The impact of β-glucans on performance and response of broiler chickens during a coccidiosis challenge

Coccidiosis is a costly parasitic disease to the poultry industry with multiple prevention methods being explored to control its impact. This study evaluated the feeding effects of β-glucans on performance and responses of chickens during a coccidiosis challenge. Cobb 500 male broilers (n = 1280) were assigned to 1 of 8 treatment groups (8 replicate pens; 20 birds/pen) in a 2 × 4 factorial arrangement, including non-infected and Eimeria-infected birds fed for 28 d a control diet, control + BG (150 g/MT Algamune 50), control + BGZn (100 g/MT Algamune 50 Zn), and control + 0.01% Salinomycin (Sal). On d15, birds in the challenge groups received a mixed Eimeria inoculum. Birds and feed were weighed weekly on a per pen basis to evaluate body weight gain (BWG), feed intake (FI), and feed conversion ratios (FCR). Lesion scores were assessed 6 d post infection (d21) on 3 birds per pen. Performance data were subjected to ANOVA and differences were established using the LS-MEANS statement with significance reported at P ≤ 0.05. There were minor differences in lesion scores among the dietary treatments in the infected groups with reduced duodenal and cecal scores in the Sal group compared to the BGZn and BG groups, respectively. The coccidiosis challenge main effect resulted in a significant reduction in 0-28 d BW and FI. Dietary treatment resulted in non-significant effect on BWG, but Sal addition resulted in increased FI. A significant diet X challenge interaction resulted in higher FCR in the Eimeria-challenged birds supplemented with Sal and BGZn in comparison to the other challenged groups, likely due to reduced mortality in the challenged Sal and BGZn groups. Body composition analysis at d28 revealed that the Eimeria challenge reduced both fat and lean tissue contents, where the β-glucans and Sal birds had lower fat percent than control birds.

Satellite cell-mediated breast muscle regeneration decreases with broiler size

Satellite cells (SCs) reside between the sarcolemma and basal lamina of muscle fibers and are the primary contributor of DNA for post-hatch muscle growth and repair. Alterations in SC content or properties by intrinsic and extrinsic factors can have detrimental effects on muscle health and function, and ultimately meat quality. We hypothesized that disrupted SC homeostasis may account in part for the increased breast myopathies observed in growing broilers. To test this hypothesis, we selected broilers with different body weights at comparable ages and studied SC characteristics in vitro and in vivo. Data shows that SC numbers in the breast muscles decrease (P < 0.001) and their inherent abilities to proliferate and differentiate diminish (P < 0.001) with age and size. Further, when breast muscle is presented with an insult, muscle of larger broilers regenerates more slowly than their smaller, age-matched counterparts arguing that SC quality changes with size and age. Together, our studies show that birds with greater muscle hypertrophy have less SCs with diminished ability to function, and suggest that aggressive selection for breast growth in broilers may exhaust SC pools when birds are grown to heavier processing weights. These findings provide new insights into a possible mechanism leading to breast myopathies in the poultry industry and provide targets for mitigating adverse fresh breast quality.

Immunomodulatory role of probiotics in poultry and potential in ovo application

Recently, there has been an increasing debate regarding the use of sub-therapeutic antibiotics in animal feed. This stems from worries that this practice may result in microbial resistance to human antibiotics employed in treating infections, thus causing a human health concern. Due to this tension, the poultry industry is under mounting pressure to reduce the use of these agents as feed additives and alternative control methods have taken the forefront in the research community. Investigators are searching for the latest alternative that will protect flocks from disease, while not hindering performance or negatively impacting profit margins. Probiotic supplementation is one option currently being explored as a means of improving performance and reducing the amount and severity of enteric diseases in poultry, and subsequent contamination of poultry products for human consumption. Probiotics are live, nonpathogenic microorganisms known to have a positive effect on the host by beneficially modifying gut microbiota and modulating the immune system. This review will discuss the role of probiotics in poultry, including their effects on performance, immune response and host defence against disease. Also addressed will be the recent applications of supplementing probiotics in ovo as an innovative means to administer such additives to promote early colonisation of beneficial bacteria.

Changes in expression of an antimicrobial peptide, digestive enzymes, and nutrient transporters in the intestine of E. praecox-infected chickens

Coccidiosis is a major intestinal disease of poultry, caused by several species of the protozoan Eimeria. The objective of this study was to examine changes in expression of digestive enzymes, nutrient transporters, and an antimicrobial peptide following an Eimeria praecox challenge of chickens at days 3 and 6 post-infection. Gene expression was determined by real-time PCR and analyzed by one-way ANOVA. In the duodenum, the primary site of E. praecox infection, a number of genes were downregulated at both d3 and d6 post-infection. These genes included liver expressed antimicrobial peptide 2 (LEAP2), the cationic (CAT1), anionic (EAAT3), and L-type (LAT1) amino acid transporters, the peptide transporter PepT1 and the zinc transporter ZnT1. Other transporters were downregulated either at d3 or d6. At both d3 and d6, there was downregulation of B(o)AT and CAT1 in the jejunum and downregulation of LEAP2 and LAT1 in the ileum. LEAP2, EAAT3, and ZnT1 have been found to be downregulated following challenge with other Eimeria species, suggesting a common cellular response to Eimeria.

Supplementing antioxidants to pigs fed diets high in oxidants: I. Effects on growth performance, liver function, and oxidative status

The objective of the study was to determine the effects of a dietary antioxidant blend (ethoxyquin and propyl gallate) and vitamin E on growth performance, liver function, and oxidative status in pigs fed diets high in oxidants. Crossbred barrows (n=100, 10.91±0.65 kg BW, 36±2 d of age, Landrace×Duroc) were allotted to 5 treatments on the basis of BW (5 replicate pens per treatment, 4 pigs per pen). Treatments included 1) HO, high-oxidant diet containing 5% oxidized soybean oil and 10% PUFA source (providing 2.05% docosahexaenoic acid in the diet), 2) VE, the HO diet with 11 IU/kg of added vitamin E, 3) AOX, the HO diet with antioxidant blend (135 mg/kg), 4) VE+AOX, the HO diet with both vitamin E and antioxidant blend, and 5) SC, a standard corn-soy control diet. The trial lasted for 118 d; on d 83, the HO diet pigs were switched to the SC diet because the animals were displaying very poor health. Compared with SC pigs, HO pigs had decreased ADG (0.92 vs. 0.51 kg for d 26 to 55, 1.29 vs. 0.34 kg for d 56 to 82; P<0.05) and ADFI (1.84 vs. 0.96 kg for d 26 to 55, 3.41 vs. 1.14 kg for d 56 to 82; P<0.05). However, switching the HO pigs to the SC diet resulted in HO pigs having a greater ADG than VE-fed pigs from d 83 to 118 (0.90 vs. 0.60 kg; P<0.05). The antioxidant blend restored pig performance to a level similar that of pigs fed the SC diet (P>0.05) with greater G:F for the entire period (0.44 vs. 0.38; P<0.05). A greater liver to BW ratio was found in HO compared with other treatments on d 55 and in VE on d 118. Total bilirubin concentration in plasma of HO pigs on d 55 was greater than that in VE+AOX pigs (P<0.05), whereas on d 118, bilirubin concentration in VE was higher than those in VE+AOX and SC (P<0.05). A similar trend was observed in aspartate transaminase. Plasma concentrations of thiobarbituric acid reactive substances (TBARS) and carbonyl were elevated (P<0.05) in the HO pigs compared with the SC pigs on d 55 but not on d 118. Liver TBARS and carbonyl concentrations showed a similar trend, except that HO pigs had the greatest carbonyl concentration on d 118. Pigs fed AOX diets had plasma and liver TBARS and carbonyl concentrations similar to those fed SC diets. In the oxidative stress model used in this study, dietary addition of antioxidant blend or antioxidant blend+vitaimin E was effective in improving growth, liver function, and plasma markers of oxidative stress, but VE alone was not.

Effects of a dietary antioxidant blend and vitamin E on fatty acid profile, liver function, and inflammatory response in broiler chickens fed a diet high in oxidants

The aim of the current study was to determine the effects of a dietary antioxidant blend and vitamin E on fatty acid profile, inflammatory response, and liver function. Cobb 500 male broilers (n = 1,200, d 0) were randomly distributed into 6 treatments with 10 replicate floor pens. Treatments included (1) a high-oxidant diet, with vitamin E at 10 IU/kg, 3% oxidized oil, 3% polyunsaturated fatty acids (PUFA) source (HO); (2) the HO diet with vitamin E at 200 IU/kg (VE); (3) the HO diet with an antioxidant blend at 135 mg/kg (AOX); (4) the HO diet with both vitamin E at 200 IU/kg and an antioxidant blend at 135 mg/kg (VE+AOX); (5) standard control (SC); and (6) a positive control, which was the SC diet with an antioxidant blend at 135 mg/kg. The concentrations of 20:4, 20:5, 22:5, 22:6, and all the n-3 fatty acids were greater in the abdominal fat of HO, VE, AOX, and VE+AOX birds than SC and positive control birds on d 21 and 42 (P < 0.001). Compared with HO treatment, AOX and VE+AOX preserved the deposition of PUFA better (P < 0.001). The HO birds had greater concentrations of aspartate aminotransferase on d 21 and 42, and γ-glutamyl transferase on d 21, whereas AOX and VE+AOX chickens had restored γ-glutamyl transferase concentration (P < 0.01). The inflammation scores of abdominal fat of AOX and VE+AOX birds were lower than the HO on d 21 (P < 0.001). Compared with SC, the VE and VE+AOX birds exhibited greater vacuole scores on d 21 and 42 (P < 0.01). The lower vacuoles score in SC was associated with a greater expression of peroxisome proliferator activated receptor -γ and -α (P < 0.05). The expression of inflammatory genes in the liver did not differ among treatments. In conclusion, the AOX and AOX+VE diets were effective in preserving PUFA in the abdominal fat, moderately improved liver function, and reduced inflammation in fat.

Effects of a dietary antioxidant blend and vitamin E on growth performance, oxidative status, and meat quality in broiler chickens fed a diet high in oxidants

The aim of the study was to determine the effects of a dietary antioxidant blend (AB) and vitamin E on performance, oxidative status, and meat quality. Cobb 500 male broilers (n = 1,200, d 0) were randomly distributed into 6 treatments with 10 replicate pens. Treatments included 1) HO: high oxidant diet, vitamin E at 10 IU/kg, 3% oxidized soybean oil, 3% polyunsaturated fatty acid (PUFA) source; 2) VE: the HO diet with vitamin E at 200 IU/kg; 3) AOX: the HO diet with AB at 135 mg/kg; 4) VE+AOX: the HO diet with vitamin E at 200 IU/kg and AB at 135 mg/kg; 5) SC: standard control; and 6) PC: positive control, the SC diet with AB at 135 mg/kg. From d 0 through d 21, high oxidant diet treatment birds had greater BW, ADG, and ADFI than the SC birds; the AOX birds had better G:F on d 10 and 42, and from d 0 to 42 than SC birds (P < 0.05). The plasma TBA reactive substance level was lower in the AOX birds than the VE treatment birds in all phases (P < 0.05). High oxidant diet treatment birds had greater α-1-acid glycoprotein levels on d 10 than SC and PC birds (P < 0.05). The AOX, PC, and SC birds had a greater level of uric acid than the HO and VE+AOX birds on d 10. Superoxide dismutase expression in the liver was less with the HO treatment compared with the SC treatment on d 7 (P < 0.05). The vitamin E concentration in the breast muscle was greatest in the VE birds, whereas vitamin A concentration was greater in the PC birds compared with the SC birds on d 21 (P < 0.05). Compared with VE and AOX, the HO treatment had greater drip loss (P < 0.05). In conclusion, dietary addition of AOX was effective in improving growth, moderately restored the whole body antioxidant capability, and reduced drip loss.

Immune responses to dietary beta-glucan in broiler chicks during an Eimeria challenge

Escalating consumer concerns regarding pathogen resistance have placed the poultry industry under mounting pressure to eliminate the use of chemotherapeutic agents as feed additives. One possible alternative receiving increased attention is the use of immunomodulators such as β-glucan. A study was conducted to investigate the effects of a yeast-derived β-glucan (Auxoferm YGT) on broiler chick performance, lesion scores, and immune-related gene expression during a mixed Eimeria infection. Day-old chicks were fed diets containing 0, 0.02, or 0.1% YGT. On d 8 posthatch, one-half of the replicate pens were challenged with a mixed inoculum of Eimeria acervulina, Eimeria maxima, and Eimeria tenella. Measurements were taken and samples collected on d 4, 10, 14, and 21 posthatch. Dietary supplementation had no effect on performance or mortality. On d 14, 3 birds per pen (n = 24/treatment) were scored for intestinal coccidia lesions. Gross lesion severity was significantly reduced in birds supplemented with 0.1% YGT. On d 10, inducible nitric oxide synthase (iNOS) expression was downregulated in the jejunum of challenged birds fed 0.1% YGT. Expression of iNOS in the ileum was downregulated in the nonchallenged birds, but upregulated in the challenged birds fed 0.1% YGT on d 14. Interleukin (IL)-18 was upregulated in the jejunum of 0.1% YGT-treated birds. Interferon (IFN)-γ expression was decreased in challenged and nonchallenged birds fed 0.1% YGT. The IL-4 expression was downregulated in the nonchallenged birds with 0.1% YGT diet supplementation. The IL-13 and mucin-1 levels were also reduced due to β-glucan supplementation. Mucin-2 expression was increased in the nonchallenged birds, but decreased in the infected birds fed 0.1% YGT. These results suggest that although Auxoferm YGT at doses of 0.02 and 0.1% does not influence performance, it significantly reduces lesion severity and is capable of altering immune-related gene expression profiles, favoring an enhanced T helper type-1 cell response during coccidiosis.

Performance and immune responses to dietary beta-glucan in broiler chicks

During the first week posthatch, the avian immune system is immature and inefficient at protecting chicks from invading pathogens. Among immunomodulators, beta-glucans are known as biological response modifiers due to their ability to activate the immune system. Current research suggests that beta-glucans may enhance avian immunity; however, very little is known about their influence on regulation of immune function. A study was performed to evaluate the effects of dietary beta-glucan on growth performance, immune organ weights, peripheral blood cell profiles, and immune-related gene expression in the intestine. One-day-old chicks were fed a diet containing 0, 0.02, or 0.1% yeast beta-glucan (n = 30/treatment). On d 7 and 14 posthatch, body and relative immune organ weights were measured and small intestinal sections were collected to evaluate gene expression by quantitative real-time PCR. Peripheral blood samples were also collected to determine heterophil:lymphocyte ratios. Supplementation of beta-glucan did not significantly affect BW gains, and no significant differences were observed among groups for relative immune organ weights or heterophil:lymphocyte ratios. Compared with controls, expression of interleukin (IL)-8 was downregulated in the beta-glucan-treated groups on d 7 and 14. On d 14, beta-glucan inclusion resulted in increased inducible nitric oxide synthase expression. Expression of IL-18 was upregulated on d 7 but reduced on d 14 due to beta-glucan supplementation. On d 7, interferon-gamma and IL-4 expression decreased in the beta-glucan-treated groups. However, on d 14, IL-4 expression was upregulated in the supplemented groups. Intestinal expression of IL-13 was also downregulated in the beta-glucan-treated birds on d 7. These results suggest that dietary inclusion of beta-glucans altered the cytokine-chemokine balance; however, it did not elicit a robust immune response in the absence of a challenge, resulting in no deleterious effects on performance.

Influence of Pediococcus-Based Probiotic on Coccidiosis in Broiler Chickens

Coccidiosis is the major parasitic disease of poultry and is caused by the apicomplexan parasites Eimeria. Drugs and live vaccines are the 2 main control measures of the disease; however, due to increasing concerns with prophylactic drug use and the high cost of vaccines, alternative control methods are needed. Recent evidence that various dietary and live microbial supplements can influence host immunity against enteric diseases prompted us to investigate the role of a Pediococcus-based probiotic on coccidiosis in broiler chickens. In the present study, we examined BW gains, oocyst shedding, and antibody responses of broilers fed the commercial probiotic MitoGrow. Day-old chicks were fed either a regular broiler diet or 1 of 2 probiotic diets supplemented with 0.1% (MG 0.1) or 0.2% MitoGrow. Chicks were orally challenged with 5,000 or 10,000 sporulated oocysts of Eimeria acervulina or with 5,000 Eimeria tenella oocysts on d 10 or 12 of age, respectively. In E. acervulina-infected birds, the MG 0.1 group improved (P < 0.05) weight gain as compared with the other 2 groups and reduced (P < 0.05) oocyst shedding in birds infected with 5,000 E. acervulina oocysts. In E. tenella-infected birds, Eimeria-specific antibody levels were higher (P < 0.05) in the Mito-Grow-fed groups, especially in the MG 0.1 birds, compared with the regular diet group, although their oocyst shedding and weight gains were not clearly improved. These results demonstrate that this Pediococcus acidilactici-based probiotic effectively enhances the resistance of birds and partially protects against the negative growth effects associated with coccidiosis, particularly when supplemented at 0.1% MitoGrow of the diet.

Immunopotentiating effect of a Fomitella fraxinea-derived lectin on chicken immunity and resistance to coccidiosis

This study reports a novel immunopotentiating effect of a lectin (FFrL) extracted from the mushroom Fomitella fraxinea on poultry cell-mediated immunity and poultry coccidiosis. We describe the extraction of FFrL, its in vitro mitogenic activity and in vivo protection against an oral challenge infection with Eimeria acervulina. When tested on several cell types, crude FFrL agglutinated mouse erythrocytes and thymocytes and various other cells including murine and human cell lines. However, crude FFrL did not agglutinate human erythrocytes. Crude FFrL showed a potent mitogenic activity on chicken splenic lymphocytes, and at lower concentrations it exerted stronger mitogenic activity than Concanavalin A, a well-known potent mitogen for lymphocytes. Further, FFrL significantly induced (P < 0.05) nitric oxide secretion in HD11 cells and suppressed (P < 0.05) RP9 tumor cell growth in a dose-dependent fashion. When injected into 18-d-old chicken embryos followed by a posthatch oral E. acervulina challenge infection, FFrL treatment significantly protected chickens against weight loss associated with coccidiosis (P < 0.05). Injecting embryos with FFrL also resulted in significant reduction in oocyst shedding as compared with the control saline-injected birds (P < 0.05). The results of this study demonstrate that FFrL can be an effective growth promoting and immunostimulating agent in poultry during coccidiosis.

Performance of broiler chickens fed diets supplemented with a direct-fed microbial

From hatch to 18 d of age broilers were fed starter diets with (0.9 kg/ton) or without direct fed microbial (DFM). At 18 d, birds were weighed and, within DFM treatment (trt), randomly assigned to battery pens. In Exp 1, a 2 x 2 factorial arrangement of nutrient density [control (C, 19.3% protein (CP), 0.84%, Ca 0.37% nonphytin P (nPP); and 17.1% CP, 0.8% Ca, and 0.3% nPP in the grower (Gr) and finisher (Fn) diets, respectively) and moderate (M) (17% CP, 0.69% Ca, 0.30% nPP; 15% CP, 0.66% Ca, 0.25% nPP in the Gr and Fn diets, respectively)] and DFM concentration [0 or 0.9 kg/ton (++)] was used. Exp 2 was a 2 (DSM at 0 and 0.45 kg/ton) x 3 (nutrient densities) factorial. Exp 2 included a low (L) nutrient density that differed from diet M only in Ca and nPP concentrations and an added trt, diet M with 0.45 kg/ ton DFM as in Exp 1. At the end of the Gr and Fn weight, feed efficiency, apparent nutrient retention were determined, and 4 birds per pen were sampled for tibia ash. In Exp 2, gains in the Gr phase were 1,122.0, 983.7, 1,121.5, 930.7, and 1,151.5 g in birds fed the C, M, M+, L, and L+ diets, respectively. Addition of DFM to the M diet overcame the negative effect of nutrient concentration on performance but not when the L diet was fed. Nutrient level and DFM affected apparent protein, Ca, and P retention at 32 or 42 d of age with retention increasing as nutrient level decreased and with DFM added to the diet. Ca and P retention at 28 d (Exp 1) was higher in birds fed M++ (45.8 and 46%, respectively) than in those fed the C diet (38.7 and 40.0%, respectively). Feeding the M and L diets resulted in lower tibia ash than that of birds fed the C diet, but the addition of DFM to low nutrient diets overcame this negative effect.

Salmonella enteritidis clearance and immune responses in chickens following Salmonella vaccination and challenge

Our previous work showed that the cell-mediated immunity (CMI) was enhanced by live Salmonella vaccine (LV). The objective of this study was to evaluate the impact of live and killed Salmonella vaccines on Salmonella enteritidis (SE) clearance and to determine if the clearance was mediated by cell-mediated and/or humoral immunity. Chickens were first immunized at 2 weeks of age followed by a booster dose at 4 weeks, challenged with live SE 2 weeks later (6-week-old) and tested for CMI, antibody response and SE clearance 1-week post SE-challenge (7-week-old). Spleen cell proliferation induced by SE-flagella and Concanavalin A (Con A) were significantly higher and SE shedding was significantly lower in the LV group. The splenic CD3 population was significantly lower and B cells were higher in the control group compared to all the SE-challenged groups (with and without vaccination). Serum antibody to SE-flagella and envelope were significantly higher in the KV group compared to all the other groups. These results suggest that LV protects against SE infection, probably by enhancing the CMI.

Recent progress on the cytokine regulation of intestinal immune responses to Eimeria

A variety of methods are available to combat avian diseases in the commercial setting, including improved farm management practices, use of antibiotic drugs, selection of disease resistant chicken strains, and manipulation of the chicken immune system. In the latter category, development of vaccines against the major avian diseases has become a priority for the poultry industry. With increasing demands for developing alternative control programs for many poultry diseases, it is important to understand the basic immunobiology of host-pathogen interactions in order to develop novel vaccination strategies. From studies carried out in many mammalian species, it is evident that host immune responses to intracellular pathogens are complex and involve many components of the host immune system. For enteric pathogens such as Eimeria and Salmonella, understanding cell-mediated immunity is most important because antibodies, although abundantly produced locally, can not access and act on these intracellular pathogens. In poultry, slow but increasing understanding of various components of host immune system mediating cellular immunity is opening new opportunities for thorough investigation of the role of thymus-derived lymphocyte subpopulations and cytokines in normal and disease states. This paper will review recent progress with chicken cytokines that have been characterized, and discuss various experimental strategies to enhance host immunity to pathogens using chicken cytokines.

Enhanced mucosal immunity against Eimeria acervulina in broilers fed a Lactobacillus-based probiotic

The effect of feeding a Lactobacillus-based probiotic on intestinal intraepithelial lymphocyte (IEL) subpopulations and subsequent protection against coccidiosis was investigated in broiler chickens. Day-old male broilers were fed standard rations without control (CONT) or with a commercial probiotic (PROB) Primalac. Differences in IEL subpopulations were assessed by flow cytometry at 21 d postprobiotic treatment. At 25 d of age, a group of randomly selected birds from each diet was inoculated orally with 10,000 (per bird) sporulated oocysts of Eimeria acervulina and kept on the same diets. Fecal material, sera, and intestinal washes were collected 10 d postchallenge with E. acervulina. Birds on the PROB diet had more IEL expressing the surface markers CD3, CD4, CD8, and alphabetaTCR than those of the CONT diet. The probiotic-fed chickens produced less oocysts (P < 0.0001) compared to the untreated, control group (368 x 10(6) in CONT vs. 89 x 10(6) in PROB). The interferon-gamma levels in both serum and intestinal secretions were not significantly different between the two groups. However, CONT group showed higher antibody levels against a recombinant coccidial antigen in the intestinal secretions than the PROB group. No significant difference was found in serum antibody levels against the same antigen. These results dearly indicate that the probiotic bacteria impacted the local immune response as characterized by altered IEL subpopulations and increased the birds' resistance to E. acervulina as reflected by reduced oocyst shedding.

Effect of vitamin A deficiency on host intestinal immune response to Eimeria acervulina in broiler chickens

The effects of vitamin A (VitA) deficiency on the host intestinal immune response and disease susceptibility to coccidiosis were investigated in broiler chickens following oral infection with Eimeria acervulina (EA). Day-old male broilers were fed milo-soybean meal diets either with 8,000 IU VitA/kg feed (CONT) or without added VitA (A-DEF). At 25 d, a group of randomly selected birds from each treatment was inoculated orally with EA-sporulated oocysts. Intestinal immune response was assessed by the changes in the duodenum intraepithelial lymphocyte (IEL) subpopulations using flow cytometry at 35 d in in fected and noninfected birds. Concanavalin A (ConA)-induced spleen lymphocyte proliferation was tested using dimethylthiazol diphenyltetrazolium bromide colorimetric assay. Whether challenged or not with EA, A-DEF birds had fewer IEL expressing the surface markers CD3, CD4, CD8, alphabetaTCR, and gammabetaTCR. Without EA challenge, A-DEF birds had more surface IgA-expressing cells than CONT birds. Upon challenge, A-DEF chickens showed lower CD4+ IEL than CONT chickens. Following EA infection, CD8+ IEL increased in the CONT group, whereas no change was found in CD8+ IEL of A-DEF birds. A higher number of EA oocysts was recovered from A-DEF birds than from CONT birds (9.2 x 10(8) vs 5.4 x 10(8), respectively; P < or = 0.05). Serum samples taken 10 d post challenge showed higher antibody level against a recombinant coccidial antigen in A-DEF birds than in CONT birds. The A-DEF birds showed depressed ConA-induced lymphoproliferation response and produced lower serum interferon-gamma than CONT birds. These data show that VitA deficiency compromised local immune defenses of challenged birds, as reflected in lymphocyte profiles, oocyst shedding, and interferon-gamma levels in A-DEF birds.