Inheritance of antibody response to sheep erythrocytes in lines of chickens divergently selected for fifty-six-day body weight and their crosses

Differing Expression and Potential Immunological Role of C-Type Lectin Receptors of Two Different Chicken Breeds against Low Pathogenic H9N2 Avian Influenza Virus

Diverse immune responses in different chicken lines can result in varying clinical consequences following avian influenza virus (AIV) infection. We compared two widely used layer breeds, Lohmann Brown (LB) and Lohmann White (LW), to examine virus replication and immune responses against H9N2 AIV infection. The transcription profile in the spleen of H9N2-infected chickens was compared using a microarray. Confirmatory real-time RT-PCR was used to measure the expression of C-type lectin, OASL, and MX1 genes. Additionally, to investigate the role of chicken lectin receptors in vitro, two C-type lectin receptors (CLRs) were expressed in DF-1 cells, and the early growth of the H9N2 virus was evaluated. The LB chickens shed a lower amount of virus from the cloaca compared with the LW chickens. Different expression levels of C-type lectin-like genes were observed in the transcription profile, with no significant differences in OASL or MX gene expression. Real-time RT-PCR indicated a sharp decrease in C-type lectin levels in the spleen of H9N2-infected LW chickens. In vitro studies demonstrated that cells overexpressing CLR exhibited lower virus replication, while silencing of homeostatic CLR had no effect on AIV replication. This study demonstrated distinct immune responses to H9N2 avian influenza in LB and LW chickens, particularly with differences in C-type lectin expression, potentially leading to lower virus shedding in LB chickens.

Genotype-dependent development of cellular and humoral immunity in the spleen and cecal tonsils of chickens stimulated in ovo with bioactive compounds

Prebiotics, probiotics, and synbiotics, delivered in ovo influence the colonization and development of the peripheral immune system in poultry. This study aimed to investigate the influence of the host genotype (broiler chickens [Ross 308] and old native Polish breed Green-legged Partridgelike [GP] chickens) on the number of B and T cells in the spleen and cecal tonsils (CT). The solution of a bioactive compound was injected in ovo on day 12 of egg incubation: prebiotics (galactooligosaccharides [GOS]), probiotics (Lactococcus lactis subsp. cremoris IBB477), and synbiotics (GOS + L. lactis). The samples were collected on day 7, day 21, and day 42 after hatching (n = 8). The number of Bu-1⁺ (B) cells, CD4⁺ cells, and CD8⁺ cells in the spleen and CT was estimated using immunohistochemistry. The number of germinal centers (GC) was determined in the spleen. In broilers, probiotics increased (P < 0.05) the number of CD4⁺ cells in the CT on day 7. On day 21, prebiotics raised (P < 0.01) the number of cells involved in cellular immunity in the CT (CD4⁺ and CD8⁺ cells) and spleen (CD8⁺ cells). On day 42, it was synbiotics that stimulated the colonization of both the CT and spleen by B cells, but colonization of the spleen only by CD4⁺ and CD8⁺ cells. In GP chickens, synbiotics enforced the cellular immunity (CD4⁺ or CD8⁺ cells) in the spleen at all time points. Synbiotics also stimulated the GC appearance on day 21 and day 42. In GP chickens, the influence of bioactive compounds on colonization of the CT was very limited. In broilers, we determined pronounced and age-dependent effects of prebiotics and synbiotics on the number of B and T cells in both the CT and spleen. In GP chickens, the most potent compound was synbiotics, which stimulated cellular immunity in the spleen but not in the CT. However, given the long-term effects on adaptive immune cells, synbiotics were the most potent compounds in both chicken genotypes.

Immune responses upon in ovo HVT-IBD vaccination vary between different chicken lines

The genotype of chickens is assumed to be associated with variable immune responses. In this study a modern, moderate performing dual-purpose chicken line (DT) was compared with a high-performing layer-type (LT) as well as a broiler-type (BT) chicken line. One group of each genotype was vaccinated in ovo with a recombinant herpesvirus of turkeys expressing the virus protein VP2 of the infectious bursal disease virus (HVT-IBD) while one group of each genotype was left HVT-IBD unvaccinated (control group). Genotype associated differences in innate and adapted immune responses between the groups were determined over five weeks post hatch. HVT-IBD vaccination significantly enhanced humoral immune responses against subsequently applied live vaccines compared to non-HVT-IBD vaccinated groups at some of the investigated time points (P < 0.05). In addition HVT-IBD vaccination had depending on the genotype a significant impact on splenic macrophage as well as bursal CD4⁺ T-cell numbers (P < 0.05). On the other hand, the detectable genotype influence on Interferon (IFN) γ and nitric oxide (NO) release of ex vivo stimulated spleen cells was independent of HVT-IBD vaccination. The results of our study suggest considering a genotype specific vaccination regime in the field.

Dwarf chickens with low monocytes/macrophages phagocytic activity show low antibody titers but greater performance

Monocytes/macrophages phagocytosis has key roles in inflammatory responses. However, systematic research on the effects of monocytes/macrophages phagocytosis on production and reproductive performance in dwarf chickens is lacking. In this study, we developed the HCT-8-MTT method to detect monocytes/macrophages phagocytosis product (PP) which was accuracy, flexible, and saving time. Based on PP in 990 dwarf chickens (890 hens and 100 cocks), chickens were divided into high phagocytosis product group (HPPG) and low phagocytosis product group (LPPG). In production performance, chickens in LPPG have higher laying rate at 24 wk and 71 wk and higher average egg weight at 23 wk and 24 wk than in HPPG (P < 0.05). The levels of follicle-stimulating hormone and luteinizing hormone were higher in LPPG than in HPPG at 58 wk (P < 0.01). In the reproductive performance, the fertilization rate in LPPG was higher than that in HPPG at 45 wk, 49 wk, and 53 wk (P < 0.05). Chickens in LPPG have higher hatchability than HPPG at 45 wk and 49 wk (P < 0.05). In LPPG, the mRNA expression levels of follicle-stimulating hormone receptor and CD9 in the follicle were higher than HPPG (P < 0.05). In the immune response, chickens with higher PP levels showed higher antibody titers for the avian influenza virus H9 inactivated vaccine (P < 0.01). Therefore, monocytes/macrophages PP was positively associated with antibody titers and negatively related to production and reproductive performance, and these findings have practical applications for the optimization of production in the poultry industry.

Immunocompetence and resistance to marble spleen disease of broiler- and layer-type pure lines of chickens

The intent of this study was to evaluate, under concurrent conditions, certain responses that may be important in chicken breeding and growing. Three commercial broiler pure lines (A, B, and C) and two experimental White Leghorn lines selected for high (HAS) and low (LAS) antibody response to sheep red blood cells were evaluated concurrently for humoral and cell-mediated immunocompetence, resistance to marble spleen disease virus (MSDV), relative asymmetry (RA), and comb weight. Chicks were injected with 0.1 ml of 0.25% SRBC at 21 days of age. Antibody response 6 days after injection was highest in line HAS. Titres for the commercial lines were similar to those in line LAS. The cutaneous basophil hypersensitivity test, an in vivo cell-mediated immune response, was measured as the increase in toe-web thickness 24 h after an injection with T-cell mitogen phytohaemagglutinin (PHA)-P or -M into a sample of chicks at 9 days of age and a different sample of chicks at 20 days of age. PHA-P elicited greater responses than PHA-M at both ages. The pattern among stocks, however, differed depending upon age. Responses at 9 days were greater for the Leghorn than broiler lines, while at 20 days, responses were greater in lines A and LAS than in lines B, C, and HAS. Resistance to MSDV challenge differed among stocks, with the ranking for resistance being C>(A=B=LAS)>HAS. Rankings of RA for normal thickness of the toe web between the third and fourth digits at 9 days of age were (HAS=LAS)>(A=B=C). There were no differences in RA among stocks at 20 days of age. There was a significant line by sex interaction for relative comb weight, due to differences between lines for males but not females. Data from this study suggest that competence in one arm of the immune system is not a reliable measure of general immunocompetence, nor is it a measure of resistance in general.

Transcriptomic and Epigenetic Profiling of the Lung of Influenza-Infected Pigs: A Comparison of Different Birth Weight and Susceptibility Groups

Influenza viruses are a common cause of respiratory disease in swine. Infections range in severity from asymptomatic to causing significant morbidity. The main objective of this study was to compare lung transcriptomic and epigenetic responses to influenza infection in pigs from high or low birth weight litters. The latter is a potential indicator of intrauterine growth restriction, a significant risk factor for prenatal programming effects. Individual pigs from high (HBW) or low birth weight (LBW) litters (n = 17) were inoculated with influenza A virus and euthanized 48 hours later. Lesion severity and viral loads were assessed as previously described. The transcriptional response to infection in LBW and HBW groups (n = 16) was assessed by microarray. A separate analysis of pigs classified as 'Resilient' (RES) or 'Susceptible' (SUS) (n = 6) on the basis of severity of lung pathology was also conducted. Eight genes were confirmed as differentially expressed for the birth weight comparison, including three antiviral genes with lower expression in LBW: ISG15, OAS1, and OAS2 (P<0.05). The promoter region methylation status of these three genes was assessed for each birth weight group, and no differences were found. These expression data are consistent with our previous finding that LBW pigs had less severe lesion scores and a trend towards lower viral titres in lung than the HBW cohort. The SUS v RES comparison identified 91 differentially expressed genes (FDR<0.05) that were enriched with functional annotation terms and pathways associated with inflammation. The cytokine genes IL6, IL8, and CCL2 were all upregulated in SUS pigs, and may have driven disease severity in these animals. In conclusion, this study found no evidence that the transcriptional immune response to influenza was adversely affected by low litter birth weight, but did identify several candidate genes for driving disease pathology.

Effects of Long-term Graded L-arginine Supply on Growth Development, Egg Laying and Egg Quality in Four Genetically Diverse Purebred Layer Lines

The present study was conducted to examine effects of long-term graded L-arginine supply on growth development, egg laying and egg quality in four genetically diverse purebred layer lines. The study comprised a rearing trial from hatch to week 16 and a following laying performance trial from week 17 to 41. After hatch 150 one-day-old female chicks of each genotype were distributed to three diets. The experimental diets were equivalent to 70, 100 and 200% L-arginine of age-specific recommended level (National Research Council, 1994) and were offered ad libitum to chicks (hatch to week 7), pullets (week 8 to 16) and hens (week 17 to 41). However, hens' diets were quite low in crude protein. After a pre-laying period from week 17 to 21 thirty-six pullets of each group were used further in the laying performance trial. Independent of chicken's genetic background, insufficient L-arginine supply caused lower body weight, daily weight gain and daily feed intake during the rearing (p<0.001) and induced lower laying intensity and daily egg mass production in the laying period (p<0.05). Parameters fitted to Gompertz function suggested higher adult body weight in L-arginine supplemented birds compared to insufficient supplied ones (p<0.01). Groups fed with insufficient L-arginine reached age of maximum daily weight gain later and showed lowest maximum daily weight gain (p<0.001). As a consequence of limitations in dietary L-arginine and crude protein, high performing genotypes decreased strongly in body weight, daily feed intake and performance compared to the low performing genotypes. In conclusion, L-arginine modified the amount of weight gain and feed intake, especially in growing chicks and pullets independent of genetic background. The high performing hens were more nutritionally stressed than the low performing ones, because concentrations of dietary crude protein were relatively low.

Relative disease susceptibility and clostridial toxin antibody responses in three commercial broiler lines coinfected with Clostridium perfringens and Eimeria maxima using an experimental model of necrotic enteritis

Necrotic enteritis is an enteric disease of poultry resulting from infection by Clostridium perfringens with coinfection by Eimeria spp. constituting a major risk factor for disease pathogenesis. This study compared three commercial broiler chicken lines using an experimental model of necrotic enteritis. Day-old male Cobb, Ross, and Hubbard broilers were orally infected with viable C. perfringens and E. maxima and fed a high-protein diet to promote the development of experimental disease. Body weight loss, intestinal lesions, and serum antibody levels against alpha-toxin and necrotic enteritis B-like (NetB) toxin were measured as parameters of disease susceptibility and host immune response. Cobb chickens exhibited increased body weight loss compared with Ross and Hubbard breeds and greater gut lesion severity compared with Ross chickens. NetB antibody levels were greater in Cobb chickens compared with the Ross or Hubbard groups. These results suggest that Cobb chickens may be more susceptible to necrotic enteritis in the field compared with the Ross and Hubbard lines.

Immune response from a resource allocation perspective

The immune system is a life history trait that can be expected to trade off against other life history traits. Whether or not a trait is considered to be a life history trait has consequences for the expectation on how it responds to natural selection and evolution; in addition, it may have consequences for the outcome of artificial selection when it is included in the breeding objective. The immune system involved in pathogen resistance comprises multiple mechanisms that define a host's defensive capacity. Immune resistance involves employing mechanisms that either prevent pathogens from invading or eliminate the pathogens when they do invade. On the other hand, tolerance involves limiting the damage that is caused by the infection. Both tolerance and resistance traits require (re)allocation of resources and carry physiological costs. Examples of trade-offs between immune function and growth, reproduction and stress response are provided in this review, in addition to consequences of selection for increased production on immune function and vice versa. Reaction norms are used to deal with questions of immune resistance vs. tolerance to pathogens that relate host health to infection intensity. In essence, selection for immune tolerance in livestock is a particular case of selection for animal robustness. Since breeding goals that include robustness traits are required in the implementation of more sustainable agricultural production systems, it is of interest to investigate whether immune tolerance is a robustness trait that is positively correlated with overall animal robustness. Considerably more research is needed to estimate the shapes of the cost functions of different immune strategies, and investigate trade-offs and cross-over benefits of selection for disease resistance and/or disease tolerance in livestock production.

Bovine respiratory disease in feedlot cattle: phenotypic, environmental, and genetic correlations with growth, carcass, and longissimus muscle palatability traits

Bovine respiratory disease (BRD) is the most costly feedlot disease in the United States. Selection for disease resistance is one of several possible interventions to prevent or reduce the economic loss associated with animal disease and to improve animal welfare. Undesirable genetic relationships, however, may exist between production and disease resistance traits. The objectives of this study were to estimate the phenotypic, environmental, and genetic correlations of BRD with growth, carcass, and LM palatability traits. Health records on 18,112 feedlot cattle over a 15-yr period and slaughter data on 1,627 steers over a 4-yr period were analyzed with bivariate animal models. Traits included ADG, adjusted carcass fat thickness at the 12th rib, marbling score, LM area, weight of retail cuts, weight of fat trim, bone weight, Warner-Bratzler shear force, tenderness score, and juiciness score. The estimated heritability of BRD incidence was 0.08 +/- 0.01. Phenotypic, environmental, and genetic correlations of the observed traits with BRD ranged from -0.35 to 0.40, -0.36 to 0.55, and -0.42 to 0.20, respectively. Most correlations were low or negligible. The percentage of carcass bone had moderate genetic, phenotypic, and environmental correlations with BRD (-0.42, -0.35, and -0.36, respectively). Hot carcass weight and weight of retail cuts had moderate, undesirable phenotypic correlations with BRD (0.37 and 0.40, respectively). Correlations of BRD with LM palatability and ADG were not detected. Low or near zero estimates of genetic correlations infer that selection to reduce BRD in feedlot cattle would have negligible correlated responses on growth, carcass, and meat palatability traits or that selection for those traits will have little effect on BRD susceptibility or resistance.

Immune response to a killed infectious bursal disease virus vaccine in inbred chicken lines with different major histocompatibility complex haplotypes

The influence of MHC on antibody responses to killed infectious bursal disease virus (IBDV) vaccine was investigated in several MHC inbred chicken lines. We found a notable MHC haplotype effect on the specific antibody response against IBDV as measured by ELISA. Some MHC haplotypes were high responders (B201, B4, and BR5), whereas other MHC haplotypes were low responders (B19, B12 and BW3). The humoral response of 1 pair of recombinants isolated from a Red Jungle Fowl (BW3 and BW4) being identical on BF and BG, but different on BL, indicated that part of the primary vaccine response was an MHC II restricted T-cell dependent response. The humoral response in another pair of recombinant haplotypes originating in 2 different White Leghorn chickens being BF21, BL21, BG15 (BR4) and BF15, BL15, BG21 (BR5) on the MHC locus indicated that the BG locus may perform an adjuvant effect on the antibody response as well. Vaccination of chickens at different ages and in lines with different origin indicated that age and background genes also influence the specific antibody response against inactivated IBDV vaccine.

Relationship Between Immune Cell Phenotypes and Pig Growth in a Commercial Farm

The objective of this study was to evaluate the relationship between the level and function of circulating immune cells with average daily gain, live and carcass measurements, feed intake, and feed conversion. Production performance was monitored throughout the pig's lifetime. Pigs were moved in weekly batches through the nursery and growing/finishing rooms at specific target weights. Animals were individually weighed at birth and at weaning, and then every two weeks while they were "on test" until they were "off test" and sent to the slaughterhouse. At six to seven weeks of age, the pigs were bled in the nursery. The percentage of immune cell subsets and lymphocyte proliferation was estimated using swine monoclonal antibodies and flow cytometric analysis. The predictive effect of the immune cell subset markers and lymphocyte proliferation on production traits was statistically analyzed. The results indicated that the proportion of several peripheral cell subsets, including CD16+, CD2+/CD16+, and CD8+ lymphocytes, appear to predict growth during the entire productive life of the pig. Larger percentages of lymphocytes expressing CD16+ CD2+/CD16+, and CD8+receptors in blood resulted in a reduction in average daily gain. In addition, high percentages of SLA-DQ+ cells were associated with better carcass weight and feed conversion. The CD16+, CD2+/CD16+, CD8+, and SLA-DQ+/- cell subsets appear to be important biomarkers involved with the inherent ability of the pig to efficiently grow and produce better carcass weight in representative commercial environments.

Genetic variation in major histocompatibility complex class I alpha2 gene among broilers divergently selected for high or low early antibody response to Escherichia coli

The MHC genes have a profound effect on animal abilities to respond to specific antigens because they play a role in presenting foreign antigens to T cells during the course of the humoral or cellular immune response. In the current study, polymorphism in the MHC class I alpha2 domain was compared in 2 lines divergently selected for high (HH) or low (LL) antibody response to Escherichia coli vaccine. These lines also differ markedly in their antibody response to natural E. coli exposure and to vaccination with Newcastle disease virus, infectious bronchitis virus, and infectious bursa disease virus. Recent trials have shown that the LL chicks exhibit a significantly higher percentage of CD8+ T lymphocytes in their peripheral blood lymphocytes and spleen than HH chicks. Despite symmetrical selection intensity in both lines, polymorphism of the alpha2-domain gene was higher in the LL line than in the HH line. Among 29 single-nucleotide polymorphism positions found, 3 were unique to the HH line, 15 were unique to the LL line, and 11 were polymorphic in both lines. These single nucleotide polymorphism positions were not 100% line specific and were in agreement with the genetic variation in antibody level or cellular response still found within the selection lines. Five amino acid positions showed significant differences in polymorphism between the selection lines. These were located within the antigen-binding cleft, suggesting that these positions might influence the ability of MHC class I to bind foreign antigens and leading to differences in immunocompetence between the lines.

Use of Conjoint Analysis to Weight Welfare Assessment Measures for Broiler Chickens in UK Husbandry Systems

For the purposes of farm animal welfare assessment, Farm Assurance Schemes and enforcement of animal welfare legislation, a requirement arises for a unitary welfare score which may be the amalgamation of several animal welfare measures. In amalgamating measures, weighting to reflect the importance of the individual measures for animal welfare is desirable. A study is described in which conjoint analysis was used to collect and evaluate expert opinion to weight a number of welfare assessment measures for the importance of each to broiler welfare in UK husbandry systems. The statistically combined opinion of the experts consulted revealed the weighting factors of the welfare assessment measures selected, with respect to the importance for bird welfare, to be: 0.26 for mortality levels on the growing unit; 0.24 for the level of leg weakness; 0.16 for the level of hock burn; 0.14 for stocking density; 0.10 for enrichment provision; and, 0.10 for the level of emergency provision. Criteria for selection of welfare assessment measures for use in the field, and level of agreement between experts consulted for the study, are discussed. It is concluded that weightings of welfare assessment measures by expert opinion, using conjoint analysis, might be used in the construction of a welfare index for assessment of broiler welfare on-farm. Such an index should not be considered as a ‘gold standard’ for welfare measurement but as an evolving standard for welfare assessment, based on current knowledge.

A comparison of the immune response of a 2001 commercial broiler with a 1957 randombred broiler strain when fed representative 1957 and 2001 broiler diets

Immunocompetence of the 2001 Ross 308 broiler strain and the 1957 Athens Canadian Randombred Control (ACRBC) strain was compared when they were given diets representative of those that were being used in 1957 and 2001. Antibody response against SRBC, in vivo lymphoproliferation against Phytohemagglutinin-P (PHA-P), and inflammatory and phagocytic responses of the macrophages were measured. The Ross 308 strain on the 2001 diet had higher BW at 24 d of age (P = 0.0001), whereas the ACRBC had greater lymphoid organ weights (except thymus) relative to BW (P < or = 0.003). The ACRBC strain showed greater antibody responses against SRBC than the 2001 Ross 308 birds for much of the trial (P < or = 0.0362). However, the Ross 308 broilers had greater PHA-P-induced toe-web swelling response (P < or = 0.0129). Inflammatory exudate cell numbers were higher in the Ross 308 broilers than in the ACRBC birds (P = 0.0261). The percentage of macrophages that phagocytized SRBC was comparable between the two strains, but the number of SRBC phagocytized by individual macrophages was higher (P = 0.0122) in the Ross 308 broiler than in the ACRBC chickens. Nitrite production by macrophages following lipopolysacharide stimulation was comparable between the two strains. Interactions of diet, strain, and sex were inconsistent among all parameters tested. In conclusion, the current study suggested that genetic selection for improved broiler performance has resulted in a decrease in the adaptive arm of the immune response but an increase in the cell-mediated and inflammatory responses.

Immunological differences between layer- and broiler-type chickens

In commercial poultry husbandry, alternatives for the use of antibiotics and vaccines are under investigation, which preferably have to be applicable for both layer- and broiler-type chickens. There are indications that the defense mechanisms vary between layer- and broiler-type chickens. Therefore, the difference in immune response between layer- and broiler-type chickens of the same age was investigated, using TNP-KLH (trinitrophenyl-conjugated keyhole limpet hemocyanin) as antigen without adjuvant. First different routes of immunization (intravenously, intramuscular, subcutaneous and ocular) were examined to find out which immunization route gives the highest antibody titers. The intravenous immunization route resulted in higher TNP-specific antibody responses than the other immunization routes tested and therefore this immunization route was used in both following experiments. In order to investigate the optimal dose of antigen needed for immunization, a dose-response curve in broiler- and layer-type chickens was completed. The humoral immune response was measured in serum by a TNP-specific ELISA and the in vitro cellular immune response by an antigen-specific lymphocyte proliferation assay. The antibody response of layer- and broiler-type chickens appeared to differ, not only in optimal dose and response, but also in kinetics of the response itself. Broiler chickens generated higher IgM anti-TNP titers whereas layer-type chickens generated higher IgG anti-TNP titers. This specific antibody response in broiler-type chickens did not last as long as in layer-type chickens. The TNP-specific cellular immune response was detectable in layer-type chickens, but not in broilers. Both types generate a non-specific cellular immune response, although this response in broilers is lower than in layer-type chickens. From these results, we conclude that broilers primarily respond to TNP-KLH with a high IgM antibody response whereas layer-type chickens respond with a high IgG response. In addition, the cellular response of layer-type chickens is much higher than the response of broilers. The results suggest that broilers are specialized in the production of a strong short-term humoral response and layer-type chickens in a long-term humoral response in combination with a strong cellular response, which is in conformity with their life expectancy.

Phenotypic variation among three broiler pure lines for Marek's disease, coccidiosis, and antibody response to sheep red blood cells

To identify candidate genes, chicken lines with the most divergent phenotypes are usually crossed to generate resource mapping populations, for example, either backcrossed or F2 populations. Linkage between the genetic marker and the phenotypic trait locus is then tested in the mapping population. As an initial step in the development of a mapping population from commercial broilers, the goal of the current research was to evaluate the phenotypic variation among three pure lines for antibody response to SRBC and in resistance to two economically important poultry diseases, Marek's disease (MD) and coccidiosis (Eimeria acervulina). Chicks from each line were received and separated into three experimental studies to evaluate each of their responses. In summary, broiler Line 3 had significantly lower antibody responses to SRBC immunizations compared to the other two lines, and nonvaccinated birds from Line 3 were also more susceptible to MD. With coccidiosis, the response was complex, and ranking of the lines was dependent on the age of infection, and whether it was a first or second challenge. With the first challenge, Line 1 was most susceptible at the younger age (Day 30), whereas Line 3 was susceptible at the older age (Day 58). Upon the second challenge, broiler Line 1 remained susceptible at the younger age, but Line 2 was more susceptible at the older age. Line 3 was completely resistant to the second challenge at the older age. Thus, although the broiler lines have been intensively selected for productivity and general livability, this study also demonstrates that the lines differ for immune response and disease resistance. Based on the phenotypic differences between Lines 1 and 3, they were chosen to establish a mapping population for identifying candidate genes that affect MD and coccidiosis in commercial broiler chickens.

The dynamics of antibody response to Escherichia coli vaccination in meat-type chicks

The dynamics of serum antibody (Ab) response in young broilers were studied in lines divergently selected for high (HC) or low (LC) Ab response to Escherichia coli vaccination at an early age, and their cross (HL). Chicks were divided into three vaccination-age (VA) groups: 8, 10, and 12 d of age (VA8, VA10, and VA12, respectively). Antibody response was determined five times for each chick, at 6, 8, 10, 12, and 14 d postvaccination (dPV). The effects of line, VA, and dPV on Ab titers were highly significant. The HC and LC chicks exhibited the highest and lowest mean titers, respectively, in all VA groups. The HL chicks exhibited midparent Ab values for all VA and dPV combinations, indicating additive inheritance of early Ab production. In LC, the highest mean Ab titer was obtained on Day 26 (14 dPV of the VA12 group), whereas in HC, the same titer had already been obtained on Day 18 (VA8-10 dPV and VA10-8 dPV combinations). The VA8 and VA12 chicks differed markedly in their Ab titer dynamics curves, and the VA10 chicks exhibited an intermediate curve. The three VA groups exhibited a similar change in Ab level from 6 to 10 dPV, but they differed in Ab change from 10 to 14 dPV. This significant dPV x VA interaction suggests that the VA12 and VA10, but not VA8, chicks maintained the capability to produce persisting Ab.

Antibody responses to sheep red blood cell and Brucella abortus antigens in a turkey line selected for increased body weight and its randombred control

Turkeys from a randombred control line (RBC2) and its subline (F) selected for increased 16-wk BW were tested for primary and secondary antibody responses to SRBC antigen and Brucella abortus antigen (BA). Previous studies have shown that the F line was more susceptible to Pasteurella multocida and Newcastle disease virus than was the RBC2 line. Individuals from the RBC2 and F lines were intravenously injected with 1 mL 5% SRBC antigen or 0.1 mL undiluted BA at 4 and 6 wk of age; blood samples were collected at 0, 4, 7, and 10 d post-immunization. Total, IgG, and IgM titers were measured by agglutination assays. Compared with the RBC2 line, the F line had generally higher total anti-SRBC titers; the differences were significant at 14 d postprimary immunization (PPI) (females); at 10 d postsecondary immunization (PSI) (males); and 4, 7, and 10 d PSI (females) (P < or = 0.05). The F line also had higher IgM titers at 14 d PPI (females) and at 10 d PSI (males) (P < or = 0.05). For IgG titers, a line difference was evident in females at 4 and 10 d PSI (P < or = 0.05); the F line had higher titers than did the RBC2 line. For the antibody response to BA in males, the F line had lower total and IgM titers at 10 d PPI (P < 0.05) than did the RBC2 line. No significant line differences in response to the BA were found in total and IgM titers in female turkeys or in IgG titers in both sexes at any time. These results suggest that selection for fast growth rate of turkeys might have resulted in changes in humoral immunity to the SRBC antigen and BA.

Vitamin E and immune responses of broiler pureline chickens

Immunological responses of cockerels fed diets containing either 10 or 300 mg/kg of vitamin E were measured in three commercial broiler nuclear lines designated as A, B, and C. All cockerels were fed the 10 mg/kg diet to 91 d of age, at which time half were continued on that diet and the other half were fed a diet supplemented to contain 300 mg/kg of vitamin E. Sixteen days after feeding the diets, cutaneous basophil hypersensitivity (CBH), which is an in vivo, cell-mediated immune response, was determined as the increase in toe-web skin thickness 24 h after an injection with phytohemagglutinin-P (PHA-P). Twenty-two days after feeding the diets, heterophils and lymphocytes were enumerated. At this time cockerels were also inoculated intravenously with 0.1 mL of 0.25% SRBC. The injection with SRBC was repeated 27 d later. Six and 20 d after each injection, antibody titers were determined. Mercaptoethanol-resistant (IgG) and mercaptoethanol-sensitive (IgM) antibodies were also measured in the secondary titers. The ratio of heterophils to lymphocytes increased, and CBH response was depressed by feeding the higher vitamin E diet. For cockerels of Lines A and B, the higher level of vitamin E maintained primary and secondary SRBC antibody levels, whereas for Line C, levels were depressed. The effect of the higher vitamin E diet on IgG and IgM was also stock-dependent. The enhanced heterophil:lymphocyte ratio from feeding vitamin E suggests an improved phagocytic ability of the immune system. Relative asymmetries for toe-web skin thickness and shank length were similar for the three lines.

Immune competence, resistance to Escherichia coli and growth in male broiler parent chicks fed different levels of crude protein

Immune competence, resistance to Escherichia coli and growth were measured in female chicks of broiler male parent lines from four different commercial sources. These chicks were fed with three levels of dietary crude protein (CP) from day-old. The protein contents in the diets were 18%, 20.5% and 23%; these diets are referred to as the low-, medium- and high-protein diets, respectively. There was a significant genotype by dietary protein interaction for body weight at 35 days of age but not at 14 or 28 days of age. At 14 days of age, the chicks fed on the high-protein diet weighed significantly more than those fed on the low-protein diet, but there were no differences between the chicks fed on the medium-and low-protein diets. The influence of CP content on body weight had disappeared by 28 days of age. There were significant differences between the genotypes-in antibody production in response to sheep red blood cell (SRBC) inoculation, but no such differences were observed between the chicks fed the different levels of dietary protein. Chicks fed on the high-protein diet had lower lesion scores following E. coli inoculation than those fed on the low-protein diet. There were also significant differences in lesion scores among the genotypes. Genotypes with heavier body weights had significantly higher lesion scores and lower antibody titres than those with less body weight. Also, genotypes of lower body weight had a greater cutaneous basophilic hypersensitivity response to phytohaemaglutinin-P inoculation, and a better humoral response against SRBC and a lower heterophil to lymphocyte ratio.

Influence of body weight restriction in a body-weight-selected line of turkeys on response to challenge with Pasteurella multocida

Previous research has shown that a line (F) of turkeys selected long-term for increased 16-wk BW was more susceptible to challenge with washed Pasteurella multocida (PM) than a randombred control line (RBC2), the base population of the F line. Published research indicated that the mortality of the F line following challenge with PM was similar to that of two commercial sire lines. The purpose of the present study was to determine the influence of reducing BW of the F line to that of the RBC2 line by nutrient restriction on resistance to PM. Four challenge trials were conducted over a 2-yr period. The BW of a group of F line birds was restricted to that of the RBC2 line by limiting access to feed from 1 to 6 wk of age. The F line restricted birds and full-fed RBC2 and F line birds were challenged with a field isolate of washed PM (1.2x10(7) organisms/bird of capsular serogroup A and somatic serotype 3, 4) at 6 wk of age. Birds were checked twice daily for 14 d. Resistance to PM was measured by days to death of those that died and percentage mortality. The BW of the restricted group of the F line did not differ from full-fed RBC2 birds for males or females. In males, the restricted F line birds had similar mortality (48.0%) to the full-fed RBC2 line birds (44.3%), and the mortalities in both groups were significantly lower than that observed for the full-fed F line birds (81.3%) following challenge with PM. The mortality following challenge in females did not differ significantly among groups, even though mortality of the full-fed F line birds (64.1%) and restricted F line birds (63.3%) was more than 9% higher than that (54.2%) observed for the full-fed RBC2 line birds. Days to death was not a sensitive indicator of resistance to PM, as no differences among the three groups of birds were observed for either sex.

Kinetics of antibody responses in hens from chicken lines divergently selected for response to sheep red blood cells

Changes in antibody titers to SRBC were monitored for 180 d after inoculation in hens from two lines divergently selected for 24 generations for high (HAS) or low (LAS) antibody response to SRBC. The HAS hens not only had a higher peak of antibody response (12.9 vs 9.4), but also showed greater persistence in maintaining antibody levels than LAS hens. As a result, HAS hens exhibited higher antibody titers for the 180-d assay period than LAS hens. Antibodies to SRBC were detected in all day-old chicks hatched from HAS eggs collected 10 to 14 d after inoculation as well as 92 to 119 d after inoculation. Only a portion (20 to 75%) of progeny for LAS hens had detectable levels of antibody during the same periods. Among responders, antibody titers were higher for HAS than for LAS progeny. There was a positive correlation among antibody titers taken at different times after the inoculation with SRBC.

Neural sites and pathways regulating food intake in birds: a comparative analysis to mammalian systems

The paper reviews hypotheses explaining the regulation of food intake in mammals that have addressed specific anatomical structures in the brain. An hypothesis, poikilostasis, is introduced to describe multiple, homeostatic states whereby the regulation of metabolism and feeding occur in birds. Examples are given for both wild and domestic avian species, illustrating dynamic shifts in homeostasis responsible for the changes in body weights that are seen during the course of an annual cycle or by a particular strain of bird. The following neural structures are reviewed as each has been shown to affect food intake in birds or in mammals: ventromedial hypothalamic nucleus (n.), lateral hypothalamic area, paraventricular hypothalamic n., n. tractus solitarius and area postrema, amygdala, parabrachial n., arcuate n. and bed n. of the stria terminalis. Two neural pathways are described which have been proposed to regulate feeding. The trigeminal sensorimotor pathway is the most complete neural pathway characterized for this behavior and encompasses the mechanics of pecking, grasping and mandibulating food particles from the tip of the bill to the back of the buccal cavity. A second pathway, the visceral forebrain system (VFS), affects feeding by regulating metabolism and the balance of the autonomic nervous system. Wild, migratory birds are shown to exhibit marked changes in body weight which are hypothesized to occur due to shifts in balance between the sympathetic and parasympathetic nervous systems. Domestic avian species, selected for a rapid growth rate, are shown to display a dominance of the parasympathetic nervous system. The VFS is the neural system proposed to effect poikilostasis by altering the steady state of the autonomic nervous system in aves and perhaps is applicable to other classes of vertebrates as well.

Antibody responses and body weights of chicken lines selected for high and low humoral responsiveness to sheep red blood cells. 1. Effect of Escherichia coli lipopolysaccharide

Antibody (Ab) responses to i.m. administered SRBC and BSA, and i.p. administered Escherichia coli lipopolysaccharide (LPS), and BW at various times after treatment, were measured in chicken lines divergently selected for high (H) and low (L) Ab responses to SRBC, and in a randombred control line (C). The Ab responses to SRBC and BSA, but not LPS, were significantly affected by line by treatment interactions. Levels of antibodies to SRBC and BSA were higher in the H line than in either the C or L line (P < 0.05). Administration of LPS did not affect Ab responses to SRBC, but Ab responses to BSA were decreased in birds that received BSA and LPS simultaneously. Body weights of C and L lines were significantly higher than BW of H line birds at all times. Lipopolysaccharide injection induced an acute, but transient reduction of BW gain, which was not affected by line. Antibody responses to SRBC and BSA were negatively correlated with BW. During the experimental period, however, percentage BW gain and humoral responsiveness were positively correlated. A higher percentage BW gain growth was seen in H line birds at the end of the experimental period. The present results confirm the hypothesized acute cachectin nature of LPS, but the relationship between live BW (gain) and immune responsiveness in chickens remains to be further clarified.

Genetic studies on primary antibody response to sheep erythrocytes in guinea fowl

1. The primary antibody response to sheep erythrocytes was determined by haemagglutination test in guinea fowl. The effects of various genetic and non-genetic factors on immune response to sheep RBCs in guinea fowl were also estimated. 2. The immune response to sheep RBCs was normally distributed in guinea fowl with mean titre at 1.534 +/- 0.014. 3. In guinea fowl, effects on titre values of sire and variety (feather colour) were significant whereas sex and sex x variety interaction effects were non-significant. 4. The estimate of heritability for immune response to sheep RBCs in guinea fowl was 0.35 +/- 0.17.

Dietary effects on immune response of fast-growing chicks to inoculation of sheep erythrocytes and Escherichia coli

Responses to SRBC and Escherichia coli inoculations were measured during the early posthatch period in broiler cockerels fed diets differing in nutrient density. Diet A consisted of 20% protein and 2,685 kcal ME/kg and Diet B consisted of 24% protein and 3,146 kcal ME/kg. There was no effect of diet on antibody response of chicks inoculated at 10 d of age with 0.25, 2.50, 5.00, or 25.00% suspensions of SRBC. A significantly larger proportion of chicks, however, produced antibody at the 25.00% than at the 0.25% dosage of SRBC. When inoculated at 15 d of age with 10(-6), 10(-4), or 10(-2) dosage of E. coli, there were no significant diet by dosage interactions for lesion scores, or relative change in BW 24, 48, and 120 h after inoculation. There were differences among E. coli dosages for severity of lesions and mortality, with rankings being 10(-2) > 10(-4) > 10(-6). Lesion scores and mortality were higher for the chicks fed Diet B than those fed Diet A. Also, deleterious effects of E. coli on BW 24, 48, and 120 h after inoculation were greater for chicks fed Diet B than for chicks fed Diet A. Responses to inoculations of SRBC and E. coli of broilers fed a diet with a lower nutrient density were equal or superior to those of broilers fed a diet with a higher nutrient density.

Long-term divergent selection for eight-week body weight in white Plymouth rock chickens

This paper provides an overview of results from a long-term (38 generations) selection experiment. Lines were developed from individual phenotypic selection for high or low body weight at 8 wk of age. Included are data for the selected lines, sublines in which selection was relaxed, crosses of the selected lines, and sublines in which the sex-linked dw gene was introduced. Periodically (and in some cases every generation) data were obtained for unselected traits. These unselected traits included feed consumption and intake behavior, reproduction, allomorphic relationships, and metabolic, immunological, endocrine, and molecular factors. These responses have been integrated into a resource allocation paradigm.

Feeding regimen by sire family interactions on growth, immunocompetence, and disease resistance in chickens

Progeny from matings of 12 sires from a White Plymouth Rock line selected for high juvenile BW and 96 dams from a White Leghorn line selected for low antibody production to SRBC were reared under alternate-day (AD) or ad libitum (AL) feeding regimens. Within a feeding regimen males were heavier than females, and within a sex, chicks fed AL were heavier than those fed AD. Feeding regimen by sire family interactions were significant for BW at 21 d of age for both male and female progeny. The interaction was due to differences among sires in the magnitude of the AD: AL relationship. Product moment correlation coefficients between feeding regimens for male and female progeny of sire families for 21-d BW were essentially zero, which was consistent with the sire family by feeding regimen interactions observed at this age. At 41 d of age, relative to BW, weights of empty esophagus plus crop and of crop contents were greater for AD than AL chicks. There were differences among sire families for crop content and breast weights relative to BW. Lesion scores to Escherichia coli challenge were lower and antibody titers to SRBC antigen were higher in AD than in AL chicks. Sire families differed in antibody titers to SRBC antigen. Feeding regimen by sire family interactions were significant for percentage change in BW 144 h after E. coli challenge and lesion scores were greater for AL than AD chicks.

Growth related traits in body weight selected lines and their crosses reared under different nutritional regimens

1. Four populations--two that had undergone 37 generations of selection for high (HH) and low (LL) body weight, and reciprocal crosses between them (HL and LH) were fed two diets differing in protein and energy. Diet A, under which selection had been made, contained 200 g protein and 11.23 MJ/kg. Diet E contained 240 g protein and 13.16 MJ/kg. 2. Body weight and feed efficiency were measured weekly from hatch to 56 d of age at which time oesophagus, abdominal fat pad, heart, liver and lungs were removed and weighed. At 35 d of age chicks were inoculated with sheep erythrocytes (SRBC) and antibody titre was measured 6 d later. 3. Chicks fed diet E were heavier than those fed diet A. HH chicks were heavier than LL chicks with HL and LH chicks intermediate to the parental lines. LH chicks were heavier than HL ones reflecting large maternal effects. 4. Food efficiencies among stocks and diets were consistent with those for body weight, with HH > LH > HL > LL and E > A. Relative differences between diets were similar across ages and heterosis for food efficiency was about 15%. 5. Relative to body weight, oesophagus and liver weights were heavier in chickens fed diet A than fed diet E. The pattern reversed for abdominal fat pad. 6. Antibody to SRBC antigen was greater in the crosses than in line HH and in cross HL than line LL, with heterosis of 70%.

A comparison of the immune performance of a 1991 commercial broiler with a 1957 randombred strain when fed "typical" 1957 and 1991 broiler diets

The general objective of the present study was to assess the contribution that changes in genetic selection and dietary regimen have made on the immune performance of broilers. Chicks were hatched from 1991 and 1957 strains and placed on diets thought to be typical of those fed during 1957 and 1991. Immune responses were measured as total, IgM, and IgG antibody production, macrophage, and natural killer (NK) cell functions. Significant differences were observed between strains in antibody production. For example, 1957 males fed 1957 diets had the highest total (P < .0001), IgM (P < .0016), and IgG (P < .015) anti-sheep red blood cell antibodies as compared with all other strain-diet-sex groups. Both strains behaved similarly in terms of inflammatory macrophage recruitment, substrate adherence potential, and in the phagocytosis of sheep red blood cells. A greater percentage of the 1991 strain birds exhibited NK cell activity than all other groups. These studies suggest that genetic selection towards enhanced performance traits has negatively influenced the adaptive arm of the immune system (antibody production) with little or no effect on the nonadaptive components (macrophage and NK functions).