Immune responses and resistance to Eimeria acervulina of chickens divergently selected for antibody responses to sheep red blood cells

Genetic resilience in chickens against bacterial, viral and protozoal pathogens

The genome contributes to the uniqueness of an individual breed, and enables distinctive characteristics to be passed from one generation to the next. The allelic heterogeneity of a certain breed results in a different response to a pathogen with different genomic expression. Disease resistance in chicken is a polygenic trait that involves different genes that confer resistance against pathogens. Such resistance also involves major histocompatibility (MHC) molecules, immunoglobulins, cytokines, interleukins, T and B cells, and CD4+ and CD8+ T lymphocytes, which are involved in host protection. The MHC is associated with antigen presentation, antibody production, and cytokine stimulation, which highlight its role in disease resistance. The natural resistance-associated macrophage protein 1 (Nramp-1), interferon (IFN), myxovirus-resistance gene, myeloid differentiation primary response 88 (MyD88), receptor-interacting serine/threonine kinase 2 (RIP2), and heterophile cells are involved in disease resistance and susceptibility of chicken. Studies related to disease resistance genetics, epigenetics, and quantitative trait loci would enable the identification of resistance markers and the development of disease resistance breeds. Microbial infections are responsible for significant outbreaks and have blighted the poultry industry. Breeding disease-resistant chicken strains may be helpful in tackling pathogens and increasing the current understanding on host genetics in the fight against communicable diseases. Advanced technologies, such as the CRISPR/Cas9 system, whole genome sequencing, RNA sequencing, and high-density single nucleotide polymorphism (SNP) genotyping, aid the development of resistant breeds, which would significantly decrease the use of antibiotics and vaccination in poultry. In this review, we aimed to reveal the recent genetic basis of infection and genomic modification that increase resistance against different pathogens in chickens.

Effects of methylsulfonylmethane and neutralizing anti-IL-10 antibody supplementation during a mild Eimeria challenge infection in broiler chickens

A 28-day experiment was conducted in broilers to study the effects of feeding methylsulfonylmethane (MSM) and IL-10-neutralizing antibody from dried egg product (DEP) on the growth performance, immune responsivity, oxidative stress parameters, and gut health outcomes during a mild infection with mixed species of Eimeria. A total of 500 male Ross 308 chicks were allocated to five treatments: sham-inoculated (uninfected) chickens fed control diet (UCON), Eimeria-infected chickens fed control diet (ICON), and Eimeria-infected chickens fed control diet supplemented with 287 U/tonne of DEP (I-DEP), 0.4% MSM, or their combination (I-DEP-MSM), with 10 replicate cages of 10 birds per treatment. All infected groups received 1 mL of an oral inoculum containing Eimeria acervulina (10,000 oocysts), Eimeria maxima (5,000 oocysts), and Eimeria tenella (5,000 oocysts) on study days 7 and 14. Data were analyzed as a two-way ANOVA for all treatments including Eimeria-infected groups, in addition to a single degree of freedom contrast to compare uninfected and infected groups receiving the control diet. Mild Eimeria infection did not influence the growth performance in ICON compared with UCON at any time points. Overall (day 0-28) growth performance parameters were not influenced by either infection or dietary supplementation of MSM or DEP. However, birds in I-DEP-MSM showed improved ADG during study day 7 to 14 (i.e., 7 d after primary inoculation) indicating a beneficial effect immediately after Eimeria infection. Although MSM supplementation reduced thiobarbituric acid reactive substances (day 21 and 28), both MSM and DEP improved the total antioxidant capacity (day 21) in the plasma of infected birds. Histopathological outcomes were not influenced by treatments, and fecal oocyst output was higher in MSM- and DEP-supplemented groups than with ICON, indicating no beneficial effects. Similarly, expression of cecal inflammatory cytokines (IL-10, IL-1β, and interferon-γ) was not affected by MSM, DEP, or their combination. Overall, the current results suggest that both MSM and DEP supplementation may benefit birds during a mild Eimeria infection as indicated by improvements in ADG and oxidative stress outcomes.

Development of a Coccidiosis Disease Challenge Model Using a Commercially Available Live Oocyst Vaccine

With growing cross-disciplinary collaboration among researchers, it is increasingly important to record detailed methodology to prevent the repetition of preliminary experiments. The purpose of this paper is to explain the development of a coccidiosis challenge model for the investigation of dietary interventions to coccidiosis in broiler chickens. The objectives are to select a dose of mixed species coccidial vaccine and evaluate the suitability (ability to produce a consistent, marked change) of selected response variables important to nutritional studies at different times postinfection (PI). Coccivac-B and Coccivac-B52 (Merck Animal Health) were evaluated as the source of coccidia in three trials. Trials 1 and 2 were randomized complete block designs with four doses (0, 10, 20, or 30 times (×) label dose) of Coccivac-B administered to 12 replicate cages of six birds by repeater pipette (Trial 1) or gavaging needle (Trial 2). Trial 3 used a completely randomized design with 0× or 30× label dose of Coccivac-B52 administered by gavaging needle to six replicate cages of six birds. Birds were gavaged at 15 days of age, and response criteria were evaluated 7 days PI in all trials and again at 10 days PI in Trials 1 and 2. All means are reported in order of increasing coccidia dose with significance accepted at P ≤ 0.05. Broiler performance was not affected by coccidia in Trials 1 or 3 but grew poorer with increasing dose from 0 to 7 days PI in Trial 2 (body weight gain, 465, 421, 388, 365 g; feed to gain, 1.37, 1.47, 1.52, 1.58). As coccidia dose increased, nitrogen corrected apparent metabolizable energy decreased (Trial 1, 3387, 3318, 3267, 3170 kcal kg^-1; Trial 2, 3358, 2535, 2422, 2309 kcal kg^-1; Trial 3, not measured), while relative weight, length, and content for intestinal sections increased (Trials 1through 3). Gross lesion (duodenum, jejunum/ileum, ceca) and oocyst count scores (jejunum/ileum, ceca) increased with dose; however, gross scoring often suggested infection in unchallenged birds, a finding unsupported by oocyst count scores. At 7 days PI there was no correlation between midgut gross lesion score and midgut oocyst count score (r = 0.06, P = 0.705), but cecal scores were weakly correlated (r = 0.55, P < 0.001). Administering coccidia via repeater pipette (Trial 1) resulted in respiratory distress in some birds, while use of the gavaging needle (Trials 2 and 3) successfully induced intestinal damage in chickens without resulting in coccidia related mortality. Thirty times the label dose at 7 days PI resulted in the greatest number of response variables that produced a consistent, marked change. Therefore, consideration should be given to these conditions when designing future coccidiosis challenge models using vaccines as a source of coccidia.

Dietary supplementation with anti-IL-10 antibody during a severe Eimeria challenge in broiler chickens

Attenuation of host IL-10 activity during Eimeria infection may elicit a robust Th1 response to eliminate the parasite from the gut epithelium. An experiment was conducted to study the effects of feeding IL-10 neutralizing antibody delivered via a dried egg product (DEP) on growth performance, immune responsivity, and gut health outcomes during a severe challenge with either Eimeria acervulina (study 1) or Eimeria tenella (study 2) following FDA CVM #217 protocol to test anticoccidial products. A total of 720 male Ross 308 chicks were used in each study, with 15 replicate cages of 12 birds and the following 4 treatments: sham-inoculated (uninfected) control diet (UCON), Eimeria-infected control diet (ICON), and Eimeria-infected control diet supplemented with DEP at 2 levels (165 [I-165] or 287 [I-287] U/tonne in study 1 and 143 [I-143] or 287 [I-287] U/tonne in study 2). Individual birds assigned to infected treatment groups received a single oral dose of either 200,000 E. acervulina (study 1) or 80,000 E. tenella (study 2) oocysts at 12 d of age (i.e., d post inoculation [DPI] 0), whereas uninfected birds were sham-inoculated with tap water. A one-way ANOVA was performed on outcomes including growth performance, hematology, serum chemistry profiles, immunophenotyping profiles, and intestinal lesion scores. In both studies, DPI 0 to 7 weight gain, feed intake, and feed conversion ratio were worse (P < 0.05) in all infected groups compared with the UCON group. Compared with ICON, DEP supplementation elicited no differences on overall growth performance. Histopathology and lesion scores revealed severe damage to the gut epithelium owing to the Eimeria challenge, yet DEP supplementation did not improve these outcomes or oocyst shedding, hematological measurements, or serum chemistry. However, DEP supplementation improved (P < 0.05) the percentage of circulating CD3⁺ cells at 6 DPI in study 2. These results indicate that DEP does not appear to elicit a coccidiostatic effect during a severe infection with E. acervulina or E. tenella.

Breeding for high specific immune reactivity affects sensitivity to the environment

Lipopolysaccharides (LPS) are present in high levels in the air of chicken houses and likely have immune-modulating effects. In this study, layers from the 30th generation of a divergent selection experiment for humoral immune reactivity to subcutaneously administered sheep red blood cells were concurrently intratracheally challenged with human serum albumin (HuSA) and LPS at 7 and 12 wk of age following a crossing over design. Chickens selected for high humoral immune reactivity (H line) showed higher specific antibody responses to intratracheally administered HuSA and a higher level of natural antibody binding keyhole limpet hemocyanin compared with chickens genetically selected for low humoral immune reactivity (L line), and were also more sensitive to immune modulation by LPS at 7 wk of age. Body weight gain was negatively affected by LPS at 7 wk of age in the L line, but after 12 wk of age in the H line. Egg production was lower and delayed in the H line. We conclude that these chicken selection lines differ in sensitivity to the environment (LPS), and consequently may therefore also react differently to infection, vaccinations, and other immune responses. In addition, selection for immune responsiveness affected growth and egg lay.

Immune-related gene expression in two B-complex disparate genetically inbred Fayoumi chicken lines following Eimeria maxima infection

To investigate the influence of genetic differences in the MHC on susceptibility to avian coccidiosis, M5.1 and M15.2 B-haplotype-disparate Fayoumi chickens were orally infected with live Eimeria maxima oocysts, and BW gain, fecal oocyst production, and expression of 14 immune-related genes were determined as parameters of protective immunity. Weight loss was reduced and fecal parasite numbers were lower in birds of the M5.1 line compared with M15.2 line birds. Intestinal intraepithelial lymphocytes from M5.1 chickens expressed greater levels of transcripts encoding interferon-gamma (IFN-gamma), interleukin-1beta (IL-1beta), IL-6, IL-8, IL-12, IL-15, IL-17A, inducible nitric oxide synthase, and lipopolysaccharide-induced tumor necrosis factor-alpha factor and lower levels of mRNA for IFN-alpha, IL-10, IL-17D, NK-lysin, and tumor necrosis factor superfamily 15 compared with the M15.2 line. In the spleen, E. maxima infection was associated with greater expression levels of IFN-gamma, IL-15, and IL-8 and lower levels of IL-6, IL-17D, and IL-12 in M5.1 vs. M15.2 birds. These results suggest that genetic determinants within the chicken MHC influence resistance to E. maxima infection by controlling the local and systemic expression of immune-related cytokine and chemokine genes.

Eimeria tenella: B-cell epitope mapping following primary and secondary infections

Immunisation against coccidiosis has become more reliable and effective with improved administration techniques for new vaccines. On the other hand, an ideal coccidial vaccine should contain both B- and T-cell immunogenic epitopes. Fine specificity of B-cell epitopes recognised by antibodies prepared following primary and secondary infections with Eimeria tenella were studied using "PepScan" techniques. Mapping of B-cell epitopes within an antigenic sequence from E. tenella showed that four distinct types of epitopes were recognised by the host immune system during the primary and secondary infections with the parasite. These observations demonstrated that new epitopes are also involved in induction of antibody responses following the secondary infection.

Coccidial infections in housed lambs: oocyst excretion, antibody levels and genetic influences on the infection

Faecal Eimeria oocyst excretion, body weights, humoral antibodies against E. ovinoidalis sporozoite antigen and related heritabilities were determined in housed Merinoland sheep lambs throughout a period of 100 days after birth in Germany. Altogether 10-11 Eimeria spp. were found. Cumulative incidences of E. ovinoidalis and E. weybridgensis/crandallis increased rapidly resulting in almost 100% incidence in 8 weeks old lambs. In the other species, the cumulative incidence increased more continuously. Except for E. granulosa oocysts of all species had been excreted at last once until day 30. By far the highest oocyst counts (OpG) were observed with E. ovinoidalis, followed by E. weybridgensis/crandallis. High counts were limited to the period of 5-8 weeks after birth. In the other Eimeria species oocyst counts persisted at comparatively low levels until the end of the observation period although their proportion of the total counts increased with age of the lambs. Time courses of oocyst excretion suggest an early onset of effective immunity to the major Eimeria spp., which differed for the minor species. Mean and maximum oocyst counts and body weights of the lambs were inversely correlated suggesting negative effects of the infection on the lamb's performance. High mean antibody levels on day 7 after birth dropped until day 40 and increased subsequently again. There were no indications that maternal antibodies were protective. Antibody levels on day 40 after birth were positively correlated with oocyst counts in the faeces whereas those determined on day 80 were independent of infection parameters. Heritabilities of log(10)OpG were not significantly different from 0 up to an age of 60 days. Later estimated values were between 0.54 and 0.79 suggesting that immune protective effects rather than innate effects determining disease susceptibility are under genetic influence.

A hemolysis-hemagglutination assay for characterizing constitutive innate humoral immunity in wild and domestic birds

Methods to assess immunocompetence requiring only a single sample are useful in comparative studies where practical considerations prevent holding or recapturing individuals. The assay for natural antibody-mediated complement activation and red blood cell agglutination described here, requiring approximately 100 microl of blood, is highly repeatable. The effects of complement deactivation, 2-mercaptoethanol (2-ME), age, and lipopolysaccharide (LPS)-induced sickness response were examined to validate comparisons among diverse avian species. Complement deactivation by heating significantly reduces lysis and treatment with 2-ME reduces both lysis and agglutination. Lysis and agglutination both increase with age in chickens; LPS treatment does not influence these variables in 11-week-old chickens. In a comparison of 11 species, both lysis (0.0-5.3 titers) and agglutination (1.8-8.0 titers) vary significantly among species. Accordingly, this assay can be used to compare constitutive innate humoral immunity among species and with respect to age, sex, and experimental treatments within populations.

Quantitative trait loci for body weight in layers differ from quantitative trait loci specific for antibody responses to sheep red blood cells

Quantitative trait loci for BW at 4, 6, 8, 12, and 18 wk of age were detected in an experimental F2 cross of layers divergently selected for primary antibody response to SRBC. A negative phenotypic correlation between levels of antibody titers and BW, was reported earlier within founder lines. The entire experimental population was genotyped with 174 microsatellite markers equally distributed over the genome. Two genetic models were applied in the QTL analysis: a half-sib model and a line-cross model, both using the regression interval method. In the half-sib model, 3 QTL for BW at 4 wk of age on chromosomes GGA2, GGA3, and GGA9 were detected. For BW at 6 wk of age, 3 QTL were detected on GGA2, GGA3, and GGA6. For BW at 8 wk of age, a QTL was detected on GGA7, and for BW at 12 and 18 wk of age, a QTL was detected on GGAZ. With the line-cross analysis model, one QTL on GGA7 for BW at 4 wk of age was detected. Two QTL were detected on GGA3 and GGA7 for BW at 6 wk of age, and one on GGA3 was detected for BW for 8 and 12 wk of age. For BW at 18 wk of age, there were no QTL under the line-cross analysis model. The present data suggest that 1) a different set of genes affects the early and the late growth, and 2) genes selected to humoral immune responsiveness are different from genes underlying growth.

Differential Effects of Lipopolysaccharide and Lipoteichoic Acid on the Primary Antibody Response to Keyhole Limpet Hemocyanin of Chickens Selected for High or Low Antibody Responses to Sheep Red Blood Cells

Various bacterial components are potent activators of the innate immune system and probably (in)directly determine subsequent specific immune responses. Therefore, effects of i.v. administered Salmonella enteriditis-derived lipopolysaccharide (LPS) and Staphylococcus aureus-derived lipoteichoic acid (LTA), respectively, on the primary antibody (Ab) response to keyhole limpet hemocyanin (KLH) were studied in cocks from 2 lines divergently selected for high (H line) and low (L line) Ab responses to SRBC. The Ab responses to KLH were significantly affected by a line-by-treatment-by-time interaction. Significantly higher Ab titers to KLH, S. aureus LTA, and S. enteriditis LPS were found in H line birds than in the L line birds. Ab titers to KLH were enhanced if the chickens were intravenously pretreated 24 h earlier with LTA but decreased if the chickens were intravenously pretreated 24 h earlier with LPS. Ab responses to S. enteriditis LPS were significantly enhanced when birds were immunized with KLH or pretreated with S. aureus LTA. Ab responses to S. aureus LTA were also significantly enhanced when birds were immunized with KLH or pretreated with LTA and subsequently immunized with KLH. Our findings suggest that LTA and LPS have immunomodulatory features in chickens, albeit in opposite directions. In addition, KLH acted in an immunomodulatory role too. Possible mechanisms underlying our observations and the role of LTA and LPS in polarization of the specific immune response in chickens are discussed.

Serum haemolytic complement activities in 11 different MHC (B) typed chicken lines

To study the relation between serum complement levels and the chicken MHC (B) complex, complement haemolytic activity was measured in sera from hens from seven pure-bred B-typed White and one Brown Leghorn lines, and three ISA-Warren lines that had been divergently selected for antibody responses to sheep red blood cells (SRBC). Significant differences occurred in the serum haemolytic complement activities, both belonging to the classic (CPW) and the alternative (APW) pathways, among the 11 different haplotyped chicken lines. Hens with high CPW and high APW titres predominantly displayed the B2 or B21 haplotypes. Chickens with low CPW and APW were found in B14 and B15 haplotypes. Haplotype B14 appears to be different in complement levels when present into the pure-bred lines or into the ISA-Warren line selected for low antibody responses to SRBC. Otherwise, the presence of B21 in ISA-Warren line selected for high antibody responses to SRBC does not differ with the B21 in the inbred lines (except in the NL-line for CPW values). In general the haplotypes B2 and B21 are found in chicken lines with enhanced disease resistance, and the B15 haplotype has been connected with enhanced disease susceptibility. Our results suggest that levels of haemolytic complement activity, either from the classical or from the alternative pathways, may underlie part of the immunocompetence ascribed to the MHC (B) complex in chickens.

Detection of different quantitative trait loci for antibody responses to keyhole lympet hemocyanin and Mycobacterium butyricum in two unrelated populations of laying hens

Quantitative trait loci involved in the primary antibody response to keyhole lympet hemocyanin (KLH) and Mycobacterium butyricum were detected in two independent populations of laying hens. The first population was an F2 cross (H/L) of lines divergently selected for either high or low primary antibody responses to SRBC, and the second population was an F2 cross between 2 commercial layer lines displaying differences in feather pecking behavior (FP). Both populations were typed with microsatellite markers widely distributed over the genome with similar intervals between markers. Titers of antibodies binding KLH and M. butyricum were measured for all individuals by ELISA. Two genetic models were applied to detect QTL involved in the humoral immune response: a half-sib model and a line-cross model, both using the regression interval method. In the half-sib analysis, 2 QTL (on GGA14 and GGA27) were detected for the antibody response to KLH for the H/L population, and 2 QTL (on GGA14 and GGA18) were detected for the FP population. Only 1 QTL was detected for M. butyricum on GGA14 in the FP population using the half-sib analysis model. Two QTL were detected for the FP population on GGA2 and GGA3 using the line-cross analysis model. A QTL for the primary antibody response to KLH detected on GGA14 was validated in both populations under the half-sib analysis model. The present data suggest differences in the genetic regulation of antibody responses to two different T-cell dependent antigens.

Detection of QTL for immune response to sheep red blood cells in laying hens

The aim of this study is to detect quantitative trait loci (QTL) involved in the regulation of the primary and the secondary immune response to sheep red blood cells (SRBC) in a resource population using microsatellite DNA markers. The F2 resource population originates from a cross of two divergently selected lines for either high (H line) or low (L line) primary antibody response to SRBC. The F2 population consisted of six half-sib families, three families per each of reciprocal crosses. Total antibody titres to SRBC were determined by agglutination in serum from all birds. F2, F1 and F0 generations were genotyped for 170 microsatellite markers, using a whole-genome scan approach. The half-sib and the line-cross analyses were performed to determine QTL regions associated with regulation of the immune response. In the half-sib analysis, four QTL for SRBC primary response have been identified: on GGA3, GGA5, GGA16 and GGA23. No QTL was identified for SRBC secondary response under the half-sib model. In the line-cross analysis, three QTL were identified on GGA10, GGA16 and GGA27 for SRBC primary response and five QTL were identified on GGA6, GGA9, GGA15, GGA16 and GGA27 for SRBC secondary response. Subsequently, the family contribution of individual families to the QTL was analysed. The family with the largest contribution was genotyped with additional microsatellite markers in the QTL region on GGA5. The extended half-sib analysis with additional genotype information results in narrowing down the QTL region on GGA5.

Reproductive effort reduces long-term immune function in breeding tree swallows (Tachycineta bicolor)

We examined whether strategies of reproductive allocation may reduce long-term immunocompetence through the effects of manipulated effort on secondary or acquired immunity. We tested whether increased reproductive effort leads to reduced immune function and survival by manipulating brood size in tree swallows (Tachycineta bicolor) and exposing breeding females to a primary and secondary exposure of sheep red blood cells to elicit a humoral immune response. Females raising enlarged broods produced fewer secondary antibodies than did females raising control or reduced broods. Most importantly, individuals with high secondary responses were more likely to survive to breed 3 years after brood manipulations, suggesting that differences in disease susceptibility may be caused by trade-offs in reproductive allocation. We also found that individual quality, measured by clutch initiation date, mediated the effects of brood manipulations, with higher-quality birds showing a greater ability to deal with increases in effort.

Protective effects of sugar cane extracts (SCE) on Eimeria tenella infection in chickens

The effects of oral administration of sugar cane extracts (SCE) on Eimeria tenella oocysts infection in chickens were studied with 2 different experiments. In Experiment 1, 3-week-old inbred chickens (MHC; H.B15) were inoculated into the crop with SCE (500 mg/kg/day) for 1 day or 3 consecutive days, and then challenged with E. tenella sporulated oocysts (2 x 10(4) cells/chicken). In Experiment 2, 1-week-old chickens were orally administered SCE at the same dose for 3 consecutive days, and then initially infected with E. tenella sporulated oocysts (2 x 10(3) cells/chicken). At 2 and 3 weeks of age, these chickens were immunized intravenously with the mixed antigens of sheep red blood cells (SRBC) and Brucella abortus (BA). At 4 weeks of age, chickens were challenged with E. tenella sporulated oocysts (1 x 10(5)/chicken). Challenged chickens with E. tenella oocysts showed markedly decreased body weight gain/day, severe hemorrhage and great number of shedding oocysts in feces and high lesion scores. Oral administration of SCE and initial infection with oocysts (2 x 10 (3)/chicken) resulted in a remarkable improvement in body weight gain/day, hemorrhage, the number of shedding oocysts and lesion score, compare to other infected groups. In addition, SCE-inoculated chickens with the initial infection showed a significant increase in antibody responses against SRBC and BA and also improvement in decreased relative proportions of Bu-1a(+) and CD4( )cells in cecal tonsil lymphocytes of E. tenella-challenged chickens. Cecal tissues of chickens administered SCE and initially infected with E. tenella oocysts showed lower numbers of schizonts, gametocytes and oocysts than those of infected control chickens. These results suggest that SCE have immunostimulating and protective effects against E. tenella infection in chickens.

Associations of six candidate genes with antibody response kinetics in hens

The chicken B-cell marker (ChB6), caspase-1, inhibitor of apoptosis protein-1 (IAP-1), interleukin-15 receptor alpha-chain (IL-15Ralpha), interleukin-2 receptor gamma-chain (IL-2Rgamma), and immunoglobulin supfamily gene (ZOV3), as physiological candidate genes for chicken immune response, were selected to investigate associations with antibody kinetics to SRBC and killed B. abortus. An F2 population was derived from mating highly inbred (>99%) males of two MHC-congenic Fayoumi lines (named M5.1 and M15.2) with G-B1 Leghorn hens. Antibody response to SRBC and B. abortus after immunization at 19 and 22 wk were measured. Secondary phase parameters of maximum titers (Ymax) and time required to achieve Ymax (Tmax) were estimated from postsecondary titers by using a nonlinear regression model. The DNA polymorphisms of six genes were identified, and associations of single nucleotide polymorphisms (SNP) in the six genes with antibody response parameters were analyzed. Significant main effects of the gene polymorphisms were mostly found in the lineage of the M5.1 grandsire and primarily on antibody response to B. abortus. There was general agreement of allelic effect within antibody parameters among genes. These results suggest that the SNP characterized in the study may serve as markers for genetic enhancement of humoral immune capacity in the chicken.