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A series of studies was conducted to determine whether oral tolerance shown to be inducible in rodents can be induced in chickens. A preliminary study was performed with male juvenile Sprague-Dawley rats to ascertain the ability of ELISA to detect oral tolerance induction. Two groups of six rats were provided water with or without 2 mg/mL BSA for 14 consecutive d to induce tolerance. Eight days following water treatment, the rats were challenged i.m. with 1 mg BSA. Serum collected from the rats 20 d later showed decreased (P < .01) anti-BSA ELISA titers in the group given BSA in the water relative to those given ordinary water. Three experiments were conducted to determine whether oral tolerance could be induced in chickens. Birds were given daily oral doses of 25 mg BSA for 14 d (Experiment 1), or fed 5% casein in their diet for 14 d (Experiment 2), or 1 mL of a 50% suspension of SRBC for 10 d (Experiment 3). All birds were challenged with the same antigen after oral dosing. Birds orally dosed with BSA prior to challenge with BSA had titers similar to birds not fed BSA prior to challenge with BSA. When chickens were fed casein (P < .05) or orally gavaged with SRBC (P < .1), titers were enhanced. These observations suggest that feeding antigens prior to injection with the same antigen leads to an enhanced humoral immune response in birds and not tolerance.

The ability of two in vivo tests to assay immune competence of mallard ducks (Anas platyrhynchos) treated with various immunomodulatory agents was examined. Skin responses to phytohemagglutinin-P (PHA-P) injected intradermally and serum antibody levels produced in response to sheep red blood cells (SRBC) were measured. As measured by the skin response to PHA-P, ducks injected intramuscularly with cyclophosphamide or cyclosporine did not respond differently from control-injected ducks. Dexamethasone injected intramuscularly significantly suppressed the skin response to PHA-P. As measured by antibody levels in response to SRBC, ducks injected intramuscularly with cyclophosphamide responded with antibody titers similar to controls. Cyclosporine injected intramuscularly reduced the level of immunoglobulin (Ig) G significantly in one of two experiments. Dexamethasone injected intramuscularly reduced peak total and IgG titers. These experiments provide information on the viability of these two in vivo tests to reflect immune competence of mallard ducks.

Two trials were conducted to compare the effects of supplements of methionine and cysteine on the growth and immune responses of broiler chicks fed corn-soy diets. The basal diet contained 21% crude protein, 3,255 kcal metabolizable energy/kg diet, .35% methionine, .37% cysteine, and .13% choline. Additions to the basal diet were methionine (.063, .25, .85, and 1.45%), or cysteine (.203%), or a combination of methionine (.063%) and cysteine (.153%). Total antibody and 2-mercaptoethanol-resistant antibodies, immunoglobulin G (IgG), were determined in chicks inoculated intraperitoneally at 14 days of age and serially bled at 4, 7, and 10 days postinoculation. Thymus-derived (T)-cell-dependent in vivo mitogen response to phytohemagglutinin-P (PHA-P) was assessed via wing web swelling. The methionine requirement for growth (0 to 3 wk of age) was found to be no more than .413% of the diet (.35% in the basal diet plus .063% added). Addition of 1.45% methionine to the basal diet resulted in significant depression (P less than .05) in growth. The antibody responses generally peaked at 7 days postprimary inoculation. Both methionine and cystine supplementation at low levels resulted in improvement in the cell mediated PHA-P responses as well as in the IgG (T-cell-dependent) responses. High supplemental methionine (1.45%), however, caused significant (P less than .05) depressions in both responses. Equimolar additions of methionine and cysteine (16.8 mmol/kg diet) showed that cysteine was about 84 and 70% as efficacious as methionine in the IgG and the PHA-P stimulation (PHA-I), respectively, in healthy chicks.(ABSTRACT TRUNCATED AT 250 WORDS)

Four experiments were conducted to determine the effect of Na and Cl on the antibody response to sheep red blood cells (SRBC). In the first two experiments, Na and Cl were supplemented in the diet together as NaCl at levels from 0 to .75%. In two additional experiments, Na and Cl were supplemented independently; levels varied from .04 to .24% total dietary Na and from .07 to .36% total dietary Cl. Results of the first two experiments indicated that dietary Na and Cl levels above that found in a corn-soybean diet improved the antibody response to SRBC. Additional studies showed that the humoral immunity was significantly suppressed when chicks consumed diets with less than .14% Na and .17% Cl. Increasing dietary Cl from .17 to .27% when dietary Na was .04% suppressed the antibody response. Also, increasing dietary Cl from .21 to .36% when dietary Na was .14 or .24% suppressed the antibody response. The immunosuppression of the humoral response of chicks was determined to be not related to the decreased feed intake resulting from inadequate Na and Cl in the diet.

Effects of feeding supplementary methionine and choline on broiler growth and immunity were examined by supplementing a corn-soybean diet that contained 21% crude protein, 3,255 kcal metabolizable energy/kg diet, .35% methionine, .37% cystine, and .13% choline. Methionine (.063, .125, .25%) and choline (.125, .25%) were dietary variables. Sulfate (.055%) was added either alone or along with methionine (.125 or .25%) and choline (.125%). In one study, the .25% methionine diet was supplemented with .121% betaine. Sodium and chloride levels were constant in all the diets. Feed and distilled water were supplied ad libitum. Total antibodies, immunoglobulin (Ig) G (2-mercaptoethanol-resistant antibodies) and IgM (2-mercaptoethanol-sensitive antibodies) were determined in 3-wk-old chicks inoculated intraperitoneally with sheep red blood cells. The thymus-derived (T)-cell-dependent in vivo mitogen response to phytohemagglutinin-P (PHA-P) was assessed via wing web swelling. The methionine requirement for growth (0 to 3 wk of age) was approximately .413% of the diet (.35% in the basal diet plus .063% added). Supplementation of the basal diet with .125% choline stimulated growth to the same extent as did the extra .063% of methionine. Addition of .055% sulfate with .125% choline did not improve the ability of the latter to spare methionine. Supplemental methionine resulted in significant (P less than .05) dose-related increases in total antibody, IgG, and response to the mitogen PHA-P, but not in IgM. There were no effects of choline on the immune variables studied. These results suggest that methionine is required for select components of the antibody response, which effect might be related to T-cell help.

Two experiments were conducted to determine the effect of nutritional status, age at weaning and room temperature on growth and immune response of pigs. In the first experiment, 72 pigs were weaned at either 2 or 3 wk and fed either a complex, simple-adequate or simple-inadequate diet for a 24-d period. Total antibody (TAb) titers in response to injections of human red blood cells (RBC) on either 0, 4, or 16 d postweaning were not affected by age at weaning or dietary treatments even though the nutritional status was compromised to such an extent that pigs fed the simple-adequate diet gained at one-half the rate (.172 vs .349 kg/d) of pigs fed the complex or simple-adequate diets (P less than .01). In Exp. 2, the immunological response of 144 pigs weaned at 3 wk were evaluated at 4 and 8 d postweaning. Pigs were weaned into rooms that averaged either 25 or 18 C, and were fed either a complex or simplex-adequate diet at either ad libitum (AL) or restricted (Res) levels for a 24-d period. Restriction of either the complex or simple diet for the first 16 d of the trial drastically reduced (P less than .01) the growth rates of Res pigs compared with AL pigs (.042 vs .236 kg/d). There were no differences in skinfold thickness (Sf) or TAb, 2-mercaptoethanol sensitive (MEs) and resistant (MEr) antibody titers when pigs were inoculated with phytohemagglutinin-P (PHA-P) or RBC at 4 d postweaning regardless of room temperature, diet source or feeding level.(ABSTRACT TRUNCATED AT 250 WORDS)

The growth depression caused by reducing the space allowance in battery brooders from 0.047 to 0.019 m2 per chick was ameliorated by subtherapeutic inclusion rates of dietary antibiotics. However, the interaction of antibiotic supplementation and stocking density was not significant for the variables measured. Increasing stocking density improved the efficiency of food utilisation. The high density regimen resulted in decreased weights of the bursa and thymus relative to body weight but there was no concurrent reductions in antibody response, spleen weight or mortality.