolites, including 16 species of phosphatidylcholine (PC) and 4 species of lysophosphatidylcholine (LPC). Blood was also analyzed for AA concentrations. Liver samples collected from multiparous cows on the day of treatment enrollment and at 7 DIM were used for gene expression analysis. There was no consistent effect of CHO or MET on milk or plasma free choline, betaine, sphingomyelin, or glycerophosphocholine. However, CHO increased milk secretion of total LPC irrespective of MET for multiparous cows and in absence of MET for primiparous cows. Furthermore, CHO increased or tended to increase milk secretion of LPC 16:0, LPC 18:1, and LPC 18:0 for primi- and multiparous cows, although the response varied with MET supplementation. Feeding CHO also increased plasma concentrations of LPC 16:0 and LPC 18:1 in absence of MET for multiparous cows. Although milk secretion of total PC was unaffected, CHO and MET increased secretion of 6 and 5 individual PC species for multiparous cows, respectively. Plasma concentrations of total PC and individual PC species were unaffected by CHO or MET for multiparous cows, but MET reduced total PC and 11 PC species during wk 2 postpartum for primiparous cows. Feeding MET consistently increased plasma Met concentrations for both primi- and multiparous cows. Additionally, MET decreased plasma serine concentrations during wk 2 postpartum and increased plasma phenylalanine in absence of CHO for multiparous cows. In absence of MET, CHO tended to increase hepatic mRNA levels of betaine-homocysteine methyltransferase and phosphate cytidylyltransferase 1 choline, α, but tended to decrease expression of 3-hydroxy-3-methylglutaryl-coenzyme A synthase 2 and peroxisome proliferator activated receptor α irrespective of MET. Although shifts in the milk and plasma PC profile were subtle and inconsistent between primi- and multiparous cows, gene expression results suggest that supplemental choline plays a probable role in promoting the cytidine diphosphate-choline and betaine-homocysteine S-methyltransferase pathways. However, interactive effects suggest that this response depends on Met availability, which may explain the inconsistent results observed among studies when supplemental choline is fed.

One-carbon metabolism and related pathways in ruminal and small intestinal epithelium of lactating dairy cows

Physiological and environmental stresses such as the transition into lactation and heat load contribute to gastrointestinal tract (GIT) dysfunction. The nonruminant gastrointestinal tract has mechanisms to cope with pro-oxidant and pro-inflammatory stressors arising from the gut lumen or within intestinal cells. One-carbon metabolism (OCM) contributes to anti-oxidant capacity via the production of glutathione (GSH) and taurine, and the synthesis of phospholipid, creatine, and the osmolyte glycinebetaine among others. A multipronged approach was used to assess the biological relevance of OCM and closely-related pathways on GIT function in dairy cows. Ruminal papillae (Rum) and scrapings from duodenum (Duo), jejunum (Jej), and ileum (Ile) were collected at slaughter from eight multiparous Holstein cows averaging 128 ± 12 d in milk and producing 39 ± 5 kg/d. A MIXED model ANOVA with preplanned orthogonal contrasts was used for statistical analysis. Methionine adenosyl transferase 1 activity (MAT) was ~10-fold greater (P < 0.01) and cystathionine β-synthase activity doubled in Rum vs. small intestine. Total glutathione peroxidase (GPX) activity was greatest (P = 0.03) in Ile, but similar to Rum. Activity and mRNA abundance of betaine-homocysteine S-methyltransferase were undetectable. There was a 2.5-fold greater protein abundance of GPX1 (P < 0.01) and a ~2-fold greater abundance of GPX3 (P < 0.01) in Rum vs. small intestine. Among the various amino acids (AA) with roles in OCM or closely-related pathways (e.g. creatine synthesis), concentrations of arginine, aspartate, glutamine, methionine, and serine were lower (P < 0.01) in Rum vs. small intestine. Unlike AA, concentrations of OCM-related intermediates S-5'-adenosyl-homocysteine (SAH), glycinebetaine, carnitine, creatine (CRE), and cysteinesulfinic acid were greater (P < 0.01) while taurine was lower in Rum vs. small intestine. Intermediates of the folate cycle were undetectable. The fact that S-adenosylmethionine (SAM) was undetectable while MAT activity and SAH were greater in Rum suggested that availability of SAM (a methyl donor) is a key determinant of flux through the folate and methionine cycles in the GIT. Except for adenosine, concentrations of glutamate, glycine, α-ketoglutarate, hypotaurine, and GSH were lowest in Ile. Together, the data underscored unique differences in activity of one-carbon metabolism and related pathways across sections of the GIT.

Milk polar lipids composition and functionality: a systematic review

Polar lipids including glycerophospholipids and sphingophospholipids are important nutrients and milk is a major source, particularly for infants. This systematic review describes the human and bovine milk polar lipid composition, structural organization, sources for formulation, and physiological functionality. A total of 2840 records were retrieved through Scopus, 378 were included. Bovine milk is a good source of polar lipids, where yield and composition are highly dependent on the choice of dairy streams and processing. In milk, polar lipids are organized in the milk fat globule membrane as a tri-layer encapsulating triglyceride. The overall polar lipid concentration in human milk is dependent on many factors including lactational stage and maternal diet. Here, reasonable ranges were determined where possible. Similar for bovine milk, where differences in milk lipid concentration proved the largest factor determining variation. The role of milk polar lipids in human health has been demonstrated in several areas and critical review indicated that brain, immune and effects on lipid metabolism are best substantiated areas. Moreover, insights related to the milk fat globule membrane structure-function relation as well as superior activity of milk derived polar lipid compared to plant-derived sources are emerging areas of interest regarding future research and food innovations.

Urinary metabolomics reveals the biological characteristics of early pregnancy in pigs

Background

Embryo implantation in sows is an important event during pregnancy. During this process, blastocysts undergo dramatic morphologic changes, and the endometrium becomes receptive. Studies have shown that developmental changes associated with the crosstalk between peri-implantation embryos and embryo-uterine are driven by various biomolecules secreted by the endometrium and embryos. In sows, changes in the uterus are also reflected in circulating body fluids and urine. Metabolomics reveals the metabolic state of cells, tissues, and organisms. In this study, we collected urine samples from large white sows during the peri-implantation period. The levels of urinary metabolites at different periods were analyzed using ultra-performance liquid chromatography/tandem mass spectrometry (UPLC–MS/MS) analysis techniques.

Results

A total of 32 samples were collected from 8 sows during the estrus period and at each phase of early pregnancy (9, 12, and 15 days of gestation). A total of 530 metabolites were identified with high confidence in all samples. Compared with samples collected during the estrus phase, 269 differential metabolites were found in samples obtained during early pregnancy.

Conclusions

The identified metabolites included lipids and lipid-like molecules, organic acids and their derivatives, organic oxygen compounds, organoheterocyclic compounds, benzenoids, among others. Metabolites, such as choline and pregnanediol-3-glucuronide, play important roles in pregnancy in sows and other animals. These results reveal the metabolic changes in urine of sows during early pregnancy phase. The differential urinary metabolites can be used for assessing peri-implantation status in sows. Understanding these metabolic changes may promote the management of pregnant sows through various interventions such as provision of proper nutrition.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40813-022-00256-z.

Comparative metabolomics analysis of milk components between Italian Mediterranean buffaloes and Chinese Holstein cows based on LC-MS/MS technology

Buffalo and cow milk have a very different composition in terms of fat, protein, and total solids. For a better knowledge of such a difference, the milk metabolic profiles and characteristics of metabolites was investigated in Italian Mediterranean buffaloes and Chinese Holstein cows were investigated by liquid chromatography tandem-mass spectrometry (LC-MS/MS) in this study. Totally, 23 differential metabolites were identified to be significantly different in the milk from the two species of which 15 were up-regulated and 8 down-regulated in Italian Mediterranean buffaloes. Metabolic pathway analysis revealed that 4 metabolites (choline, acetylcholine, nicotinamide and uric acid) were significantly enriched in glycerophospholipid metabolism, nicotinate and nicotinamide metabolism, glycine, serine and threonine metabolism, as well as purine metabolism. The results provided further insights for a deep understanding of the potential metabolic mechanisms responsible for the different performance of Italian Mediterranean buffaloes' and Chinese Holstein cows' milk. The findings will offer new tools for the improvement and novel directions for the development of dairy industry.

Dietary rumen-protected choline supplementation regulates blood biochemical profiles and urinary metabolome and improves growth performance of growing lambs

This study aimed to assess the growth performance and blood metabolites, as well as metabolic profiles in the urine of lambs fed on dietary rumen-protected choline (RPC). Thirty-six Dorper × Hu lambs weighing approximately 20 kg were equally assigned to three groups, and fed on three diets supplemented with different RPC concentrations (0, 0.25% and 0.75%) for 45 days. Supplementation of RPC significantly increased average daily gain (ADG) and decreased feed-to-gain ratio (F/G) of lambs (p < 0.05). Dietary RPC was significantly associated with elevated plasma high-density lipoprotein (HDL) and suppressed low-density lipoprotein (LDL) levels when compared to the control group (p < 0.05). Moreover, concentrations of very-low-density lipoprotein (VLDL) exhibited an increasing trend (p = 0.065), whereas β-hydroxybutyrate (BHBA) levels decreased (p = 0.086) in plasma. Analysis of urine metabolome revealed that RPC supplementation significantly suppressed urinary concentrations of pyruvate (p < 0.05), while increased urinary concentrations of trimethylamine oxide, p-cresol, phenylacetylglycine and hippurate (p < 0.05). These findings suggest that RPC supplementation can promote weight gain, alter plasma lipid metabolism and modify urinary metabolome which is correlated with energy metabolism, lipid metabolism and intestinal microbial metabolism in lambs. In conclusion, based on our findings, we recommend 0.25% RPC as a supplement for growing lambs.

Effects of unprotected choline chloride on microbial fermentation in a dual-flow continuous culture depend on dietary neutral detergent fiber concentration

Choline is usually supplemented as ruminally protected choline chloride to prevent its degradation in the rumen, but the effects of unprotected choline on ruminal fermentation are unclear. Some research indicates a possible role of dietary fiber on microbial degradation of choline; therefore we aimed to evaluate the effects of unprotected choline chloride on ruminal fermentation and to investigate whether those effects depend on dietary neutral detergent fiber (NDF) concentration. Our hypothesis was that dietary NDF concentration would influence choline chloride effects on microbial ruminal fermentation. We used 8 fermentors in a duplicated 4 × 4 Latin square with a 2 × 2 factorial arrangement, combining 2 factors: (1) dietary NDF concentration and (2) unprotected choline chloride supplementation. Resulting treatments are (1) 30%NDF/Ctrl [30% NDF control diet without supplemental choline (Cho)]; (2) 30%NDF/Cho [30% NDF diet plus 1.9 g of choline ion per kg of dry matter (DM)]; (3) 40%NDF/Ctrl (40% NDF control diet without supplemental choline); and (4) 40%NDF/Cho (40% NDF diet plus 1.9 g of choline ion per kg of DM). Four 10-d periods were completed, each consisting of 7 d for adaptation and 3 d for collection of samples for estimation of nutrient disappearance and daily average concentrations of volatile fatty acids and NH₃-N. In addition, kinetics of pH, acetate, and propionate were evaluated at 0, 1, 2, 4, 6, and 8 h after morning feeding. On the last day of each period, bacteria pellets were harvested for ¹⁵N analysis and N metabolism. Fixed effects of dietary NDF concentration, unprotected choline chloride supplementation, and their interaction (NDF × Cho) were tested using the MIXED procedure of SAS version 9.4 (SAS Institute Inc., Cary, NC). Choline tended to increase total volatile fatty acid concentrations and decreased acetate molar proportion regardless of dietary NDF concentration, but it increased propionate molar proportion and decreased acetate to propionate ratio only with the 30% NDF diet. Supplementing choline decreased NDF disappearance regardless of dietary NDF; however, organic matter disappearance tended to be reduced only when choline was added to 40% NDF. Our data indicate that unprotected choline chloride effects on ruminal fermentation depend on dietary NDF concentration, allowing for a greater propionate synthesis without decreasing organic matter disappearance when fed with a 30% NDF diet.

Effects of Rumen-Protected Choline on Growth Performance, Carcass Characteristics and Blood Lipid Metabolites of Feedlot Lambs

Simple Summary

Choline is important for animal health, due to its involvement in the synthesis of vital molecules in the body. Several feed materials used in animal nutrition contain choline, but this naturally occurring choline is rapidly degraded in the rumen, therefore, it should be offered as rumen-protected choline (RPC) in ruminant animal species. Here we describe the results of a study that we performed with the aim of evaluating the effect of RPC on growth, carcass, and some blood metabolites in feedlot lambs. RPC supplementation did not significantly affect dry-matter intake, weight gain, gain:feed ratio, or carcass weights. Interestingly, RPC supplementation was associated with lower blood triglycerides and increased backfat thickness and yield grade, thus suggesting an effect of RPC on lipid metabolism. RPC supplementation was also associated with a reduced height to the shoulder and longissimus muscle area, suggesting an inhibitory effect of RPC on growth. The results of this study do not support the use of RPC supplementation to improve animal performance or carcass characteristics in feedlot lambs.

Abstract

Choline is an essential nutrient for animals, but dietary choline is degraded in the rumen, and thus, should be offered as rumen-protected choline (RPC) in ruminants. In this article, we investigate the effect of RPC supplementation in feedlot lambs. Forty intact male Saint Croix lambs (average: 20.3 kg, 3–4 months of age) on a high grain-low roughage base feed were randomly assigned to four treatments (0, 0.1, 0.2, and 0.3% RPC on dry-matter basis; n = 10 per group). RPC was offered for 90 days after 15 days of adaptation. RPC supplementation was not associated with significant differences in dry matter intake, weight gain, gain:feed ratio, carcass weights, and the dressing percentages. There was a linear decrease in height to the shoulder (p = 0.013) and longissimus muscle area (p = 0.051) with higher RPC levels, and a higher backfat thickness and yield grade with 0.3% RPC compared to 0.1% RPC (p < 0.05). Blood triglycerides concentrations were higher in control (0% RPC) compared to 0.3% RPC (p = 0.008). The lack of significant effects on growth performance and the results on backfat thickness and yield grade, may indicate undesirable effects associated with RPC supplementation. More research is needed to establish the needs and specific quantities of RPC supplementation in feedlot lambs.

Timing of initiation and duration of feeding rumen-protected choline affects performance of lactating Holstein cows

Objectives were to evaluate the effects of altering timing of initiating and duration of supplementing rumen-protected choline (RPC) on lactation performance in dairy cows. The hypothesis was that RPC increases yields of milk and milk components, regardless of when supplementation is initiated, and that the effects of supplementing RPC starting prepartum and continuing post-transition would be additive. Cows at 241 ± 2.2 d of gestation were blocked by parity group (49 entering lactation 2, 50 entering lactation >2) and 305-d milk yield and, within block, assigned randomly to 1 of 4 treatments arranged as a 2 × 2 factorial with 2 levels of choline in transition, from 21 d pre- to 21 d postpartum, and 2 levels of choline in post-transition, from 22 to 105 d postpartum. The 2 levels of RPC supplemented were either 0 g/d or 12.9 g/d of choline ion fed as 60 g/d of an RPC product that was top-dressed onto the total mixed ration. Thus, treatments were as follows: NN (n = 25): no choline in transition or post-transition; NC (n = 25): no choline in transition and choline in post-transition; CN (n = 25): choline in transition and no choline in post-transition; CC (n = 24): choline in transition and in post-transition. Prepartum, treatments were supplemented (mean ± SD) for the last 18.8 ± 5.7 and 19.2 ± 5.0 d of gestation in treatments with 0 or 12.9 g/d of choline ion, respectively. Supplementing RPC prepartum did not affect dry matter intake (DMI), body weight (BW), or body condition score (BCS) in the last 3 weeks of gestation. Likewise, RPC did not affect the yield or the composition of colostrum. Supplementation with RPC during transition increased fat percent by 0.02 percentage units, fat yield by 0.16 kg/d, and energy-corrected milk (ECM) by 3.1 kg/d in the first 21 d postpartum, and increased fat yield by 0.10 kg/d and ECM by 2.4 kg/d from 22 to 105 d postpartum. Supplementing RPC during transition did not affect DMI postpartum, but it improved feed efficiency, and cows produced 0.11 kg/d more ECM per kg of DMI. Changes in BW and BCS during the first 21 d postpartum did not differ between treatments. Cows fed RPC during transition had more negative net energy balance and 0.1 unit smaller BCS in the first 105 d postpartum than non-supplemented cows. Supplementing RPC in post-transition did not influence productive performance in dairy cows, and choline supplementation during transition or post-transition did not affect measures of reproduction. Collectively, supplementing RPC to supply 12.9 g/d of choline ion benefited productive performance in dairy cows when supplementation occurred during the transition period, but no additional benefit was observed from supplementing RPC past 22 d postpartum.

Urine metabolome alterations in malnutrition and the impact of glycerol or rumen-protected choline chloride supplementation in advanced pregnant ewes

The objective of this study was to explore the metabolic profiles of pregnancy malnutrition induced by feed restriction (FR) and the counteracting effects of glycerol and rumen-protected choline chloride supplementation. Two feeding trials were conducted. In the first experiment, twenty pregnant Hu sheep carrying multiple fetuses with a gestation period of 108 d were randomly divided into two groups. The ewes in the control (CON) group were offered 100 % of their nutritional requirements as recommended by the National Research Council (NRC), while the FR group was offered 30 % of feed intake of CON for 15 d. In the second experiment, eighteen pregnant Hu sheep were offered a feed intake comprising 30 % of the NRC-recommended nutritional requirements twice daily. The sheep were randomly divided into three groups: the FR group in the second experiment (FR2), with no supplementation, the glycerol (GLY) group, which received 40 ml of glycerol per d, and the rumen-protected choline chloride (RPC) group, which received 10 g of rumen-protected choline chloride per d for 9 d. In the first experiment, the urine metabolome of sixteen ewes showed significant difference between the CON group and FR group. Compared with the CON group, FR decreased the level of d-glucose, lactic acid, levoglucosan, α-ketoglutarate, phosphohydroxypyruvic acid, glucose 6-phosphate and the methyl donors, while increasing the level of pyruvate, fumaric acid and carnitines in urine. Both the GLY and RPC treatments counteracted some of these changes and modulated the urine metabolome in advanced pregnant ewes suffering from malnutrition.

Meta-analysis of the effects of supplemental rumen-protected choline during the transition period on performance and health of parous dairy cows

The objectives were to use meta-analytic methods to determine the effects of amount of supplemental choline ion as rumen-protected choline (RPC) starting prepartum on production and health of dairy cows. The literature was systematically reviewed and 21 experiments, with up to 66 treatment means and 1,313 prepartum parous cows, were included. All experiments had a treatment with no supplemental choline (0 g/d; n = 30 treatment means), and the amount of choline ion supplemented to treated cows ranged from 5.6 to 25.2 g/d (n = 36 treatment means). Duration of pre- and postpartum feeding of RPC averaged (±standard deviation) 22.0 ± 6.0 and 57.5 ± 42.2 d, respectively. Data collected included the ingredient composition and chemical analyses of pre- and postpartum diets, amount of choline ion supplemented, number of cows per treatment, frequency of health events, and the least squares means and respective standard error of the means for production responses, liver composition, and blood parameters. The concentrations of net energy for lactation and metabolizable amino acids and protein (MP) in pre- and postpartum diets were predicted for each treatment mean using National Research Council (2001). Mixed model meta-analysis was conducted including the random effect of experiment and weighting by the inverse of the standard error of the means squared. Increasing supplementation of choline ion during transition linearly increased pre- (β = 0.0184 ± 0.00425) and postpartum dry matter intake (β = 0.0378 ± 0.00974), and yields of milk (β = 0.436 ± 0.112), energy-corrected milk (ECM; β = 0.422 ± 0.0992), fat (β = 0.00555 ± 0.000793), and protein (β = 0.0138 ± 0.00378). Nevertheless, an interaction between choline and postpartum metabolizable methionine as a percent of MP (METMPPo) was observed for yields of milk, ECM, and protein because as METMPPo increased, the positive response to choline on yields of milk, ECM, and protein decreased. Supplementing choline during transition tended to reduce the risks of retained placenta and mastitis, but it had no effect on metritis, milk fever, displaced abomasum and ketosis, or the concentration of triacylglycerol in the hepatic tissue postpartum. The median amount of choline ion supplemented was 12.9 g/d and responses in postpartum dry matter intake and yields of milk, ECM, fat, and protein to that amount of supplementation were 0.5, 1.6, 1.7, 0.07, and 0.05 kg/d, respectively. No interactions were observed between supplemental choline and prepartum dietary net energy for lactation or metabolizable methionine as a percent of MP. Collectively, feeding RPC during the transition period improves performance in parous cows. Increases in yields of milk and milk components were observed in spite of pre- and postpartum diets, although the increments in milk, ECM, and protein yields with supplementing choline decreased as the concentration of methionine in postpartum diets increased. The optimum dose of choline ion was not detected, but likely it is more than the 12.9 g/d fed in most experiments evaluated in the current meta-analysis. Finally, the meta-analysis identified lack of sufficient data to understand the role of supplemental choline in nulliparous cows.

Natural Choline from Egg Yolk Phospholipids Is More Efficiently Absorbed Compared with Choline Bitartrate; Outcomes of A Randomized Trial in Healthy Adults

Choline is a vitamin-like essential nutrient, important throughout one’s lifespan. Therefore, choline salts are added to infant formula, supplements and functional foods. However, if choline is present in a natural form, e.g. bound to phospholipids, it may be more efficiently absorbed. The study’s aim was to evaluate if choline uptake is improved after consumption of an egg yolk phospholipid drink, containing 3 g of phospholipid bound choline, compared to a control drink with 3 g of choline bitartrate. We performed a randomized, double blind, cross-over trial with 18 participants. Plasma choline, betaine and dimethylglycine concentrations were determined before and up to six hours after consumption of the drinks. The plasma choline response, as determined by the incremental area under the curve, was four times higher after consumption of the egg yolk phospholipid drink compared with the control drink (p < 0.01). Similar outcomes were also observed for choline’s main metabolites, betaine (p < 0.01) and dimethylglycine (p = 0.01). Consumption of natural choline from egg yolk phospholipids improved choline absorption compared to consumption of chemically produced choline bitartrate. This information is of relevance for the food industry, instead of adding choline-salts, adding choline from egg yolk phospholipids can improve choline uptake and positively impact health.

A Meta-Analysis on the Impact of the Supplementation of Rumen-Protected Choline on the Metabolic Health and Performance of Dairy Cattle

Simple Summary

During the first weeks of lactation, dairy cows typically experience negative energy balance, leading to the mobilization of energy reserves. This predisposes early lactating cows towards metabolic diseases, such as fatty liver syndrome and ketosis. The supplementation of rumen-protected choline (RPC) is a strategy to restrict negative effects associated with negative energy balance in early lactating cows, but reported effects are inconsistent. This meta-analysis revealed that the supplementation of RPC positively affected dry matter intake, but this effect was associated with increased milk yield, thus without improving energy balance and metabolic profile of the cows.

Abstract

After parturition, cows undergo negative energy balance leading to fat mobilization, predisposing them to fatty liver syndrome and ketosis with major consequences for health and reproduction. Supplementation of rumen-protected choline (RPC) has attracted major research efforts during the last decade, assuming that choline improves liver function by increasing very low-density lipoprotein exportation from the liver, thereby improving metabolic profiles, milk production, and reproduction. However, the effects of RPC on production, health, and reproduction have been inconsistent. Therefore, the aim of this meta-analysis was to evaluate the effects of RPC supplementation, starting from d 20 (± 12.2) ante partum to d 53 (± 31.0) postpartum, on feed intake, milk production performance and metabolic profiles of dairy cows early postpartum. Data analyses from 27 published studies showed an increase in postpartal dry matter intake (from on average 19.1 to 19.9 kg/d; p < 0.01) and milk yield (from on average 31.8 to 32.9 kg/d; p = 0.03) in cows receiving RPC. Milk fat yield and milk protein yield were also increased (p ≤ 0.05), without changing milk protein and fat contents. However, no interactive effects between cow’s milk yield level and RPC-supplementation as well as no dose-dependent effects of RPC supplementation were observed. Supplementing the diet with RPC showed no effects on blood metabolites (non-esterified fatty acids, beta-hydroxybutyrate, glucose, and cholesterol), independent of the milk yield level of the cows. An effect on liver triacylglycerol contents, incidence of ketosis, and mastitis could not be confirmed across all studies included in this meta-analysis. Also, the positive effects of RPC supplementation on reproductive performance were not consistent findings. In conclusion, supplementing RPC in lactating dairy cows showed positive effects on dry matter intake which likely caused the improved milk yield. However, RPC supplementation did not improve the metabolic health status of the cows. As several factors might be related to the responses to RPC, further research is needed to explore the precise mechanisms of RPC action in lactating cows, especially with regards to feed intake improvement and its related metabolic health-promoting potential in early lactating dairy cows.

Hepatic betaine-homocysteine methyltransferase and methionine synthase activity and intermediates of the methionine cycle are altered by choline supply during negative energy balance in Holstein cows

Although choline requirements are unknown, enhanced postruminal supply may decrease liver triacylglycerol (TAG) storage and increase flux through the methionine cycle, helping cows during a negative energy balance (NEB). The objective was to investigate effects of postruminal choline supply during NEB on hepatic activity of betaine-homocysteine methyltransferase (BHMT), methionine synthase (MTR), methionine adenosyltransferase, transcription of enzymes, and metabolite concentrations in the methionine cycle. Ten primiparous rumen-cannulated Holstein cows (158 ± 24 d postpartum) were used in a replicated 5 × 5 Latin square design with 4-d treatment periods and 10 d of recovery (14 d/period). Treatments were unrestricted intake with abomasal infusion of water (A0), restricted intake (R; 60% of net energy for lactation requirements to induce NEB) with abomasal infusion of water (R0) or R plus abomasal infusion of 6.25, 12.5, or 25 g/d of choline ion. Liver tissue was collected on d 5 after the infusions ended, blood on d 1 to 5, and milk on d 1 to 4. Statistical contrasts were A0 versus R0 (CONT1) and tests of linear (L), quadratic (Q), and cubic (C) effects of choline dose. Plasma choline increased with R (CONT1) and choline (L). Although R decreased milk yield (CONT1), choline increased milk yield and liver phosphatidylcholine (PC), but decreased TAG (L). No differences were observed in plasma PC or very-low-density lipoprotein concentrations with R or choline. Activity and mRNA abundance of BHMT were greater with R (CONT1) and increased with choline (L). Although activity of MTR was lower with R (CONT1), it tended to increase with choline (L). No effect of R was detected for activity of methionine adenosyltransferase, but it changed cubically across dose of choline. Those responses were associated with linear increases in the concentrations of liver tissue (+13%) and plasma methionine concentrations. The mRNA abundance of CPT1A, SLC22A5, APOA5, and APOB, genes associated with fatty acid oxidation and lipoprotein metabolism, was upregulated by choline (Q). Overall, enhanced supply of choline during NEB increases hepatic activity of BHMT and MTR to regenerate methionine and PC, partly to help clear TAG. The relevance of these effects during the periparturient period merits further research.

Effects of abomasal infusions of fatty acids and one-carbon donors on hepatic ceramide and phosphatidylcholine in lactating Holstein dairy cows

Our objectives were to (1) determine whether the abomasal infusion of behenic acid (C22:0) elevated hepatic ceramide relative to palmitic acid (C16:0) or docosahexaenoic acid (C22:6n-3) infusion; (2) assess whether the abomasal infusion of choline chloride or l-serine elevated hepatic phosphatidylcholine (PC) in cows abomasally infused with C16:0; and (3) characterize the PC lipidome in cows abomasally infused with C22:6n-3, relative to C16:0 or C22:0 infusion. In a 5 × 5 Latin square design, 5 rumen-cannulated Holstein cows (214 ± 4.9 DIM; 3.2 ± 1.1 parity) were enrolled in a study with 6-d periods. Abomasal infusates consisted of (1) palmitic acid (PA; 98% C16:0); (2) PA + choline chloride (PA+C; 50 g/d choline chloride); (3) PA + l-serine (PA+S; 170 g/d l-serine); (4) behenic acid (BA; 92% C22:0); and (5) an algal oil rich in docosahexaenoic acid (DHA; 44% C22:6n-3). Emulsion infusates provided 301 g/d of total fatty acids containing a minimum of 40 g/d of C16:0. Cows were fed a corn silage-based diet. Milk was collected on d -2, -1, 5, and 6. Blood was collected and liver biopsied on d 6 of each period. Although we did not detect differences in milk yield, milk fat yield and content were lower in cows infused with DHA relative to PA. Plasma triacylglycerol concentrations were lower with DHA treatment relative to PA or BA. Cows infused with DHA had lower plasma insulin concentrations relative to cows infused with PA only. For objective 1, hepatic ceramide-d18:2/22:0 was highest in cows infused with BA relative to other treatments. For objective 2, plasma free choline concentrations were greater in PA+C cows relative to PA; however, we did not observe this effect with PA+S. Plasma total PC concentrations were similar for all treatments. Regarding the hepatic lipidome, a total of 18 hepatic PC were higher (e.g., PC-16:1/18:2) and 25 PC were lower (e.g., PC-16:0/22:6) with PA+C infusion relative to PA. In addition, 17 PC were higher (e.g., PC-20:3/22:5) and 21 PC were lower (e.g., PC-18:0/22:6) with PA+S infusion relative to PA. For objective 3, hepatic concentrations of many individual saturated PC (e.g., PC-18:0/15:0) were lower with DHA relative to other treatments. Hepatic concentrations of highly unsaturated PC with very-long-chain fatty acids (e.g., PC-14:0/22:6) were higher in DHA-infused cows relative to PA, PA+C, PA+S, or BA. The abomasal infusion of emulsions containing palmitic acid, palmitic acid with choline chloride or serine, behenic acid, or docosahexaenoic acid influence the hepatic ceramide and PC profiles of lactating cows.

Choline supply during negative nutrient balance alters hepatic cystathionine β-synthase, intermediates of the methionine cycle and transsulfuration pathway, and liver function in Holstein cows

Although choline requirements for cows are unknown, enhanced postruminal supply may decrease liver triacylglycerol and increase flux through the Met cycle to improve immunometabolic status during a negative nutrient balance (NNB). Our objectives were to investigate the effects of postruminal choline supply during a feed restriction-induced NNB on (1) hepatic activity cystathionine β-synthase and transcription of enzymes in the transsulfuration pathway and Met cycle; (2) hepatic metabolites in the Met cycle and the transsulfuration pathway, bile acids, and energy metabolism; and 3) plasma biomarkers of liver function, inflammation, and oxidative stress. Ten primiparous rumen-cannulated Holstein cows (158 ± 24 d postpartum) were used in a replicated 5 × 5 Latin square design with 4-d treatment periods and 10 d of recovery (14 d/period). Treatments were unrestricted intake with abomasal infusion of water, restricted intake (R; 60% of net energy for lactation requirements) with abomasal infusion of water, or R plus abomasal infusion of 6.25, 12.5, or 25 g/d choline ion. Liver tissue was collected on d 5 after infusions ended, and blood was collected on d 1, 3, and 5. Statistical contrasts were A0 versus R0 (CONT1), R versus the average of choline doses (CONT2), and tests of linear and quadratic effects of choline dose. Activity of cystathionine β-synthase was lower with R (CONT1) and decreased linearly with choline. Hepatic glutathione was not different with R or choline, but taurine tended to be greater with choline (CONT2). Betaine and carnitine were greater with R (CONT1) and further increased with choline (CONT2). Concentrations of NAD⁺ were greater with choline (CONT2). Cholic and glycol-chenodeoxycholic acids were decreased by R and choline, while taurocholic and tauro-chenodeoxycholic acids were not altered. Plasma aspartate aminotransferase and bilirubin were greater with R (CONT1) but decreased with choline (CONT2). Paraoxonase was lower with R and increased with choline (CONT2). Data suggest that enhanced supply of choline during NNB decreases entry of homocysteine to the transsulfuration pathway, potentially favoring remethylation to Met by acquiring a methyl group from betaine. As such, Met may provide methyl groups for synthesis of carnitine. Along with production data indicating that 12.5 g/d choline ion improved milk yield and liver fatty acid metabolism during NNB, the changes in blood biomarkers also suggest a beneficial effect of choline supply on liver function and oxidative stress.

Methyl donor supplementation suppresses the progression of liver lipid accumulation while modifying the plasma triacylglycerol lipidome in periparturient Holstein dairy cows

Co-supplementation of methyl donors may lower hepatic lipid content in transition cows. To define the ability of methyl donor supplementation (MDS) to reduce hepatic lipid content and modify the plasma lipidome, 30 multiparous Holstein cows (2.04 ± 0.69 lactations; 689 ± 58 kg of body weight; 3.48 ± 0.10 units of body condition score) were fed a ration with or without rumen-protected methyl donors (22 g/d of Met, 10 g/d of choline chloride, 3 g/d of betaine, 96 mg/d of riboflavin, and 1.4 mg/d of vitamin B₁₂) from d -28 before expected calving through d 14 postpartum. Cows were randomly enrolled based on predefined selection criteria (body condition score and parity). Base diets without MDS were formulated for gestation (15.4% crude protein with a predicted Lys-to-Met ratio of 3.25; 1.44 Mcal of net energy for lactation/kg of dry matter) and lactation (16.6% crude protein with a predicted Lys-to-Met ratio of 3.36; 1.64 Mcal of net energy for lactation/kg of dry matter). Blood sampling occurred from d -28 relative to expected calving through d 14 postpartum. Liver tissue was biopsied at d -28 relative to expected calving and on d 5 and 14 postpartum. In addition to routine analyses, serum AA concentrations on d 10 and 12 were quantified using mass spectrometry. Plasma triacylglycerol (TAG) and cholesteryl esters (CE) were qualitatively measured using time-of-flight mass spectrometry. Data were analyzed using a mixed model with repeated measures. Dry matter intake and milk yield were not modified by MDS. The transition from d -28 relative to expected parturition to d 14 postpartum was characterized by increased plasma fatty acid (0.15 to 0.71 mmol/L) and β-hydroxybutyrate (0.34 to 0.43 mmol/L) levels and liver lipid content (3.91 to 9.16%). Methyl donor supplementation increased the serum Met level by 26% and decreased the serum Lys-to-Met ratio by 21% on d 10 and 12, respectively. Moreover, the increase in hepatic lipid content from d 5 through 14 postpartum was suppressed with MDS relative to control (3.57 vs. -0.29%). Dietary MDS modified the TAG and CE lipidome. For example, MDS increased plasma TAG 46:3 (carbon number:double bond) by 116% relative to control cows on d 5 postpartum. Moreover, MDS tended to increase plasma CE 34:6. In contrast, MDS lowered plasma TAG 54:8 by 39% relative to control cows on d 5 postpartum. We concluded that in the absence of gains in dry matter intake and milk and milk protein yields, dietary MDS slows the progression of hepatic lipid accumulation and modifies the plasma TAG lipidome in transition cows.

Choline Regulates the Function of Bovine Immune Cells and Alters the mRNA Abundance of Enzymes and Receptors Involved in Its Metabolism in vitro

Dietary choline can impact systemic immunity, but it remains unclear whether this is primarily via direct impacts on immune cells or secondary effects of altered metabolic function. To determine whether increased choline concentrations (3.2, 8.2, 13.2 μM) in cell culture alter the function of bovine innate and adaptive immune cells, we isolated cells from dairy cows in early and mid-lactation as models of immuno-compromised and competent cells, respectively. Phagocytic and killing capacity of isolated neutrophils were linearly diminished with increasing doses of choline. In contrast, lymphocyte proliferation was linearly enhanced with increasing doses of choline. Furthermore, increasing doses of choline increased the mRNA abundance of genes involved in the synthesis of choline products (betaine, phosphatidylcholine, and acetylcholine) as well as muscarinic and nicotinic acetylcholine receptors in a quadratic and linear fashion for neutrophils and monocytes, respectively. Phagocytic and killing capacity of neutrophils and proliferation of lymphocytes were not affected by stage of lactation or its interaction with choline or LPS. In neutrophils from early lactation cows, choline linearly increased the mRNA abundance of muscarinic and nicotinic cholinergic receptors, whereas choline-supplemented monocytes from mid-lactation cows linearly increased the mRNA abundance of several genes coding for choline metabolism enzymes. These data demonstrate that choline regulates the inflammatory response of immune cells and suggest that the mechanism may involve one or more of its metabolic products.

Considering choline as methionine precursor, lipoproteins transporter, hepatic promoter and antioxidant agent in dairy cows

During the transition period, fatty liver syndrome may be caused in cows undergo negative energy balance, ketosis or hypocalcemia, retained placenta or mastitis problems. During the transition stage, movement of non-esterified fatty acids (NEFA) increases into blood which declines the hepatic metabolism or reproduction and consequently, lactation performance of dairy cows deteriorates. Most of studies documented that, choline is an essential nutrient which plays a key role to decrease fatty liver, NEFA proportion, improve synthesis of phosphatidylcholine, maintain lactation or physiological function and work as anti-oxidant in the transition period of dairy cows. Also, it has a role in the regulation of homocysteine absorption through betaine metabolite which significantly improves plasma α-tocopherol and interaction among choline, methionine and vitamin E. Many studies reported that, supplementation of rumen protected form of choline during transition time is a sustainable method as rumen protected choline (RPC) perform diverse functions like, increase glucose level or energy balance, fertility or milk production, methyl group metabolism, or signaling of cell methionine expansion or methylation reactions, neurotransmitter synthesis or betaine methylation, increase transport of lipids or lipoproteins efficiency and reduce NEFA or triacylglycerol, clinical or sub clinical mastitis and general morbidity in the transition dairy cows. The purpose of this review is that to elucidate the choline importance and functions in the transition period of dairy cows and deal all morbidity during transition or lactation period. Furthermore, further work is needed to conduct more studies on RPC requirements in dairy cows ration under different feeding conditions and also to elucidate the genetic and molecular mechanisms of choline in ruminants industry.

Choline and methionine differentially alter methyl carbon metabolism in bovine neonatal hepatocytes

Intersections in hepatic methyl group metabolism pathways highlights potential competition or compensation of methyl donors. The objective of this experiment was to examine the expression of genes related to methyl group transfer and lipid metabolism in response to increasing concentrations of choline chloride (CC) and DL-methionine (DLM) in primary neonatal hepatocytes that were or were not exposed to fatty acids (FA). Primary hepatocytes isolated from 4 neonatal Holstein calves were maintained as monolayer cultures for 24 h before treatment with CC (61, 128, 2028, and 4528 μmol/L) and DLM (16, 30, 100, 300 μmol/L), with or without a 1 mmol/L FA cocktail in a factorial arrangement. After 24 h of treatment, media was collected for quantification of reactive oxygen species (ROS) and very low-density lipoprotein (VLDL), and cell lysates were collected for quantification of gene expression. No interactions were detected between CC, DLM, or FA. Both CC and DLM decreased the expression of methionine adenosyltransferase 1A (MAT1A). Increasing CC did not alter betaine-homocysteine S-methyltranferase (BHMT) but did increase 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR) and methylenetetrahydrofolate reductase (MTHFR) expression. Increasing DLM decreased expression of BHMT and MTR, but did not affect MTHFR. Expression of both phosphatidylethanolamine N-methyltransferase (PEMT) and microsomal triglyceride transfer protein (MTTP) were decreased by increasing CC and DLM, while carnitine palmitoyltransferase 1A (CPT1A) was unaffected by either. Treatment with FA decreased the expression of MAT1A, MTR, MTHFR and tended to decrease PEMT but did not affect BHMT and MTTP. Treatment with FA increased CPT1A expression. Increasing CC increased secretion of VLDL and decreased the accumulation of ROS in media. Within neonatal bovine hepatocytes, choline and methionine differentially regulate methyl carbon pathways and suggest that choline may play a critical role in donating methyl groups to support methionine regeneration. Stimulating VLDL export and decreasing ROS accumulation suggests that increasing CC is hepato-protective.

Methionine and Choline Supply during the Periparturient Period Alter Plasma Amino Acid and One-Carbon Metabolism Profiles to Various Extents: Potential Role in Hepatic Metabolism and Antioxidant Status

The objective of this study was to profile plasma amino acids (AA) and derivatives of their metabolism during the periparturient period in response to supplemental rumen-protected methionine (MET) or rumen-protected choline (CHOL). Forty cows were fed from −21 through 30 days around parturition in a 2 × 2 factorial design a diet containing MET or CHOL. MET supply led to greater circulating methionine and proportion of methionine in the essential AA pool, total AA, and total sulfur-containing compounds. Lysine in total AA also was greater in these cows, indicating a better overall AA profile. Sulfur-containing compounds (cystathionine, cystine, homocystine, and taurine) were greater in MET-fed cows, indicating an enriched sulfur-containing compound pool due to enhanced transsulfuration activity. Circulating essential AA and total AA concentrations were greater in cows supplied MET due to greater lysine, arginine, tryptophan, threonine, proline, asparagine, alanine, and citrulline. In contrast, CHOL supply had no effect on essential AA or total AA, and only tryptophan and cystine were greater. Plasma 3-methylhistidine concentration was lower in response to CHOL supply, suggesting less tissue protein mobilization in these cows. Overall, the data revealed that enhanced periparturient supply of MET has positive effects on plasma AA profiles and overall antioxidant status.