The antiviral role of zinc and metallothioneins in hepatitis C infection.

Metallothioneins (MTs) are small, cysteine-rich proteins characterized by a high affinity for monovalent and divalent cations, such as copper and zinc. Of the four known MT isoforms, only, members of the MT 1 and 2 subfamilies are widely expressed, acting as metal chaperones whose primary role is to mediate intracellular zinc homoeostasis. Metallothioneins are potently induced by heavy metals and other sources of oxidative stress where they facilitate metal binding and detoxification as well as free radical scavenging. Metallothionein expression is well documented in the context of viral infection; however, it remains uncertain whether MTs possess specific antiviral roles or whether induction is merely a consequence of cellular stress. To better understand the role of MTs following hepatitis C virus (HCV) infection, we examined MT expression and localization in vitro and in vivo and used a siRNA knockdown approach to ascertain their antiviral efficacy. We confirmed HCV-driven MT induction in vitro and demonstrated MT accumulation in the nucleus of HCV-infected hepatocytes by immunofluorescence. Using a pan-MT siRNA to knock down all members of the MT1 and MT2 subfamilies, we demonstrate that they are mildly antiviral against the JFH1 strain of HCV in vitro (~1.4 fold increase in viral RNA, P < .05). Furthermore, the antiviral effect of zinc treatment against HCV in vitro was mediated through MT induction (P < .05). Our data suggest a potential benefit of using zinc as a low-cost adjunct to current HCV antiviral therapies and suggest that zinc may facilitate the antiviral role of MTs against other viruses.

IFNL3/4 genotype is associated with altered immune cell populations in peripheral blood in chronic hepatitis C infection.

Single-nucleotide polymorphisms near the interferon lambda 3 (IFNL3) gene predict outcomes to infection and anti-viral treatment in hepatitis C virus (HCV) infection. To identify IFNL3 genotype effects on peripheral blood, we collected phenotype data on 400 patients with genotype 1 chronic hepatitis C (CHC). The IFNL3 responder genotype predicted significantly lower white blood cells (WBCs), as well as lower absolute numbers of monocytes, neutrophils and lymphocytes for both rs8099917 and rs12979860. We sought to define the WBC subsets driving this association using flow cytometry of 67 untreated CHC individuals. Genotype-associated differences were seen in the ratio of CD4CD45RO+ to CD4CD45RO-; CD8CD45RO+ to CD8CD45RO-, NK CD56 dim to bright and monocyte numbers and percentages. Whole blood expression levels of IFNL3, IFNLR1 (interferon lambda receptor 1), IFNLR1-mem (a membrane-associated receptor), IFNLR1-sol (a truncated soluble receptor), MxA and T- and NK (natural killer) cell transcription factors TBX21, GATA3, RORC, FOXP3 and EOMES in two subjects were also determined. CHC patients demonstrated endogenous IFN activation with higher levels of MxA, IFNLR1, IFNLR1-mem and IFNLR1-sol, and IFNL3 genotype-associated differences in transcription factors. Taken together, these data provide evidence of an IFNL3 genotype association with differences in monocyte, T- and NK cell levels in the peripheral blood of patients with CHC. This could underpin genotype associations with spontaneous and treatment-induced HCV clearance and hepatic necroinflammation.

Hepatic metallothionein expression in chronic hepatitis C virus infection is IFNL3 genotype-dependent.

The IFNL3 genotype predicts the clearance of hepatitis C virus (HCV), spontaneously and with interferon (IFN)-based therapy. The responder genotype is associated with lower expression of interferon stimulated genes (ISGs) in liver biopsies from chronic hepatitis C patients. However, ISGs represent many interacting molecular pathways, and we hypothesised that the IFNL3 genotype may produce a characteristic pattern of ISG expression explaining the effect of genotype on viral clearance. For the first time, we identified an association between a cluster of ISGs, the metallothioneins (MTs) and IFNL3 genotype. Importantly, MTs were significantly upregulated (in contrast to most other ISGs) in HCV-infected liver biopsies of rs8099917 responders. An association between lower fibrosis scores and higher MT levels was demonstrated underlying clinical relevance of this association. As expected, overall ISGs were significantly downregulated in biopsies from subjects with the IFNL3 rs8099917 responder genotype (P=2.38 × 10(-7)). Peripheral blood analysis revealed paradoxical and not previously described findings with upregulation of ISGs seen in the responder genotype (P=1.00 × 10(-4)). The higher MT expression in responders may contribute to their improved viral clearance and MT-inducing agents may be useful adjuncts to therapy for HCV. Upregulation of immune cell ISGs in responders may also contribute to the IFNL3 genotype effect.

Vancomycin-associated drug reaction with eosinophilia and systemic symptoms syndrome.

Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is a rare but potentially life-threatening multi-system disorder characterised by the delayed onset of fever, rash and internal organ involvement following the administration of a drug. We report three definite cases of vancomycin-associated DRESS syndrome occurring and review the literature regarding this syndrome.

A STAT4 variant increases liver fibrosis risk in Caucasian patients with chronic hepatitis B.

BACKGROUND: Host genetic modifiers of the natural history of chronic hepatitis B (CHB) remain poorly understood. Recently, a genome-wide association study (GWAS)-identified polymorphism in the STAT4 gene that contributes to the risk for hepatocellular carcinoma (HCC) was shown to be associated with the full spectrum of hepatitis B virus (HBV) outcomes in Asian patients. However, the functional mechanisms for this effect are unknown and the role of the variant in modulating HBV disease in Caucasians has not been investigated. AIMS: To determine whether STAT4 genetic variation is associated with liver injury in Caucasian patients with CHB and to investigate potential mechanisms mediating this effect. METHODS: STAT4 rs7574865 was genotyped in 1085 subjects (830 with CHB and 255 healthy controls). STAT4 expression in liver, PBMCs and NK cells, STAT4 phosphorylation and secretion of interferon-gamma (IFN-γ) according to STAT4 genetic variation was examined. RESULTS: STAT4 rs7574865 genotype was independently associated with hepatic inflammation (OR: 1.42, 95% CI: 1.07-2.06, P = 0.02) and advanced fibrosis (OR: 1.83, 95% CI: 1.19-2.83, P = 0.006). The minor allele frequency of rs7574865 was significantly lower than that in healthy controls. rs7574865 GG risk carriers expressed lower levels of STAT4 in liver, PBMCs and in NK cells, while NK cells from patients with the risk genotype had impaired STAT4 phosphorylation following stimulation with IL-12/IL-18 and a reduction in secretion of IFN-γ. CONCLUSION: Genetic susceptibility to HBV persistence, hepatic inflammation and fibrosis in Caucasians associates with STAT4 rs7574865 variant. Downstream effects on NK cell function through STAT4 phosphorylation-dependent IFN-γ production likely contribute to these effects.

The effects of West Nile virus on major histocompatibility complex class I and II molecule expression by Lewis rat Schwann cells in vitro.

The expression of major histocompatibility complex (MHC) class I and II molecules by Lewis rat Schwann cells after infection with West Nile virus (WNV) in vitro was examined by fluorescence microscopy and flow cytometry. WNV enhanced the expression of MHC class I molecules and induced the expression of MHC class II molecules by Schwann cells. Irradiated medium from WNV-infected Schwann cell cultures upregulated class I molecule expression on dissociated Schwann cell cultures but did not induce the expression of class II molecules. This finding has implications for virally triggered autoimmune diseases of nervous tissue.

Multi-drug resistant Pseudomonas aeruginosa outbreak in a burns unit--an infection control study.

A newly introduced, multi-drug resistant (MDR) strain of Pseudomonas aeruginosa was isolated from four patients admitted to the Concord Hospital Burns Unit (BU) between December 1997 and March 1998. It was the cause of recurrent episodes of bacteraemia in two. This strain was resistant in vitro to gentamicin, piperacillin and ciprofloxacin. The isolates were confirmed as a clonal strain by pulse field gel electrophoresis (PFGE). Multiple environmental swabs were taken to search for an environmental reservoir, but no source was identified. Random cultures of staff members' hands failed to demonstrate ongoing carriage. In the absence of a demonstrable point source for the outbreak, direct cross-transmission patient to patient, via transient staff hand contamination, was the most likely route of infection. Following study commencement no new cases of infection with the MDR strain were detected. It would appear that the infection cycle has been interrupted, and the outbreak terminated following the discharge of the last infected patient from the BU. Contamination of a neutral detergent in the BU with Klebsiella oxytoca was detected incidentally during environmental surveillance. A potential hospital-wide outbreak was averted.

Impact of feeding regimen on behavioral and physiological indicators for feeding motivation and satiety, immune function, and performance of gestating sows.

The effect of daily or interval (every 3 d) feeding on body weight change, blood glucose and cholecystokinin (CCK) concentrations, immune function, and behavioral activity were determined during the gestation period of sows. Sows were fed a corn-soybean meal diet either 2 kg daily or 6 kg once every 3rd d (interval). Body weight changes for the 42-d trial period were not different (P > .05) between regimens. Blood glucose concentrations were similar before feeding (P > .05). Two hours after feeding, glucose concentrations increased in interval-fed sows but not in daily-fed sows (P < .05). Premeal plasma CCK concentrations were greater for daily-fed sows than for interval-fed sows (P < .05). The CCK concentrations in sows of both regimens increased after feeding above premeal levels (P < .05), and interval-fed sows exhibited higher concentrations than daily-fed sows (P < .05). Immune function as evaluated through mitogen-induced proliferation of T cells was greater in daily-fed sows than in interval-fed sows (P < .05). Daily-fed sows were more active overall and on any given day than interval-fed sows (P < .05) and thus seemed to expend more energy. Further, daily-fed sows exhibited higher levels of mouth-based activities (i.e., sham chewing, licking, appetitive and consummatory feeding behavior, and excess drinking) than sows restricted to consumption of one large meal every 3rd d. These indicators suggest that feeding motivation significantly affected overall performance of sows. This study emphasizes the need for evaluating the impact of feeding regimens and meal size on feeding motivation and, ultimately, on the well-being of the gestating sows.

Effect of soybean variety and processing on growth performance of young chicks and pigs.

The objective of this study was to determine whether soybeans without the Kunitz trypsin inhibitor and lectins could be fed effectively to young chicks and pigs. Specifically, we compared the growth performance of chicks and pigs fed diets containing modified soybeans: Kunitz trypsin inhibitor-free (KF), lectin-free (LF), lectin and Kunitz trypsin inhibitor-free (LFKF), conventional soybeans (CSB), and commercially obtained, dehulled, solvent-extracted soybean meal (SBM). A 7-d chick experiment was conducted to evaluate the nutritional value of CSB, KF, LF, LFKF, and SBM. The experiment was conducted as a completely randomized design, with four replicates, five treatments, and six male chicks per pen (n = 120). The five treatments consisted of 23% CP dextrose-soybean-based diets containing KF, LF, LFKF, CSB, or SBM as the source of dietary protein. A 28-d pig experiment was conducted to evaluate the nutritional value of CSB, LF, LFKF, and SBM. Pens of four pigs were assigned randomly to a control, corn-SBM, or one of six corn-soybean diets containing raw or extruded soybean varieties as a 2 x 3 factorial arrangement of treatments in a randomized complete block design with five blocks per treatment (n = 140). Chicks fed diets containing any of the raw soybean varieties gained less weight (P < 0.05) than chicks fed SBM (22.81 g/d for SBM vs. 14.17 g/d for the raw soybeans combined). Among the raw soybean treatments, there was a greater effect on growth performance (P < 0.05) by removing both lectins and Kunitz trypsin inhibitor (ADG of 16.56 g for LFKF) than by removing each antinutritional factor separately (ADG of 14.38 and 14.11 g for KF and LF, respectively). Pig growth performance was different (P < 0.001) for SBM (ADG of 409 g) and all the varieties when extruded (ADG of 450 g for CSB, 417 g for LF, and 408 g for LFKF) compared with the raw soybean treatments (ADG of 101 g for CSB, 165 g for LF, and 266 g for LFKF). Among the raw soybean treatments, growth performance improved (P = 0.003) as the antinutritional factor, lectin, was removed from the soybean and improved further (P = 0.045) when both lectins and Kunitz trypsin inhibitor were removed. The growth-inhibiting effect of feeding modified soybeans to young animals was more detrimental for pigs than for chicks in our experiments. Soybeans without the Kunitz trypsin inhibitor and lectins cannot be fed successfully to young chicks and pigs without heating.

Dietary formulation with rendered spent hen meals on a total amino acid versus a digestible amino acid basis.

Previous results indicated that performance of chicks fed a high level (15%) of rendered spent hen meal (SHM) was lower than performance of chicks fed a corn-soybean meal (SBM) diet. The latter difference was hypothesized to be due to variation in digestible amino acid (AA) levels among the diets. This study evaluated diets containing SHM formulated on an equivalent total AA basis vs an equivalent digestible AA basis compared to a corn-SBM diet. Three SHM (A, B, and C), produced in commercial rendering plants, were evaluated. Mean true digestibility coefficients (percentages) for 17 AA in SHM A, B, and C were 73.1, 63.4, and 75.5, respectively. In two chick trials, 1-wk-old New Hampshire x Columbian male chicks were fed from 8 to 20 d of age a corn-SBM diet or diets containing 15% SHM formulated to be equal in total or digestible AA to the corn-SBM diet. All diets contained 21.5% CP and 3,200 kcal TME(n)/kg. Chicks fed 15% SHM (A, B, or C) diets formulated on a total AA basis had significantly lower (P < 0.05) weight gain and feed efficiency than chicks consuming the corn-SBM diet. Formulating diets containing SHM B or SHM C on a digestible AA basis yielded growth performance equivalent to chicks fed the corn-SBM diet. Growth performance of chicks fed the SHM A diet formulated on a digestible AA basis was greater (P < 0.05) than that obtained from the SHM A diet formulated on a total AA basis but was still lower than performance of chicks consuming the corn-SBM diet. Additional AA and energy supplementation of the SHM A diet formulated on a digestible AA basis only partially alleviated the latter performance difference. The results of this study indicated that formulation of diets containing SHM on a digestible AA basis is superior to formulation on a total AA basis and that 15% inclusion of two of the three SHM in chick diets had no detrimental effects on performance if the diets were formulated to contain adequate levels of digestible AA.

Effect of presolvent extraction processing method on the nutritional value of soybean meal for chicks.

This study evaluated the effect of extruding or expander processing prior to solvent extraction on the nutritional value of soybean meal (SBM). Three samples of SBM containing 100% nonexpander SBM, 100% expander SBM, or a mixture of nonexpander and expander SBM were obtained from a commercial plant. An experiment was conducted using Peterson x Hubbard commercial male broiler chicks fed 20% CP corn-SBM-corn gluten meal diets from 8 to 21 d of age. The experiment had a 3 x 2 x 2 factorial design, with three SBM types, two levels of Met + Cys (0.77 and 0.90%), and two levels of Lys (0.95 and 1.20%). Processing method had no effect on the amino acid concentration or protein solubility of the SBM. Dietary treatment had no significant effect on chick weight gain or feed intake. Feed efficiency was significantly improved (P < 0.05) by Met and Lys supplementation, but SBM processing method had no significant effect. The results of this study indicate that presolvent processing method (expander or nonexpander) had no significant effect on the nutritional value of SBM for broiler chicks.

Impact of galactose, lactose, and Grobiotic-B70 on growth performance and energy utilization when fed to broiler chicks.

Three chick assays were conducted to determine the effect of increasing dietary galactose (GAL), lactose (LAC), and Grobiotic-B70, a LAC fermentation product, on growth performance, toxicity, and energy utilization when fed to commercial broiler chicks. One-day-old male commercial broiler chicks were randomly assigned to treatments in each assay. In all assays, a 22% CP corn-soybean meal-dextrose basal diet containing a growth-promoting antibiotic (Bacitracin methylene disalicylate) was fed. In assay 1, GAL was added at 2, 4, 6, 10, or 15%. In assay 2, Grobiotic-B70 was added at 5%. In assay 3, GAL, LAC, and Grobiotic-B70 were each added at 2, 4, and 6%. All additions were made in place of dextrose, and diets were fed from 0 to 20 or 21 d of age. In assay 1, the 15% GAL treatment resulted in high mortality (27%) by d 3 and was terminated. The 10% GAL treatment also resulted in increased mortality, most of which occurred during the 7-to-14-d period. Inclusion of 2 and 4% GAL resulted in an improvement (P < 0.05) in growth compared to the basal diet. Inclusion of 2, 4, 6, and 10% GAL resulted in a significant linear decrease in MEn (r2 = 0.85). In chick assay 2, 5% Grobiotic-B70 increased growth during the first 2 wk. In chick assay 3, 6% Grobiotic increased weight gain (P < 0.05) from 0 to 14 d, and addition of 2 or 4% GAL, 2 or 4% LAC, and 4 or 6% Grobiotic-B70 increased weight gain (P < 0.08) from 0 to 21 d. Our results indicate that levels of 10 to 15% GAL are toxic. In contrast, low levels of GAL and Grobiotic-B70, and possibly LAC, may increase growth of commercial broiler chicks.

Nutritional evaluation of lectin-free soybeans for poultry.

This study evaluated the nutritional value of raw lectin-free soybeans in comparison with raw Kunitz trypsin inhibitor-free soybeans, raw conventional soybeans, and commercial heat processed soybean meal (SBM). Analyzed lectin values (milligrams per kilogram) were 7.2, 7.1, and < 0.00015 for the Kunitz-free, conventional, and lectin-free soybeans, respectively. Three experiments were conducted using New Hampshire x Columbian male chicks fed 23% CP dextrose-soybean diets from 8 to 17 d of age. Growth performance of chicks fed lectin-free soybeans was greater (P < 0.05) than that of chicks fed raw conventional soybeans in all three experiments. However, performance of chicks fed lectin-free soybeans was lower than that of chicks fed Kunitz-free soybeans or SBM. The SBM yielded weight gains and feed efficiencies that were much higher than those observed from any of the raw soybeans. True amino acid digestibility and TMEn of the lectin-free and conventional soybeans were determined using the precision-fed cecectomized rooster assay. Seven roosters were crop-intubated with 30 g of soybeans and excreta were collected for 48 h. Digestibility coefficients of most amino acids for lectin-free soybeans were 5 to 8 percentage units higher than those for conventional soybeans, but the differences were not significant (P > 0.05). Likewise, the TMEn for lectin-free soybeans was 11% higher than that for raw conventional soybeans (3.577 vs 3.227 kcal/g DM) but the difference was not significant (P > 0.05). The results of this study indicate that the nutritional value of raw lectin-free soybeans is greater than raw conventional soybeans but is less than raw Kunitz-free soybeans and SBM, suggesting that trypsin inhibitor is a greater antinutritional factor than lectins.

Phytase effects on amino acid digestibility in molted laying hens.

Two hundred sixteen previously molted Dekalb Delta Leghorn laying hens (78 wk of age) were utilized to determine the effect of phytase on the ileal digestibility of amino acids. The hens were randomly arranged in a 3 x 2 factorial to evaluate three diet types that were corn-soybean meal (C-SBM), C-SBM-meat and bone meal (C-SBM-MBM), and C-SBM-wheat middlings (C-SBM-WM) and two levels of phytase (0 or 300 U/kg of diet). Each treatment was administered to four replicates of nine hens per replicate. Hens were fed the experimental diets for 21 d, and daily egg production and feed intake were recorded. After 21 d, the hens were euthanized, and ileal contents were collected for amino acid and digestible energy determination. Egg production of the hens did not differ among the treatments (P > 0.05). A significant interaction between diet type and phytase level for Ala, Gly, Leu, and Met was observed. The interaction resulted because phytase numerically increased amino acid digestibilities for the C-SBM-MBM and C-SBM-WM diets, but phytase addition numerically decreased the amino acid digestibilities for the C-SBM diet. Diet type had a significant effect on digesibilites of most amino acids. The latter effect was due primarily to lower amino acid digestibilities for the C-SBM-MBM diet than the C-SBM-WM diet. Phytase had no significant affect on digestibility of any amino acid. Ieal digestible energy was significantly affected by diet type but not by phytase. In conclusion, diet type had a significant effect on apparent ileal amino acid digestibility and digestible energy, but phytase had no consistent effect.

Evaluation of protein and energy quality of rendered spent hen meals.

This study evaluated three spent hen meals (SHM) that were produced in commercial rendering plants. The levels (percentage) of selected nutrients (mean and range) in the meals were: CP, 64 (56 to 71); ash, 16 (12 to 18); lysine, 4.0 (3.6 to 4.3); methionine, 1.3 (1.2 to 1.4); cystine, 1.1 (0.8 to 1.5). Protein efficiency ratios (PER; weight gain per unit of protein intake) were determined in chicks fed 10% CP diets containing a SHM as the only source of dietary protein. The PER values for the SHM averaged 1.6 but varied from 1.1 to 2.2. An experiment was conducted using New Hampshire x Columbian chicks during the 7 to 20 d age period to determine the effect of substitution with either 7.5 or 15% of a SHM to a 21.5% CP corn-soybean meal diet. When substituted at 7.5%, growth performance was not affected by two of the SHM but was depressed by the other one. Growth performance was decreased by all SHM when substituted at 15% of the diet. True amino acid digestibility and TMEn of the SHM were determined using the precision-fed cecectomized rooster assay in which four roosters were crop-intubated with 30 g of a SHM and excreta were collected for 48 h. True amino acid digestibility varied among SHM (P < or = 0.05) and digestibility of cystine was substantially lower than digestibility of the other amino acids. Mean TMEn (kilocalories per gram of DM) of the SHM was 3.003 but varied by 44% among samples. The results of this study indicated that SHM has substantial nutritional value for poultry but the nutritional quality may vary greatly among samples.

Evaluation of nonfeed removal methods for molting programs.

An experiment was conducted using 336 White Leghorn hens (60 wk of age) randomly assigned to one of four treatments that consisted of feed removal for 4 or 10 d or no feed removal with ad libitum access to 95% corn or 95% wheat middlings molt diets that contained supplemental minerals and vitamins. At the end of the 4- or 10-d feed removal period, hens on these treatments were provided with the corn molt diet for 24 or 18 d, respectively. Hens on the corn or wheat middlings treatments were fed the diets for 28 d. At d 28, hens on all treatments were fed a corn-soybean meal (16% CP) layer diet for 40 wk (64 to 104 wk of age). Both feed removal and the wheat middlings treatments resulted in total cessation of egg production within 8 d. Egg production of hens fed the corn molt diet had decreased to 3% by d 28. Body weight loss for hens fed the corn or wheat middlings diet was approximately 15 and 8% at d 28, respectively. Hens fed the wheat middlings diet returned to production slightly faster than hens on the other treatments. Postmolt egg production and egg mass (wk 5 to 44) were generally higher for the wheat middlings and 10-d feed removal treatments than for the corn or 4-d feed removal treatments. There were no consistent differences in mortality, egg weight, egg specific gravity, feed efficiency, and layer feed consumption among treatments. This research indicates that diets with high corn or wheat middlings, particularly wheat middlings, are effective nonfeed removal methods for molting hens.

Bioavailability of lysine from a liquid lysine source in chicks.

Two experiments were conducted to assess the bioavailability of lysine from a liquid lysine product (LLP; 60% lysine) relative to crystalline L-lysine.HCl. In the first experiment, four groups of five chicks were fed a lysine-deficient basal diet containing corn, soybean meal, and feather meal or the basal diet supplemented with 0.1 or 0.2% lysine from L-lysine.HCl or LLP from Day 8 to 22 posthatching. Weight gain and feed efficiency responded linearly (P < 0.01) to increasing levels of lysine from either lysine source, and multiple linear regression analysis of weight gain regressed on supplemental lysine intake indicated no difference (P > 0.05) in the response to lysine from L-lysine.HCl or LLP. Experiment 2 was conducted using a lysine-deficient basal diet containing corn, peanut meal, and feather meal, and all diets were fed to five groups of five chicks from Day 8 to 21 posthatching. Treatment additions again consisted of 0.1 or 0.2% lysine from L-lysine.HCl or LLP. Weight gain and feed efficiency responded linearly (P < 0.01) to increasing levels of lysine from L-lysine-HCl and LLP, and multiple linear regression analysis of weight gain regressed on supplemental lysine intake indicated no difference (P > 0.05) in the response to lysine from L-lysine.HCl or LLP. These data indicate that lysine from LLP is fully bioavailable relative to lysine from crystalline L-lysine.HCl, and could therefore be used as a source of lysine in practical poultry diets.

Citric acid does not improve phosphorus utilization in laying hens fed a corn-soybean meal diet.

Data previously obtained from our laboratory have indicated that citric acid was very effective at improving phytate-P utilization in chicks fed a P-deficient corn-soybean meal (SBM) diet. The objective of the current study was to determine if citric acid would have similar effects in a commercial strain of Single Comb White Leghorn laying hens (n = 432) fed a corn-SBM diet containing 0.10% available P (AP). Dietary treatments were a corn-SBM basal diet (0.10% AP, 3.8% Ca, and 17% CP) supplemented with 0, 1, 2, 3, or 4% citric acid and a positive control diet containing 0.45% AP. Each of the six dietary treatments were fed to six replicate groups of 12 hens from 22 to 40 wk of age. No significant differences in performance were observed among treatments during the first 4 wk of the experiment. Hen-day egg production, feed consumption, feed efficiency, and egg yield were subsequently depressed in hens fed 0, 1, 2, 3, or 4% citric acid compared with hens fed 0.45% AP. The results of this study indicate that citric acid does not improve the utilization of dietary P in laying hens fed a corn-SBM diet containing 3.8% Ca.