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PubMed2004

Rapid assessment of in vivo cholinergic transmission by amperometric detection of changes in extracellular choline levels.

Conventional microdialysis methods for measuring acetylcholine (ACh) efflux do not provide sufficient temporal resolution to relate cholinergic transmission to individual stimuli or behavioral responses, or sufficient spatial resolution to investigate heterogeneities in such regulation within a brain region. In an effort to overcome these constraints, we investigated a ceramic-based microelectrode array designed to measure amperometrically rapid changes in extracellular choline as a marker for cholinergic transmission in the frontoparietal cortex of anesthetized rats. These microelectrodes exhibited detection limits of 300 nm for choline and selectivity (> 100 : 1) of choline over interferents such as ascorbic acid. Intracortical pressure ejections of choline (20 mm, 66-400 nL) and ACh (10 and 100 mm, 200 nL) dose-dependently increased choline-related signals that were cleared to background levels within 10 s. ACh, but not choline-induced signals, were significantly attenuated by co-ejection of the acetylcholinesterase inhibitor neostigmine (Neo; 100 mm). Pressure ejections of drugs known to increase cortical ACh efflux, potassium (KCl; 70 mm, 66, 200 nL) and scopolamine (Scop; 10 mm, 200 nL), also markedly increased extracellular choline signals, which again were inhibited by Neo. Scop-induced choline signals were also found to be tetrodotoxin-sensitive. Collectively, these findings suggest that drug-induced increases in current measured with these microelectrode arrays reflect the oxidation of choline that is neuronally derived from the release and subsequent hydrolysis of ACh. Choline signals assessed using enzyme-selective microelectrode arrays may represent a rapid, sensitive and spatially discrete measure of cholinergic transmission.

Acetylcholine↗
PubMed1982

The independency of choline transport and acetylcholine synthesis.

The coupling of choline transport to acetylcholine synthesis has been investigated by measurement of the isotopic dilution of a pulse of [3H]choline during its incorporation into the recently synthesised acetylcholine of cerebral cortex synaptosomes. Recently synthesised acetylcholine was identified as that containing 14C-labelled precursors introduced by a preincubation before the pulse. When [14C]glucose was used to label acetyl-CoA coupling ratios (calculated as the inverse of the dilution of extracellular [3H]choline during its incorporation into [3H]acetylcholine) of about 0.05-0.2 were found at a choline concentration of 1 microM, rising to 0.5 at choline concentrations of 10-50 microM. Experiments using [14C]choline as a precursor gave similar results, and it was shown that the isotopic dilution did not occur extrasynaptosomally and was not affected by low glucose concentrations. Coupling ratios were always less than unity and rose as the choline concentration increased. It is concluded that choline transported into the nerve terminal has no privileged access to choline acetyltransferase. The results can be explained by a rate-controlling transport of choline into the terminal followed by its rapid acetylation rather than any linkage or coupling of the two processes.

Acetyl Coenzyme A↗
PubMed1977

Effect of two hemicholiniums on the disposition and distribution of endogenous free choline in anaesthetized rabbits.

1 The effects of hemicholinium no. 3 (HC-3) and its p-terphenyl analogue (TPHC-3) on the disposition and distribution of free choline were studied in rabbits under pentobarbitone anaesthesia. Free choline was determined by bioassay. 2 The respiration of animals given 0.35 mumol/kg of HC-3 was hardly affected; however, 4 out of 6 rabbits given the same dose of TPHC-3 exhibited varying degrees of respiratory impairment. All animals that received 2 injections (1 h apart) of either HC-3 (1.4 mumol/kg) or TPHC-3 (0.7 mumol/kg) developed respiratory difficulty about 1 h after the second injection. 3 The respiratory distress was accompanied by a 2 to 15-fold rise in plasma choline concentration. This rise has been attributed to hypoxia. 4 In experiments in which choline has been infused it was observed that HC-3 could impair the animal's ability to dispose of exogenous choline. In control rabbits neither HC-3 nor TPHC-3 produced changes in plasma choline concentrations unless the respiration was depressed. 5 Either HC-3 or TPHC-3 (both at 0.35 mumol/kg) significantly (P less than 0.05) reduced the kidney choline concentration by 40% and 30% respectively; both hemicholiniums raised the lung choline concentration by about 35%. Only TPHC-3 caused a significant rise (40%) in liver choline. The choline concentrations in other tissues were unaffected by the hemicholiniums.

Animals↗
PubMed1972

Metabolism and transfer of choline in hamster small intestine.

1. The transfer and metabolism of choline was studied with sacs of everted intestine of hamster.2. Approximately half the choline transferred from the mucosal fluid may be metabolized. High voltage electrophoresis, paper chromatography and ion exchange chromatography have been used to identify this meta bolite as betaine.3. The concentration of choline and betaine together accumulating in the gut wall and serosal fluid are greater than that of choline present initially in the mucosal fluid indicating some kind of specific mechanism for choline transport.4. A detailed analysis of choline transfer suggests that the movement of choline cannot be accounted for by simple diffusion. The concentration of choline accumulating in the gut wall and serosal fluid, the inhibitory effects of hemicholinium-3 and alpha-methylglucoside on choline transfer, and the insensitivity of betaine transfer to hemicholinium-3 suggest a specific active transport process for choline independent of active betaine transport.

Animals↗
PubMed1974

Acetylcholine synthesis from recaptured choline by a sympathetic ganglion.

1. The recapture and re-use of choline formed by the hydrolysis of released acetylcholine (ACh) was studied in the superior cervical ganglion of the cat using radioactive tracer techniques. The ganglion's ACh store was labelled by perfusion, during preganglionic nerve stimulation, with Krebs solution containing [(3)H]choline.2. Preganglionic stimulation (5 Hz for 20 min) of ganglia containing [(3)H]ACh released similar amounts of radioactivity when perfusion was with neostigmine-choline-Krebs or with hemicholinium-Krebs. This indicated that neostigmine does not increase transmitter release.3. The amount of radioactivity collected from stimulated ganglia during perfusion with choline-Krebs was 39% of the amount of radioactivity collected during perfusion with medium containing neostigmine or hemi-cholinium. This difference in release was almost (85%) accounted for at the end of the experiment by extra radioactive ACh in the ganglia perfused with choline-Krebs. It is concluded that during preganglionic nerve stimulation approximately 50-60% of endogenously produced choline is recaptured for ACh synthesis; thus, during activity preganglionic nerve terminals appear selectively to accumulate choline.4. However, chronically decentralized ganglia accumulated as much choline as did acutely decentralized ganglia, and this was interpreted as indicating that at rest preganglionic nerve terminals do not selectively accumulate choline.5. Increased exogenous choline concentration increased the amount of radioactivity collected during nerve stimulation in the absence, but not the presence, of an anticholinesterase agent. The spontaneous efflux of radioactivity was little affected by changes in external choline levels. It is concluded that exogenous choline and choline made available from released transmitter compete for uptake into nerve terminals.

Acetylcholine↗
PubMed1987

Acetylcholine metabolism and choline availability at the neuromuscular junction of mature adult and aged rats.

1. The balance between acetylcholine (ACh) synthesis and degradation and the availability of choline were studied in the neuromuscular junction of rats aged 10 (mature adult) and 28 (aged) months. Endogenous and 2H4-labelled variants of ACh and choline were assayed during steady-state stimulated and resting conditions using gas chromatography-mass spectrometry. 2. Endogenous ACh levels were 34% less per nerve terminal in the older rats; in non-innervated tissue, the levels were 12-14% as large as in innervated tissue. Endogenous choline levels in innervated and non-innervated tissue were similar and were 28% higher in the older animals. 3. Accumulation of 2H4-labelled choline was significantly greater in the 28-month animals; the specific activity at equilibrium was 60% higher in the older rats. 4. Incorporation of [2H4]choline into [2H4]ACh was significantly faster in the aged rats; times to half-maximal values were 2.0 and 0.6 min in the 10- and the 28-month animals, respectively. There was no measurable synthesis of ACh in the non-innervated tissue. 5. There were no major age-related differences in the amount of ACh released during stimulation between 1 and 20 Hz. In contrast, choline efflux during stimulation was significantly greater in the aged animals; flux values (+/- S.E. of mean) were 0.48 (+/- 0.014) and 0.66 (+/- 0.038) nmol/min for the 10- and the 28-month rats, respectively. 6. Under resting conditions, endogenous ACh efflux was significantly greater in the older rats; the rates (+/- S.E. of mean) were 2.00 (+/- 0.21) and 3.05 (+/- 0.43) pmol/min for the younger and the older animals, respectively; similarly, choline efflux was greater in the aged tissue. 7. These results indicated that lower intracellular ACh levels can be attributed to enhanced leakage rather than to decreased synthesis. Greater ACh efflux is accompanied by correspondingly greater choline uptake in the 28-month rats; this is associated with greater choline efflux and higher steady-state choline levels in the aged tissue.

Acetylcholine↗
PubMed2006

Subtype-specific inhibition of nicotinic acetylcholine receptors by choline: a regulatory pathway.

Choline is an essential nutrient and a precursor of neurotransmitter acetylcholine (ACh) and is produced at synapses during depolarization, upon hydrolysis of ACh via acetylcholinesterase, and under conditions of injury and trauma. Animal studies have shown that supplementation with choline during early development results in long-lasting improvement in memory in adults; however, the mechanisms underlying this effect are poorly defined. Previous studies revealed that choline interacts with type IA (alpha7*) nicotinic acetylcholine receptors (nAChRs) as a full agonist and as a desensitizing agent and is a weak agonist of type III (alpha3beta4*) nAChRs. Because nAChRs play a role in learning and memory and are generally inhibited by agonists at low concentrations, we investigated in this study the inhibitory effects of choline on non-alpha7 nAChRs such as type II (alpha4beta2*) and type III nAChRs. Using whole-cell patch-clamp recordings from neurons of rat hippocampal and dorsal striatal slices, we demonstrate that choline inhibited type III nAChR-mediated glutamate excitatory postsynaptic currents (EPSCs). Choline inhibited ACh-induced N-methyl-D-aspartate (NMDA) EPSCs in CA1 stratum radiatum (SR) interneurons of rat hippocampal slices with an IC50 of approximately 15 microM. Choline did not inhibit NMDA or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors in CA1 SR interneurons. Choline inhibited type II nAChRs in CA1 SR interneurons with an IC50 of approximately 370 microM. The present results reveal an order of inhibitory potency for choline type III>type IA>type II nAChRs. It is concluded that brain nAChRs, but not glutamate receptors, are the primary targets for the regulatory actions of choline.

Animals↗
PubMed1980

Choline transport in Saccharomyces cerevisiae.

Choline transport of Saccharomyces cerevisiae was measured by the filtration method with the use of glass microfiber paper. The uptake was time and temperature dependent. The kinetics of choline transport showed Michaelis behavior; an appearent Km for choline was 0.56 microM. N-Methylethanolamine, N,N-dimethylethanolamine, and beta-methylcholine were competitive inhibitors of choline transport, with Ki values of 40.1, 3.1, and 6.9 microM, respectively. Ethanolamine, phosphorylcholine, and various amino acids examined had no effect. Choline transport required metabolic energy; removal of glucose resulted in a great loss of transport activity, and the remaining activity was abolished by 2,4-dinitrophenol, carbonyl cyanide p-trifluoromethoxyphenyl hydrazone, arsenate, and cyanide. External Na+ was not required, and the transport was not effected by ionophores, valinomycin, and gramicidin D. These results indicate that S. cerevisiae possess an active choline transport system mediated by a specific carrier. This view is further supported by the isolation and characterization of a choline transport mutant. The choline transport activity in this mutant was very low, whereas the transport of L-leucine, L-methionine, D-glucose, and myo-inositol was normal. Together with the choline transport mutant, mutants defective in choline kinase were also isolated.

Biological Transport, Active↗
PubMed2004

The Sinorhizobium meliloti ABC transporter Cho is highly specific for choline and expressed in bacteroids from Medicago sativa nodules.

In Sinorhizobium meliloti, choline is the direct precursor of phosphatidylcholine, a major lipid membrane component in the Rhizobiaceae family, and glycine betaine, an important osmoprotectant. Moreover, choline is an efficient energy source which supports growth. Using a PCR strategy, we identified three chromosomal genes (choXWV) which encode components of an ABC transporter: ChoX (binding protein), ChoW (permease), and ChoV (ATPase). Whereas the best homology scores were obtained with components of betaine ProU-like systems, Cho is not involved in betaine transport. Site-directed mutagenesis of choX strongly reduced (60 to 75%) the choline uptake activity, and purification of ChoX, together with analysis of the ligand-binding specificity, showed that ChoX binds choline with a high affinity (KD, 2.7 microM) and acetylcholine with a low affinity (KD, 145 microM) but binds none of the betaines. Uptake competition experiments also revealed that ectoine, various betaines, and choline derivatives were not effective competitors for Cho-mediated choline transport. Thus, Cho is a highly specific high-affinity choline transporter. Choline transport activity and ChoX expression were induced by choline but not by salt stress. Western blotting experiments with antibodies raised against ChoX demonstrated the presence of ChoX in bacteroids isolated from nitrogen-fixing nodules obtained from Medicago sativa roots. The choX mutation did not have an effect on growth under standard conditions, and neither Nod nor Fix phenotypes were impaired in the mutant, suggesting that the remaining choline uptake system(s) still present in the mutant strain can compensate for the lack of Cho transporter.

ATP-Binding Cassette Transporters↗
PubMed1997

Brain tumors: detection with C-11 choline PET.

PURPOSE: To evaluate the effectiveness of positron emission tomography (PET) with carbon-11 choline in brain tumor imaging. MATERIALS AND METHODS: A rat glioma cell line (C6) was incubated with C-14 choline; the time course of uptake and metabolism was determined in vitro. C-11 choline was injected intravenously in tumor-bearing rats; the time course of distribution in organs was determined. C-11 choline also was injected intravenously in 20 patients (aged 6-86 years) with brain tumors and two volunteers (aged 38 and 58 years); distribution of the tracer in the brain was determined. Regional cerebral blood flow was measured by using oxygen-15 water on the same day. RESULTS: C-14 choline was metabolized to phosphoryl choline in glioma cells. The uptake of C-11 choline by glioblastoma cells was three to four times higher than that in the rat brain. All brain tumors took up more C-11 choline than did normal brain; thus, brain tumors that were not treated, as well as those that were treated with surgery or radiation therapy, were depicted. The tumor-normal brain uptake ratio of C-11 choline in brain tumor did not correlate with the O-15 water regional blood flow in the corresponding area. CONCLUSION: C-11 choline PET can depict brain tumors effectively. This method was clinically useful in patients who had undergone surgery.

Adult↗
PubMed1982

Exogenous choline augments transmission at an identified cholinergic synapse in terrestrial mollusk Limax maximus.

1. A variety of pharmacological tests indicate that the neuromuscular junction between the salivary burster neuron (SB) and the salivary duct muscle (SD) in the terrestrial mollusk Limax maximus is cholinergic. These include the effects of curare, atropine, and hexamethonium. 2. Exogenously applied choline can act both presynaptically and postsynaptically at the synapse between the SB and SD. a) When the SB-SD synapse is bathed in 30 microM choline, there is no measurable direct postsynaptic effect at the SB-SD synapse. After several hours of choline incubation, however, an increase is observed in the size of SB-elicited junction potentials recorded from the SD. b) When the synapse is bathed in 300 microM choline, a short-term decrease is seen in the amplitudes of junction potentials (JPs) recorded from the SD. This effect is interpreted as competition between choline and acetylcholine (ACh) for postsynaptic receptor sites on the SD, since the response of the denervated SD to ACh is diminished in the presence of 300 microM choline. c) After several hours incubation in 300 microM choline, the amplitudes of JPs elicited by the SB on the SD increase. 3. The long-term effect of exogenous choline is blocked by the choline-uptake inhibitor, hemicholinium 3. 4. We conclude that exogenous choline is taken up by the presynaptic terminals of the SB and converted to ACh. Transmitter output rises with growing transmitter stores, producing an increase in the size of SB-elicited JPs recorded from the SD.

Acetylcholine↗
PubMed2001

The effects of continuous and single-dose radiation on choline uptake in organotypic tissue slice cultures of rabbit hippocampus.

The objective of the present study was to determine the time-dependent course of choline uptake in mature organotypic slice cultures of rabbit hippocampal formation and to assess the effects of continuous and single high-dose irradiation on choline uptake in cultivated slices in vitro. Transverse slices of hippocampus were dynamically incubated in a cerebrospinal fluid-like culture medium for 72 h. To study the changes in choline uptake longitudinally, the slice cultures were processed with 0.1 microM [3H]-choline, and tritium accumulation was counted. Two different gamma irradiation sources (125I seeds and a clinical 60Co source) were used as representative models of interstitial radiosurgery and other radiosurgical techniques. A total dose of approximately 6000 cGy was delivered to the brain slices in one session or in a continuous, relatively low-dose rate fashion, and their effects on high-affinity choline uptake were examined. In another set of experiments with 125I, 5 microM hemicholinium-3 was used in choline uptake procedures as a competitive high-affinity choline uptake inhibitor. The results can be summarized as follows: (1) in the control group of the hippocampal tissue culture, there was a significant increase in tritium accumulation values from 0 to 48 h and a decrease thereafter; (2) continuous 125I irradiation caused a highly significant depression of the accumulation of tritium compared to that observed in the control group throughout its application for 72 h; (3) there was no significant change in the accumulation of tritium in the slices after single high-dose rate irradiation with a 60Co source; and (4) 5 microM hemicholinium significantly depressed the accumulation of tritium in both the control and the 125I-irradiated groups, and there was no longer a difference between 125I-irradiated and control groups when both groups were treated with hemicholinium. These results demonstrate that the delivery of continuous but relatively low-dose rate gamma irradiation is more efficacious than single high-dose external irradiation on high-affinity choline uptake in hippocampal nervous tissue. The results also indicate that continuous irradiation specifically affected the high-affinity energy-dependent choline uptake mechanism, whereas nonspecific choline uptake did not seem to be disturbed.

Acetylcholine↗
PubMed1986

An in vitro study of choline uptake by intestine from neonatal and adult rats.

We studied choline uptake by slices of adult and 10-day-old rat intestine which were exposed on their mucosal surface to radiolabeled choline. Both neonatal and adult intestine transported choline. Choline uptake was observed in duodenum, jejunum, ileum, and colon of the adult rat. In the small intestine, choline uptake consisted of two components: a saturable and a nonsaturable process. The kinetic variables for saturable transport (Km, Vmax) were not significantly different in adult and neonatal small intestine. Some of the transported choline was converted to phosphatidylcholine, glycerophosphocholine, phosphocholine, and betaine. However, most of the transported choline (79-85%) was not metabolized within the intestinal slice during a 15-min period. We conclude that the capacity for choline transport in the rat small intestine is present early in neonatal life. The characteristics of this transport mechanism for choline are similar in the neonate and in the adult small intestine. Neonates should therefore be able to absorb the large amounts of unesterified choline that are present in milk.

Animals↗
PubMed2006

Choline: are our university students eating enough?

Choline is an essential nutrient; dietary deficiency of choline is associated with impaired liver function, elevated blood concentrations of alanine aminotransferase, creatinine phosphokinase and homocysteine. There is also depletion of acetylcholine concentration in the brain, leading to deficit in memory function. The authors examined the dietary intake of choline in groups of students at the Mona Campus of the University of the West Indies. Sixty-two medical students (first and second years) and biochemistry students (final year) were recruited They were asked to (including amounts) record all foods and drinks consumed for three days (two weekdays and one weekend day). The sheets were collected and the amount of choline and betaine (a metabolite of choline) consumed were calculated Dietary intake of folate was also evaluated. The analysis revealed that 86.2% of the females and 90.9% of the males reported diets that delivered less daily choline than the adequate intake quoted by the Institute of Medicine of the National Academy of Sciences, USA (425-550 mg/day). The betaine consumption ranged between 25 to 620 mg/day (no adequate intake documented) and the folate consumed was more than the recommended daily allowance of folate (180-200 microg/day). The dietary intake of choline in the majority of students is below adequate intake. Although folate also serves similar functions to choline, it is unlikely that it can substitute for choline in all physiological aspects and therefore the implications of low dietary choline need further investigation.

Adult↗
PubMed2005

Effects of choline on blood metabolites associated with lipid metabolism and digestion by steers fed corn-based diets.

Ruminally cannulated steers (281 +/- 18 kg) were used to evaluate effects of choline on digestion and metabolism. Four steers were implanted with 24 mg of estradiol and 120 mg of trenbolone acetate, and four steers were not implanted. Cattle were assigned to concurrent 4 x 4 Latin squares. Dietary treatments were a 2 x 2 factorial: 0 or 4% tallow (DM basis) in corn-based diets, and 0 or 5 g/d supplemental choline administered abomasally. Blood collected before and 6 h after the initial choline infusion was used to assess acute responses to choline. Digestibility and blood metabolites were measured after adaptation to choline, as well as after an abomasal dose of 100 g of lipid. Digestibilities of dietary DM (P = 0.29) and of dietary total fatty acids (P = 0.42) were not affected by choline. Apparent digestibilities of C18:0 and C18:1 fatty acids were greater (P < 0.05) when diets contained 4% tallow. Digestibilities of fatty acids in the lipid dose were less than those in the diet, and no biologically important differences in fatty acid disappearance resulted from the treatments. No significant acute responses to choline were detected. After adaptation to choline, no important differences in plasma metabolites occurred in response to choline infusion. Plasma urea was less (P < 0.05) for implanted cattle, reflecting increased deposition of protein. Plasma cholesterol was greater (P < 0.05) for steers fed 4% tallow. Changes in plasma triglycerides in response to an abomasal lipid dose were less (P < 0.05) for steers fed 4% tallow, probably due to greater triglyceride concentrations at the time of lipid dosing. In summary, few responses to abomasally infused choline were observed in either digestion or plasma metabolites.

Animal Feed↗
PubMed1982

The effect of choline supplementation in growing pullet and laying hen diets.

Two experiments were conducted to determine the effect of choline supplementation on corn-soy-meat-based grower and laying hen diets. Diets contained 2.5% and 3% meat and bone meal in the growing and laying diets, respectively, and on chemical analysis contained 1005 and 1041 ppm of choline respectively. In the first experiment, 1000 ppm of choline were added to the basal growing and laying diets, and in the second experiment the laying diet was supplemented with 550 ppm or 1000 ppm of choline. In both trials, choline supplementation did not increase gains or feed efficiency for pullets from 8 to 20 weeks. However, choline supplementation during the laying period resulted in a statistically significant improvement of egg production and egg size. Supplementation of choline in the growing phase did not affect the laying performance. Laying performance was not improved by 2 micrograms/kg of supplementary vitamin B12 in a 1000 ppm choline supplement diet (78% vs. 76% hen-day production). In the second trial, added levels of choline (0, 500, and 1000 ppm) resulted in egg production from 24 to 64 weeks of 73, 76, and 76% hen-day production, respectively. Egg weights were 59, 61, and 61 g, respectively. This suggests that the total choline requirement of laying hens on a corn-soy-meat diet, and in absence of supplementary methionine, is greater than 1000 ppm but no more than 1500 ppm.

Animals↗
PubMed1984

Choline and methionine supplementation of layer diets varying in protein content.

Two experiments were conducted with White Leghorn laying hens to evaluate choline and methionine addition to diets containing various crude protein (CP) levels. Corn-soybean meal diets containing 25 g/kg meat and bone meal were used in all experiments. Either choline or methionine supplementation at 1.0 g/kg improved egg production and feed:egg ratio of hens fed 140 g/kg CP from 23 to 35 weeks of age in Experiment 1. The magnitude of response from methionine was significantly greater than that from choline. Egg production and feed: egg ratios were not affected by these supplements in diets containing 160 g/kg CP. Added methionine also improved egg yield and egg weight at both levels of CP, whereas choline had no effect. In Experiment 2, .5 g/kg choline or methionine increased egg weight of hens fed 140 g/kg CP from 33 to 45 weeks of age, but these supplements had no effect in diets containing 160 g/kg CP. In phase 2 of this experiment, either choline or methionine at 1.0 g/kg improved egg production and egg yield of hens fed either 150 or 130 g/kg CP from 45 to 57 weeks of age. The responses from methionine were greater than those from choline. Methionine also improved egg weight at the lower protein level, whereas choline had no effect. The results of this study indicate that laying hens respond to either dietary choline or methionine supplementation; the response to methionine was greater, however, than the response to choline.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

The folic acid requirements of starting broiler chicks fed diets based on practical ingredients. 1. Interrelationships with dietary choline.

Five experiments were conducted to evaluate the effect of dietary supplemental folic acid in starting broiler chick diets. In the first two experiments, basal diets based on corn and soybean meal contained 10 micrograms/kg vitamin B12 but no supplemental methionine or choline. Chicks showed curvilinear responses to folic acid supplementation with maximum growth and feed efficiencies from 1.45 mg/kg diet. The liver folic acid response was also curvilinear but reached a plateau at 1.70 mg folic acid/kg diet. The basal diet for three additional experiments contained soybean meal that had been washed with methanol to remove most of the choline. The basal diet contained only 750 mg/kg choline. Chicks exhibited a larger growth response to folic acid at low choline levels as evidenced by a significant folic acid by choline interaction. Choline and folic acid both increased tibia length and width. Folic acid supplementation increased but then decreased valgus deformity. Choline chloride supplementation also decreased the incidences of valgus and varus deformities and decreased bone ash, but increased the incidence of tibial dyschondroplasia. It is concluded that chicks fed practical ingredient-based diets require 1.3 mg folic acid/kg diet with low levels of choline, but only 1.2 mg folic acid/kg when choline is offered near the NRC recommended level of 1,300 mg/kg of choline.

Animals↗