Stress and feather pecking in laying hens in relation to housing conditions

1. Possible association between high rates of feather pecking and increased stress were investigated in laying hens. 2. From week 19 to week 30 after hatching, 16 groups of 11 hens (white Lohman Selected Leghorn hybrids) were kept in pens with or without long-cut straw as foraging material and provided with food in the form of pellets or mash. 3. Stress was assessed by egg production, weight gain, tonic immobility (TI), heterophil/lymphocyte (H/L) ratio and antibody titres to sheep red blood cells (SRBC), tetanus toxoid (TT) and human serum albumin (HSA). 4. Provision of foraging material and food form influenced feather pecking. Rates of feather pecking were highest in groups housed without straw and fed on pellets. 5. Egg production was reduced in pens without straw but not affected by food form. Both the duration of TI and H/L ratios were influenced by provision of foraging material and food form. TI was longer and H/L ratios were increased in hens housed without straw and in those fed on pellets. Antibody titers to SRBC and TT were lower in pens without straw than with straw but not influenced by food form. 6. In conclusion, foraging material and food form affected both feather pecking and indicators of stress, suggesting that feather pecking in laying hens is associated with stress.     

Effect of corticosterone infusion on plasma corticosterone concentration, antibody production, circulating leukocytes and growth in chicken lines selected for humoral immune responsiveness

The effect of corticosterone on antibody production was studied in chicken lines selected for humoral immune response. 2. Twelve cockerels (33 days old) from lines selected for high or low antibody responses after immunisation with sheep red blood cells (SRBC) were implanted with mini-infusion pumps delivering corticosterone or vehicle continuously for 14 d. 3. Three days after implantation, the chickens were immunised intramuscularly with 0.25 ml packed SRBC. Blood samples were taken before implantation, before immunisation and 3, 5, 7 and 11 d after immunization. 4. Corticosterone infusion induced higher plasma corticosterone concentrations and heterophil/lymphocyte ratios than infusion of vehicle only. Growth was considerably depressed and relative weights of the thymus, bursa of Fabricius and spleen were less in the corticosterone-infused chickens. 5. An effect of corticosterone on antibody production could not be demonstrated, and differences between selection lines were unaffected.     

Development of a Delayed-Type Hypersensitivity (DTH) Model in the Cynomolgus Monkey

Although a T-dependent antibody response (TDAR) assay is generally recommended as the first-line immune function assay in nonclinical immunotoxicity evaluation, second-line assays such as delayed-type hypersensitivity (DTH) to measure cell-mediated responses can provide helpful additional information. In this study, male Cynomolgus monkeys were injected intramuscularly either once or twice with 1 mg Keyhole Limpet Hemocyanin (KLH) or twice with a commercially available tetanus vaccine (40 IU tetanus toxoid + 0.06 mg aluminum hydroxide). All animals were subsequently challenged by intradermal injections of the same antigen or aluminum hydroxide after 4, 6 and 8 weeks. Clinical reactions at the injection sites were scored 24, 48 and 72 h post challenge. Skin biopsies were taken on completion of the observation period after each challenge for standard histological examination and immunolabeling using CD3 (T lymphocytes), CD19 (B lymphocytes) and CD68 (macrophages) antibodies. Tetanus toxoid induced stronger clinical reactions than KLH, whereas aluminum hydroxide induced no clinical reaction. Perivascular mononuclear cell infiltrates, a histopathological finding consistent with a DTH reaction, were seen after all challenges with tetanus toxoid or KLH, but not with aluminum hydroxide. Immunohistochemistry evidenced the presence of T lymphocytes and macrophages within these infiltrates. These results suggest that tetanus toxoid adjuvanted with aluminum hydroxide can induce a consistent DTH response for use as a model of cell-mediated response in Cynomolgus monkeys.     

Carry-over effects of dietary yeast RNA as a source of nucleotides on lymphoid organs and immune responses in Leghorn-type chickens

1. The carry-over effects of supplementing Leghorn-type chickens with yeast RNA as a dietary source of nucleotides for 4 weeks on growth, lymphoid organ weights and immune responses were assessed in a 12-week study. 2. A commercial starter feed supplemented with 0 (control), 5 (LR) or 10 (HR) g yeast RNA/kg was offered to 1-d-old male ISA Brown chicks for 4 weeks, and then all birds were given a commercial pullet grower feed for another 8 weeks. Growth performance, antibody responses to sheep red blood cells (SRBC) and cutaneous reactivity of toe webs to phytohaemagglutinin (PHA)-M were measured at 4-week intervals. 3. Growth rates, feed intake and feed efficiency were not affected by dietary yeast RNA during the supplementary period, but birds previously offered the HR diet grew faster than control birds during weeks 4 to 8.4. LR-fed birds had a higher spleen weight relative to body weight (BW) than control birds at week 4, but this effect was not detected at other times. 5. Serum primary antibody levels against SRBC were not affected by dietary yeast RNA at any time. 6. The toe-web PHA response was significantly higher at week 8 in control birds than in birds previously given the LR diet, although no difference among dietary treatments was observed at other times. 7. It is concluded that the addition of yeast RNA as a source of nucleotides to a commercial diet selectively stimulated the development of the spleen in young birds, but this effect did not persist into a later stage of the bird's life.     

The effect of exogenous corticosterone on West Nile virus infection in Northern Cardinals (Cardinalis cardinalis)

ABSTRACT: The relationship between stress and disease is thought to be unambiguous: chronic stress induces immunosuppression, which likely increases the risk of infection. However, this link has not been firmly established in wild animals, particularly whether stress hormones affect host responses to zoonotic pathogens, which can be transmitted to domesticated animal, wildlife and human populations. Due to the dynamic effects of stress hormones on immune functions, stress hormones may make hosts better or poorer amplifying hosts for a pathogen contingent on context and the host species evaluated. Using an important zoonotic pathogen, West Nile virus (WNV) and a competent host, the Northern Cardinal (Cardinalis cardinalis), we tested the effects of exogenous corticosterone on response to WNV infection. Corticosterone was administered at levels that individuals enduring chronic stressors (i.e., long-term inclement weather, food shortage, anthropogenic pollution) might experience in the wild. Corticosterone greatly impacted mortality: half of the corticosterone-implanted cardinals died between five - 11 days post-inoculation whereas only one of nine empty-implanted (control) birds died. No differences were found in viral titer between corticosterone- and empty-implanted birds. However, cardinals that survived infections had significantly higher average body temperatures during peak infection than individuals that died. In sum, this study indicates that elevated corticosterone could affect the survival of WNV-infected wild birds, suggesting that populations may be disproportionately at-risk to disease in stressful environments.     

Corticosterone administration and high-energy feed results in enhanced fat accumulation and insulin resistance in broiler chickens

1. Two experiments were conducted to investigate the effects of exogenous corticosterone administration (30 mg/kg diet) and dietary energy level on feed or energy intake and fat deposition in broiler chickens of 1 and 4 weeks of age. 2. Corticosterone treatment significantly suppressed body weight (BW) gain and reduced feed and caloric efficiencies. The retarded growth may conceal the stimulatory effect of corticosterone on feed consumption or metabolisable energy (ME) intake. A high-energy diet may increase energy intake and partially alleviate the suppressing effect of corticosterone on growth of broilers. 3. Corticosterone administration promoted the conservation of energy stores as fat at both abdominal and subcutaneous sites and this process occurred regardless of dietary energy level in ad libitum feeding status. A high-energy diet increased fat accumulation and showed no significant interaction with corticosterone treatment. 4. The suppressed development of breast and thigh muscles by corticosterone treatment was observed only in 1-week-old chickens fed on the low-energy diet. In contrast, the yield of breast muscle but not thigh muscle was significantly decreased by corticosterone in 4-week-old chickens, suggesting that the tissue specificity to corticosterone challenge is age dependent. 5. Plasma concentrations of glucose, insulin, triglyceride, non-esterified fatty acids (NEFA) and very low density lipoprotein were increased by corticosterone treatment regardless of diet treatment. A high-energy diet increased plasma levels of NEFA and resulted in hyperinsulinism in 4-week-old chickens but not in 1-week-old chickens. 6. Lipoprotein lipase (LPL) activities in adipose tissues may have been up-regulated by corticosterone treatment and showed tissue specificity. The increased LPL activities at ad libitum feeding status were not necessarily linked with the increased fat accumulation in corticosterone challenged chickens. 7. Corticosterone resulted in augmented energy consumption and altered energy redistribution toward lipid deposition. The induced insulin resistance and enhanced hepatic de novo lipogenesis by corticosterone are likely to be responsible for the increased fat deposition.     

Evaluation of bovine cutaneous delayed-type hypersensitivity (DTH) to various test antigens and a mitogen using several adjuvants

The Bacillus Calmette Guerin (BCG)-induced/purified protein derivative (PPD)-elicited tuberculin skin test is a reliable measure of cell-mediated immune response (CMIR), specifically delayed-type hypersensitivity (DTH); however, its use in livestock may confound diagnosis of Mycobacterium tuberculosis. Therefore, various alternative antigen/adjuvant combinations were evaluated as inducers of DTH that were compared to the BCG/PPD test system with the purpose of finding a skin DTH protocol that does not cross-react with the tuberculin test and allows identification of high and low CMIR responder phenotypes. Specifically, 30 non-lactating cows (five/treatment) were sensitized on day 0 with mycobacteria [BCG, M. tuberculosis or Mycobacterium phlei cell wall extract (MCWE)], and ovalbumin (OVA) emulsified in Freund's complete adjuvant (FCA), non-ulcerative Freund's adjuvant (NUFA), complete NUFA or MCWE. On day 21, cows were injected intradermally with various test antigens including PPD tuberculin, phlein, and OVA. Phosphate buffered saline was included as the negative control and the T-cell mitogen phytohemagglutinin (PHA) was also administered. Double skin-fold thickness was evaluated before and at 6, 24, and 48 h post-injection. Skin biopsies were taken at 24 and 48 h to assess oedema, necrosis, and inflammatory cell infiltration. BCG/PPD and M. phlei/phlein treatments when given with a Freund's adjuvant induced equivalent DTH with peak reactions at 24-48 h after antigen injection. Cows receiving NUFA had fewer injection site granulomas than FCA or CNUFA treatments. The change in skin thickness response to PHA peaked at 6 h. Only cows receiving mycobacteria in NUFA had skin response to OVA, which peaked 6-24 h post-injection. Only sites tested with PPD or phlein had significantly higher lymphocyte infiltration than control, whereas neutrophils were significantly higher at PHA test sites and eosinophils predominated at the PHA test sites. Macrophages were significantly more numerous at the PPD and/or phlein test sites in treatment groups that received killed mycobacteria in a Freund's adjuvant and/or with BCG, and at the PHA test sites in all treatment groups. It was concluded that the M. phlei/phlein system did induce DTH and was similar to the DTH induced by the BCG/PPD system when MCWE was administered with a Freund's adjuvant. Therefore, this protocol is suitable for detecting high/low CMIR responders in research herds. However, cross-reaction to PPD was evident following induction of DTH using M. phlei. Hence, this protocol does not alleviate the problem of artificial induction of DTH cross-reactivity and would not be suitable for commercial herds where tuberculin testing is required.     

Effects of the lipopolysaccharide-protein complex and crude capsular antigens of Pasteurella multocida serotype A on antibody responses and delayed type hypersensitivity responses in the chicken.

The effects of the lipopolysaccharide-protein complex (LPS) and crude capsular antigen (CCA) prepared from Pasteurella multocida serotype A isolated from a duck in the Philippines, on antibody responses to sheep red blood cells (SRBC) and Brucella abortus (BA) and delayed type hypersensitivity (DTH) responses to bovine serum albumin (BSA) in the chickens were studied. Chickens injected subcutaneously with LPS and CCA at 1 and 2 weeks of age and immunized intravenously with the mixed antigens of SRBC and BA, at 3 and 4 weeks of age showed significantly increased antibody responses against both SRBC and BA, when evaluated at 7 days after each immunization. In addition, these chickens sensitized intramuscularly with the emulsion of BSA in complete Freund's adjuvant at 5 weeks of age, and then injected into the wattle with BSA at 7 weeks of age also showed significantly increased DTH responses against BSA, when evaluated at 24 and 48 hr after challenge. These results indicate that LPS and CCA of P. multocida serotype A have a property enhancing humoral and cell-mediated immune responses.     

Plasma corticosterone responses to handling in Japanese quail selected for low or high plasma corticosterone responses to brief restraint

1. Plasma corticosterone responses to handling in Japanese quail selected for low or high corticosterone responses to brief mechanical restraint (low and high stress lines) were measured in this study.

2. Initial corticosterone concentrations did not differ between the two lines. Corticosterone concentrations increased 15 min after handling began in quail handled for 5 or 15 min, with greater increases in quail from the high stress than the low stress line. Integrated corticosterone responses were higher in high stress than low stress quail, although the difference between the lines was not significant in quail handled for 5 min.

3. Patterns of plasma corticosterone after 15 min differed between quail handled for 5 or 15 min. Corticosterone increased further or did not change from 15 to 30 min then decreased from 30 to 60 min in quail handled for 5 min, whereas corticosterone decreased from 15 to 30 min then did not change in quail handled for 15 min. Corticosterone concentrations at 60 min remained elevated above initial concentrations, and were similar in quail handled for 5 or 15 min. Corticosterone concentrations at 15 min were more than twice as high in quail handled for 15 min compared with quail handled for 5 min.

4. Although the lines of quail have been selected on the magnitude of corticosterone responses, there was still marked variation in responses between birds within each line. Some quail in the high stress line showed little or no corticosterone response to handling, whilst large responses were seen in some birds of the low stress line. The lines of quail differ in characteristics other than corticosterone responses, including fear behaviour and reproductive development, so the lines provide valuable opportunities to investigate the potential significance of differences between individual birds in their corticosterone responses.     

Vaccination with recombinant NetB toxin partially protects broiler chickens from necrotic enteritis

NetB toxin from Clostridium perfringens is a major virulence factor in necrotic enteritis in poultry. In this study the efficacy of NetB as a vaccine antigen to protect chickens from necrotic enteritis was examined. Broiler chickens were immunized subcutaneously with purified recombinant NetB (rNetB), formalin treated bacterin and cell free toxoid with or without rNetB supplementation. Intestinal lesion scores and NetB antibody levels were measured to determine protection after mild oral gavage, moderate in-feed and heavy in-feed challenges with virulent C. perfringens isolates. Birds immunized with rNetB were significantly protected against necrotic enteritis when challenged with a mild oral dose of virulent bacteria, but were not protected when a more robust challenge was used. Bacterin and cell free toxoid without rNetB supplementation did not protect birds from moderate and severe in-feed challenge. Only birds immunized with bacterin and cell free toxoid supplemented with rNetB showed significant protection against moderate and severe in-feed challenge, with the later giving the greatest protection. Higher NetB antibody titres were observed in birds immunized with rNetB compared to those vaccinated with bacterin or toxoid, suggesting that the in vitro levels of NetB produced by virulent C. perfringens isolates are too low to induce the development of a strong immune response. These results suggest that vaccination with NetB alone may not be sufficient to protect birds from necrotic enteritis in the field, but that in combination with other cellular or cell-free antigens it can significantly protect chickens from disease.     

Influence of selenium on antibody production in sheep

Three experiments were carried out, using sheep fed a marginally low selenium diet, to study the effect of selenium supplementation on the antibody response to tetanus toxoid and on the serum IgG concentration. Six groups of three six-month-old lambs were fed a basal diet containing 0.13 mg Se kg-1 supplemented with either 0.1, 0.5 or 1.0 mg Se kg-1, as sodium selenite or as selenomethionine. These animals generally showed enhanced antibody response to tetanus toxoid, parainfluenza-3 virus and Corynebacterium pseudotuberculosis, and their total serum IgG concentrations were higher than in unsupplemented control animals although few responses were statistically significant. In two field studies significantly higher titres to tetanus toxoid were detected in ewes injected with 100 mg selenium as barium selenate, although no influence on serum IgG concentrations was detected. Lambs from selenium supplemented ewes had significantly higher titres to tetanus toxoid than lambs from ewes in the control group. Dietary vitamin E supplementation had a similar effect on the antibody response to tetanus toxoid in ewes, though no additive effect was seen when vitamin E was given together with selenium.     

Long-term effects of early life L-arginine supplementation on growth performance, lymphoid organs and immune responses in Leghorn-type chickens

The effects of a short-term dietary arginine supplementation after hatching on subsequent growth and the immune system were assessed in growing male Leghorn-type chickens. An arginine-deficient basal diet (67 g/kg) supplemented with 0 (control), 2.7 (LA) or 5.4 (HA) g L-arginine/kg, was offered ad libitum to 1-d-old male ISA Brown chicks for 4 weeks, then all birds were offered ad libitum a commercial pullet grower feed (8.9 g arginine/kg) for another 8 weeks. Supplemented birds had higher growth rates and feed intake than control birds during the 4-week supplementation period, but these effects did not persist into the subsequent periods. When the supplementation ceased at week 4, no differences in lymphoid organ weights relative to body weight (BW), primary serum antibody levels against sheep red blood cells (SRBC) or cutaneous reactivity of toe webs to phytohaemagglutinin (PHA) were detected. LA-fed birds had lower immunoglobulin (Ig) G levels against bovine serum albumin (BSA) than the control at week 4, but this effect did not persist at weeks 8 and 12. No difference in anti-BSA IgM levels was detected among birds at week 4; at week 12, however, the LA-fed birds had a significantly higher anti-BSA IgM level than the control. An increased anti-SRBC antibody level and a reduced relative bursa weight in HA-fed birds were evident at week 8, without any prior effects. It is concluded that short-term supplementary L-arginine had minimal effects on immunity, but some enhancement of SRBC antibody responses in later stages of growth was observed with previous L-arginine administration.     

Involvement of corticosterone in food intake, food passage time and in vivo uptake of nutrients in the chicken (Gallus domesticus)

To evaluate the effect of corticosterone on nutrient transport, 10-week-old male chickens were grouped in 4 categories and treated as follows: sham-operated, adrenalectomised, corticosterone (4 mg/kg injected subcutaneously for 5 d) in both sham-operated and adrenalectomised. The food intake, food passage time and uptake of calcium, phosphorus and glucose were determined by standard procedures. Corticosterone administration to both sham-operated and adrenalectomised groups stimulated significantly higher food intake, delayed food passage time and increased uptake of calcium, phosphorus and glucose, as compared to sham-operated control and adrenalectomised groups. Corticosterone administration increased absorption of these nutrients significantly more in the adrenalectomised group than in the sham-operated controls. Corticosterone also significantly elevated the plasma concentrations of these nutrients. The responses to the hormone were significantly greater in adrenalectomised birds. It is concluded that corticosterone increases food intake and retention and the absorption of calcium, phosphorus and glucose in the alimentary tract.     

Immune responses of Asian elephants (Elephas maximus) to commercial tetanus toxoid vaccine

Although captive elephants are commonly vaccinated annually against tetanus using commercially available tetanus toxoid vaccines marketed for use in horses and livestock, no data exists to prove that tetanus toxoid vaccination produces measurable antibody titers in elephants. An ELISA test was created to measure antibody responses to tetanus toxoid vaccinations in 22 Asian elephants ranging in age from 24 to 56 years (mean age 39 years) over a 7-month period. All animals had been previously vaccinated with tetanus toxoid vaccine, with the last booster administered 4 years before the start of the study. The great majority of elephants had titers prior to booster vaccination, and following revaccination all elephants demonstrated anamnestic increases in titers, indicating that this species does respond to tetanus vaccination. Surprisingly older animals mounted a significantly higher response to revaccination than did younger animals.     

Long-term effects of early-life dietary L-carnitine on lymphoid organs and immune responses in Leghorn-type chickens

The long-term effects of supplementing Leghorn-type chickens with dietary L-carnitine after hatching for 4 weeks on growth, lymphoid organ weights, humoral and cell-mediated immune responses were assessed in a 12-week study. A commercial starter feed supplemented with 0 (control), 100 (LC) or 1,000 (HC) mg L-carnitine/kg was offered to day-old ISA Brown cockerels for 4 weeks, then all birds were given a commercial pullet grower feed for another 8 weeks. No differences (p > 0.05) in growth rates, feed intake or feed utilisation efficiency existed among the dietary treatments throughout the study. Compared with control birds, HC-fed birds had a lower (p < 0.05) thymus weight relative to bodyweight (BW) at Week 4, but a higher (p < 0.05) relative thymus weight at Week 12. A higher (p < 0.05) serum primary antibody response to sheep red blood cells (SRBC) in HC-fed birds than in the other two groups was also detected at Week 12. Relative spleen or bursa weights and cutaneous responses of toe webs to phytohaemagglutimin (PHA) (an in vivo indicator of cell-mediated immune responses) did not differ (p > 0.05) among dietary treatments at any time. It is concluded that a short-term supply of dietary L-carnitine to a conventional commercial feed after hatching enhanced subsequent humoral immunity in Leghorn-type chickens. Further study is warranted to confirm such a long-term effect.     

Effect of reovirus infection and dietary levels of selected vitamins on immunocompetence of chickens

The immunocompetence of 8-week-old reovirus WVU 2937-infected and uninfected chickens fed various dietary levels of biotin, niacin, choline, or folic acid was evaluated in four experiments. Antibody production to sheep red blood cells (SRBC), wattle responses to phytohemagglutinin-P (PHA-P), and wattle responses of tuberculin-sensitized chickens to bovine-purified protein derivative (PPD) were examined in five chickens per treatment. Dietary deficiencies had no effect on the in vivo T-cell immune responses to PPD, PHA-P, or humoral hemagglutinating-antibody production to SRBC. Reovirus-infected and uninfected chickens fed biotin at double the National Research Council (1977) requirement demonstrated decreased PPD responses. Lower hemagglutinating-antibody titers in the uninfected chickens and increased titers in the infected chickens were observed in those fed 200% of the requirement of biotin when compared with the chickens fed 20% and 100% biotin diets. Reovirus infection had no effect on PPD and PHA-P responses. However, in the choline experiment, reovirus-infected chickens had elevated titers. These data indicate that reovirus infection had no adverse effect on the immunocompetence of chickens 8 weeks postinfection. Dietary deficiencies also had no adverse effect on the immunocompetence of 8-week-old reovirus-infected and uninfected chickens.     

Behaviour and welfare of individual laying hens in a non-cage system

1. A leg band containing a transponder was fitted to 80 birds in a perchery containing 1,000 birds. 2. The transponder emitted a unique identification number when a bird walked on one of 8 flat antennae on the floor. The recording apparatus was used to measure the amount of time that each of the tagged birds spent on the slatted and littered areas in a 6-week period. 3. Some birds spent long periods of time on the slats, possibly as a means of avoiding repeated attacks. Duration on the slats was greatest in birds with the worst (as opposed to better) feather scores of the head, back and tail regions. 4. Birds that spent long periods on the slats were lighter than other birds at both 39 weeks of age and 72 weeks of age and had greater back, head and tail feather damage, consistent with these birds being victims of pecking. 5. Tagged birds received a social avoidance test outside the perchery at 39 weeks of age, which suggested that birds retreated to the slats in response to pecks rather than just to close proximity to other birds. 6. The failure to find that duration on the slats was related to anatomical indicators of stress (liver, spleen and bursa of Fabricius) suggests that retreating to the slats following pecking attenuates physiological stress responses. 7. We conclude that the provision of areas where birds in a large group can avoid pecking may improve the welfare of a minority of victimised birds.     

Response to Eimeria tenella of chickens selected for high or low antibody response and differing in haplotypes at the major histocompatibility complex.

Sublines of chickens selected for high antibody (HA) or low antibody (LA) response that differed at the major histocompatibility complex (MHC) were tested for response to Eimeria tenella. In Expt. 1, the first exposure to E. tenella was natural (in floor pens), and chicks were challenged orally 21 days later with 0, 928, or 1855 oocysts. In Expt. 2, chicks were reared in wire-floored batteries, vaccinated orally with 928 oocysts, and challenged orally 12 days later with 15,844 oocysts. Corticosterone (20 mg/kg) was mixed with feed from 24 hr before vaccination to 120 hr after vaccination in Expt. 2. In Expt. 1, LA chicks had more-severe cecal lesions but gained relatively more body weight after challenge than did HA chicks. In Expt. 2, cecal lesions were least severe in HA chicks that had been fed corticosterone, most severe in LA chicks fed corticosterone, and intermediate in chicks that were not fed corticosterone. No differences in response to E. tenella occurred as a result of haplotypes at the MHC.     

Social stress and resistance of chicken and swine to Staphylococcus aureus challenge infections.

The purpose of this research was to determine the effect of social stress on the susceptibility of chickens and swine to Staphylococcus aureus infection. Chickens were housed under four levels of social stress. Weaned pigs remained with their litter or were housed separately. One day after some birds were placed in the high stressed environments all were challenged intravenously with S. aureus. Susceptibility was characterized by joint infection in swine and reduced weight gain in chickens. Chickens which were moved into the high stressed environments before challenge lost weight while the controls gained weight (P less than 0.001). During the three days postchallenge the most severely stressed chickens lost less than half as much body weight as did the least stressed (P less than 0.001). During the post-challenge period chickens selected for high corticosterone response in a high social stress gained weight while chickens selected for a low corticosterone response in a low stress environment lost weight (P less than 0.0001). Swine housed under a reduced level of stress (social) were more susceptible to S. aureus than those kept under higher levels of stress (P = 0.0001).     

Steroidogenic properties of isolated adrenocortical cells from Japanese quail selected for high serum corticosterone response to immobilization

The effect of selection for high stress response on adrenocortical function was examined by measuring the corticosterone response of adrenocortical cells isolated from random-bred Japanese quail and quail selected for high serum corticosterone response to immobilization (high-stress). Highly enriched adrenocortical cells were incubated with various concentrations of ACTH1-24 (ACTH), 8-bromo-cyclic AMP (8Br-cAMP) and pregnenolone for 2 hr. Corticosterone production was measured by radioimmunoassay. Basal corticosterone production values by cells from random-bred and high-stress birds were not different. In contrast, the average maximal ACTH- and 8Br-cAMP-induced corticosterone production by cells from high-stress quail was 89% greater than that of cells from random-bred quail. However, the average pregnenolone-supported corticosterone production by cells from high-stress birds was 34% less than that of cells from random-bred birds. Thus, the data suggest that although random-bred quail cells had a greater potential capacity for corticosterone production, high-stress quail cells had a greater ability to couple ACTH, ACTH-transmembrane-signaling factors and subsequent second messengers with the available steroidogenic enzyme pool. The magnitude of the differences in function between cells from high-stress and random-bred birds was greater for female cells compared to male cells. In addition to differences in cellular function, there were also differences in adrenal and relative adrenal weights between random-bred and high-stress quail. The average, adrenal and relative (mg/100 g body weight) adrenal weights of high-stress quail were 14-16% greater than those of random-bred quail. It is concluded that the enhanced serum corticosterone response of the high-stress quail line is, in part, due to an increase in relative adrenal weight and an increase in adrenocortical cell responsiveness to ACTH.