Economic effects of clinical chicken anemia agent infection on profitable broiler production.

An outbreak of anemia dermatitis syndrome caused by chicken anemia agent (CAA) occurred in 15 broiler flocks. An average of 29% of chickens in these flocks were derived from a common breeder flock. The breeder flock had no antibody to CAA at 20 weeks of age but had seroconverted by 31 weeks. Diseased broiler flocks were derived from eggs laid by the breeder flock between 25 and 30 weeks of age. CAA infection in the breeder flock was subclinical, with no apparent effects on mortality or performance. A strategic program of therapeutic and/or prophylactic antibiotic therapy was begun in affected broiler flocks as soon as the disease was diagnosed. Nevertheless, when the cost of therapy was taken into account, affected broiler flocks had a net income 17.3% to 19.6% lower than normal flocks. Average bird weights were 3.3% to 3.5% lower in affected flocks than in unaffected flocks, and affected flocks had a significantly greater proportion of lighter birds. Average mortality in affected flocks was 2.0% to 2.3% higher than in normal flocks, with peak mortality occurring in the third week of life. There was no apparent effect on feed-conversion ratio.     

Campylobacter spp. in conventional broiler flocks in Northern Ireland: epidemiology and risk factors

Risk factors for Campylobacter infection in conventional broiler flocks in the time period up to the first removal of birds to slaughter were investigated over a maximum of five consecutive production cycles in a cohort of 88 broiler farms in Northern Ireland. Samples for Campylobacter culture, which consisted of 14 cloacal swabs per flock, were collected from one house on each farm prior to the first depopulation of birds. In total 388 flocks were sampled, of which 163 tested positive for Campylobacter spp. (42.0%; 95% CI 35.1–48.9%).

Data on farm and flock variables were obtained from questionnaires and random-effects logistic regression modelling used to investigate the association between these and the Campylobacter status of flocks. Six variables, all of which were significant at p < 0.05, were included in the final multivariable model. These included a combined variable on the presence of rodents on farms, which showed an increased odds of infection in flocks where the farmer reported having observed rodents during the production cycle (OR = 2.1) and/or where rodent droppings were observed at the sampling visit (OR = 2.9). Other variables that were significantly associated with an increased odds of infection included the age of the birds at sampling (odds ratio for its linear effect = 1.16 for each day of increase in age), season (summer versus other seasons OR = 2.0), farms with three or more broiler houses (OR = 2.9 compared to those with one house), the frequency of footbath disinfectant changes (OR = 2.5 for once weekly and OR = 4.0 for less than once weekly compared to twice weekly changes) and a categorical variable on the standard of tidiness and cleanliness of the broiler house ante-room (OR = 2.0 and OR = 4.9 for flocks from houses with poorer standards). There was no significant evidence of direct carry-over of infection from one production cycle to the next, neither was there evidence of other farm species acting as a source of infection.     

Reduced incidence of Clostridium perfringens-associated lesions and improved performance in broiler chickens treated with normal intestinal bacteria from adult fowl

The dosing of young chicks with cultures of normal gut flora has been termed "competitive exclusion" (CE). This study was undertaken to examine, under field conditions, the effect of CE treatment on counts of intestinal Clostridium perfringens (CP) and on the occurrence of CP-associated disease in broiler chickens. A farm having recurrent CP-associated health problems was selected as study site. The study comprised four broiler houses, with one treated and one untreated flock per house. Treated birds were sprayed with the CE product Broilact upon arrival at the farm. All flocks were offered feed containing the ionophorous anticoccidial agent narasin. The feed did not contain growth promoters. Treatment was associated with positive but statistically nonsignificant effects on gut health. Delayed intestinal proliferation of CP and delayed appearance of CP-associated gut lesions were found in CE-treated flocks. This delay was associated with improved production performance at slaughter.     

Prevalence of antibody to chicken anaemia virus (CAV) in Swedish chicken breeding flocks correlated to outbreaks of blue wing disease (BWD) in their progeny

A serological survey for antibody to Chicken Anaemia Virus (CAV) was performed on broiler breeders as well as layer breeding birds in Sweden at the end of their rearing period. Grandparents (GP) of both types leaving quarantine were in 21 out of 26 cases free from antibody to CAV, but often became infected soon thereafter. A total of 10 outbreaks of blue wing disease (BWD) in 3 series were recorded in the broiler and layer parent generation, all of which were progeny of 3 late seroconverting GP-flocks. All but one of 22 layer parent flocks had been infected and had seroconverted during the rearing period. Subsequently BWD was not recorded from commercial layers. Broiler parent flocks were more protected from CAV infection during rearing. Eighteen out of 94 broiler parent flocks had not developed antibody to CAV before coming into lay. Outbreaks of BWD were reported in progeny flocks from all these broiler breeders, with the exception of those that had been vaccinated. Good hygienic routines along with isolation of the birds delayed the seroconversion to CAV in broiler breeders and vaccination of these breeders protected their progeny from outbreaks of BWD. Broiler flocks in houses where BWD had occurred recently had always antibodies to CAV at slaughter. It was possible to eradicate the infection from the house and prevent the infection between flocks by proper cleaning and disinfection of the broiler houses.     

National surveillance of Campylobacter in broilers at slaughter in Denmark in 1998

A surveillance study for thermophilic Campylobacter spp. in broiler flocks was carried out for the year 1998 in Denmark. The study included examinations of 4286 broiler flocks comprising samples from 57,000 birds. Overall, a flock prevalence of 46.0% was recorded. The species distribution was Campylobacter jejuni 86%, Campylobacter coli 11%, Campylobacter lari 1%, other not further diagnosed species 2%. The prevalence was significantly higher in the period from June to October (3.2 < odds ratio [OR] <1.8, P < 0.0002) and was significantly associated with abattoir (OR < 2.8, P < 0.0001) and the length of the period the broiler houses were left empty between flocks (download period; 6 days or more) (OR = 1.6, P < 0.0198). No association between Campylobacter colonization and the age at slaughter was found. Separating the flocks into batches for slaughter elevated the flock prevalence from 0.41 after the first batch had been slaughtered to 0.46 after all batches had been slaughtered.     

A study of the epidemiology of infectious bursal disease in poultry in Queensland, 1976–1979

The epidemiology of infectious bursal disease (IBD) was studied by serology and sometimes by visual examination of the bursa of Fabricius in poultry flocks in Queensland during 1976–1979.
Ten flocks, each of approximately 30,000 meat breeding chickens, were surveyed. All chickens had maternally-derived antibody against IBD virus (IBDV) at hatching and active antibody was not detected while the chickens were brooded on rearing farms. When distributed to breeding farms, 7 of the flocks developed antibody when 11 to 25 weeks of age. The remaining 3 flocks were vaccinated by infection of 10% of the birds and within 4 weeks more than 80% of the chickens had developed precipitating antibody to IBDV.
Blood samples of 20 to 30 broiler chickens were collected at slaughter (7 to 9 weeks of age) from each of 312 broiler flocks raised on 37 contract farms. While the samples from 21 flocks were without detectable antibody to IBDV, all serum samples for 263 flocks contained antibody. The ratio of bursal weight to bodyweight was significantly lower in birds from 144 flocks having antibody to IBDV than in birds from 10 flocks that were without detectable antibody. In sequential studies, IBDV antibody became demonstrable in 27 of 30 flocks when the chickens were one to 6 weeks of age and was accompanied by bursal atrophy.
Serological investigation of 4 flocks of layer breeding chickens on a multi-age farm at approximately monthly intervals resulted in antibody to IBDV being detected at every examination.
Serological tests and bursal examinations were carried out weekly in 2 flocks each of 4000 layer chickens between one and 20 weeks of age. Serum antibody developed in one flock at 4 weeks of age and in the other at 17 weeks of age. In both flocks, bursal atrophy occurred concurrently with the development of antibody.     

Effect of diets containing potato protein or soya bean meal on the incidence of spontaneously-occurring subclinical necrotic enteritis and the physiological response in broiler chickens

1. An experiment was conducted to compare and explain the incidence of spontaneously occurring subclinical necrotic enteritis in broiler chickens that were fed on two practical broiler diets that differed in the major protein concentrates (soya bean meal or potato protein concentrates) and examine the relationships between the severity of the disease and the growth performance and physiological responses of the chickens. 2. A total of 840, 20-d-old birds were randomly allocated to 12 pens. Two maize-based nutritionally complete diets that either contained some potato protein or soya bean meal as the major protein supplement were fed for 16 d. Twelve birds were randomly sampled from each pen at the end of the feeding period and their blood sampled and intestinal tracts and livers dissected. 3. The birds fed on the potato protein diet had a significantly 7·7% lower feed intake and a significantly 7·8% lower growth rate compared with the birds fed on the soya-based diet. There were no significant differences in feed conversion efficiency or mortality. There were no differences in the determined apparent metabolisable energy concentrations, however, the apparent dry matter digestibility of the potato protein diet was significantly higher than that of the soya based diet and the apparent crude protein digestibility of the potato protein diet was significantly lower. 4. A significantly higher alpha toxin antibody titre was found in the birds fed on the potato protein diet compared with those fed on the soya protein diet. There was a significantly increased incidence of hepatic lesions in the birds fed on the potato protein diet compared with the birds fed on the soya diet. The mean incidence of intestinal necroses tended to be greater in the birds fed on the potato protein diet (23·6%) compared with the birds fed on the soya-based diet (15·3%). 5. There was a significant linear relationship between ileal digesta sialic acid concentration and serum alpha toxin antibodies, although there were a considerable number of outliers to this relationship. Measurement of sialic acid concentration may be a useful variable to indicate the severity of necrotic enteritis in broiler flocks.     

An economic analysis of the impact of subclinical (mild) necrotic enteritis in broiler chickens

Costs to broiler producers associated with subclinical (mild) necrotic enteritis (SNE) were estimated using published information on impacts on body weight and feed conversion rate (FCR) associated with SNE and costs and revenues associated with broiler production. Estimates were expressed in U.S. dollars from the perspective of poultry producers. SNE was estimated to result in a 12% reduction in body weight and a 10.9% increase in FCR compared with healthy birds. For the purposes of this analysis, we considered scenarios involving hypothetical flocks of 20,000 birds raised to final body weights ranging from 4.63 to 7.94 lb. The incidence of SNE was assumed to occur at 20% based on the literature. For flocks raised for the length of time required to reach these target weights, SNE resulted in a loss to producers ranging from US$878.19 to US$1480.52 per flock. When feed costs required to obtain SNE flocks having a total live body weight equal to equivalent healthy flocks at market age were calculated, the increased cost to producers ranged from US$370.49 to US$739.38 per flock. SNE has the potential to cause a significant negative economic impact in broiler flocks. Strategies to reduce the incidence of SNE may help to increase the profitability of broiler production.     

Subclinical infectious bursal disease in an integrated broiler production operation.

A field study was designed to determine the prevalence of subclinical infectious bursal disease (IBD) in broiler chickens from a commercial poultry company. Bursae of Fabricius (BF) from two vaccinated and three nonvaccinated broiler flocks were evaluated histologically, and antibody profiles of these broiler and matched parent breeder flocks were established. Lesions of IBD, including lymphoid necrosis, stromal edema, and infiltrates of heterophils and macrophages, were first detected in BF at 24 days of age in both vaccinated and nonvaccinated chickens. At 41 days, all BF had lesions characteristic of IBD, including severe lymphoid depletion, proliferation of epithelial cells, and mild fibroplasia. Although mean maternal antibody levels (measured by enzyme-linked immunosorbent assay) in broilers were apparently protective through day 12, IBD antibodies decreased to nonprotective levels (below 1,000) by day 16 or 20. Titers began to increase by day 28 or 32 because of field exposure. Sentinel birds, placed with broiler flocks, also developed IBD antibody titers. Broiler breeders had low and nonuniform antibody titers. Prevalence of field IBD exposure was high, and existing vaccination programs were not effective.     

Rearing conditions and foot-pad dermatitis in Swedish broiler chickens

A method of classification of broiler foot-health status was developed to estimate the prevalence of foot-pad dermatitis in Swedish broilers. Data on foot health were collected from 101 commercial broiler flocks at slaughter. The producers were asked to fill in a questionnaire on rearing conditions and equipment for every flock.

Lesions were commonly observed; only 62% of the birds were classified as being without lesions, 32% had mild lesions only (discoloration, erosions) and 6% had severe lesions (ulcers). Flocks reared in houses equipped with small water cups had significantly (P < 0.05) higher prevalences of foot-pad dermatitis than flocks reared with water nipples. Thick layers of litter, regardless of litter material, also resulted in significantly (P < 0.05) higher prevalences of foot-pad dermatitis than litter layers thinner than 5 cm.     

Subclinical infectious bursal disease in commercial broiler flocks in Saskatchewan.

Five commercial broiler flocks, not vaccinated for infectious bursal disease virus, derived from infectious bursal disease virus-vaccinated breeder flocks were surveyed for evidence of bursal damage and infectious bursal disease virus infection. They were compared with two groups of birds raised in isolation. Serum samples from one day old chicks contained maternal anti-infectious bursal disease virus antibodies which declined to undetectable levels by four weeks of age. Serum antibody levels remained undetectable in both control groups and one commercial flock, whereas four of the five commercial flocks had actively produced anti-infectious bursal disease virus antibodies by slaughter age. The weight of bursae from infectious bursal disease virus-positive flocks declined as compared to controls after four weeks of age. The decline in weight correlated with the appearance of histopathological lesions. Infectious bursal disease virus antigen was demonstrated in selected infected bursae and infectious bursal disease bursae and infectious bursal disease virus was isolated from some of these damaged bursae. Clinical infectious bursal disease was not observed in any of the commercial flocks. The importance of subclinical bursal damage and immunosuppression is discussed.     

Evaluation of serological, histological and immunocytochemical methods for the detection of infectious bursal disease virus infection in broiler flocks in New Zealand

AIMS: TO study and compare three diagnostic methods for the detection of infectious bursal disease virus (IBDV) infection. METHODS: Samples of sera and bursae were collected from two flocks from each of two broiler farms (Farms A and B) in which IBD had occurred or was suspected to have occurred. Sera were tested in ELISA and agar gel precipitation tests for the presence of IBD antibodies. Bursae were examined histologically for evidence of IBD lesions. An immunocytochemical test was developed to detect IBDV antigens in sections of bursa. RESULTS: Bursae from serologically negative, 45-day-old birds from Farm A, Flock 1 and from serologically positive 49-day-old birds from Farm B, Flock 1 had histological and immunocytochemical evidence of IBDV infection. Birds from Farm A, Flock 2, sampled 12 months after the sampling of Flock 1, and specific-pathogen-free birds, showed no evidence of IBDV infection by any of the three diagnostic methods. Birds from Farm B, Flock 2, sampled on four occasions, were positive for IBD at 20 days of age by histology and immunocytochemistry, but did not seroconvert until 42 days of age. CONCLUSIONS: Serological testing is not a reliable method for the detection of IBDV infection in New Zealand broiler flocks because antibodies may not have developed to detectable levels by the time of slaughter. Histological examination of bursae allowed the demonstration of IBD-like lesions, but these need to be differentiated from those caused by other agents. The immunocytochemistry test was able to detect early IBDV infection. It provided a rapid, definitive diagnosis and may be useful in control programmes. The results from Farm A demonstrate that strict biosecurity measures can be successful in the eradication of IBDV.     

The avian major histocompatibility complex influences bacterial skeletal disease in broiler breeder chickens

This study evaluated bacterial skeletal disease in conjunction with the major histocompatibility complex (MHC) in a genetically pure line of broiler breeder chickens. Chickens from six broiler breeder flocks were examined for skeletal lesions, bacterial pathogens, and MHC genotype. During a 10-week period, eighty-eight, 9- to 21-week-old lame chickens and 34 normal, age-matched controls were selected. Tenosynovitis, arthritis, and femoral or tibiotarsal (or both) osteomyelitis occurred in 86 of 88 (97.7%) lame chickens. Ninety-five bacterial isolates were obtained from 83 of 88 (94.3%) lame birds and 4 of 34 (11.8%) controls. Staphylococcus spp. was isolated from 72.6% of the skeletal lesions, predominantly Staphylococcus aureus (38.9%). MHC B complex genotypes were determined by hemagglutination for 88 lame birds, 34 controls, and 200 randomly selected birds from each of the six flocks (1,200 total). Combined chi-square analysis revealed that the homozygous MHC genotypes B(A4/A4) (chi(2) = 14.54, P = 0.0063) and B(A12/A12) (chi(2) = 42.77, P = 0.0001) were overrepresented in the sample of symptomatic birds compared with random samples from the same flocks. The homozygous A4 and A12 MHC genotypes influenced flock chi-square values more than the corresponding heterozygotes. An MHC B complex influence on bacterial skeletal disease was apparent in this line of broiler breeders.     

Prevalence of antibodies against Ornithobacterium rhinotracheale in broilers and breeders in Southern Brazil

In this investigation, we determined the prevalence of the Ornithobacerium rhinotracheale (ORT) infection in broilers and broiler breeders in southern Brazil. We also correlated the presence of antibodies in broilers with performance. Sera from 1550 broilers from 50 flocks were collected during the slaughter time in nine companies with federal veterinary inspection of the state of Rio Grande do Sul. Sera from 480 meat-type breeders of 40 flocks from 14 companies in southern Brazil were also analyzed by enzyme-linked immunosorbent assay, and the prevalence of antibodies was determined. The prevalence of ORT antibodies in broiler flocks was 63.83%, but in each individual flock only 6.52% of the birds were positive. The prevalence in broiler breeder flocks was 100.00%, and in each individual flock 94.62% of the birds were positive. There was a positive correlation between the presence of antibodies to ORT and decreased body weight in broilers. There was no significant correlation between presence of antibodies to ORT and age, lineage, efficiency index, feed conversion, and mortality. There was a positive correlation between the presence of respiratory signs and antibodies to ORT, although the reverse correlation was not significant. These results confirm that ORT is present and widespread in broilers and broiler breeders in southern Brazil.     

Flock data reported from a poultry slaughter house (broilers)]

Six broiler flocks have been compared with regard to the occurrence of attributes according to an examination protocol. Approved birds were scrutinized per random sample, condemned birds altogether. Parameters of examination were body weight occurring attributes (computed single and cumulated) count of dead and condemned birds in fattening period, transport and on slaughter line as well. Each flock was conspicuous in one or another respect. The graduation of the flocks was possible using the factors losses in the fattening period count of condemnation losses in the total production line coefficient of variation of weights attributes occurring in the meat inspection cumulated count of all attributes leading to condemnation. Results demonstrate, that graduation of different flocks by means of quantitative measurements is possible.     

Field efficacy of different vaccines against infectious bursal disease in broiler flocks

A field study was performed to determine the efficacy of three commercially available vaccines against infectious bursal disease (IBD) in commercial broilers raised in a high IBD virus (IBDV) risk area. Live attenuated intermediate and intermediate plus vaccines were used in four flocks. Birds were vaccinated orally at the estimated vaccination time. Three broiler flocks were vaccinated subcutaneously with a turkey herpesvirus (HVT)-IBD vector vaccine at one day old. Evaluation of the efficacy of different vaccines was focused on humoral immune response, bursa/body weight (B/Bw) ratio, molecular detection of IBDV in ileocaecal tonsils and bursa of Fabricius, and production parameters. The serological results showed that although the uptake of all three vaccine strains was confirmed in the lymphoid organs, no significant antibody response to vaccination was detected in flocks vaccinated with intermediate and intermediate plus vaccines. A significant increase in antibody titres detected in flocks vaccinated with the vector vaccine indicated its ability to induce an immune response in birds with a high level of maternally derived antibodies. Observations obtained in this field trial did not confirm the expected reduction of the B/Bw ratio in flocks vaccinated with less attenuated vaccines. No significant differences were observed between birds vaccinated with the vector vaccine and those immunised with the intermediate plus vaccine. Very virulent IBDV was confirmed in the flock vaccinated with the intermediate vaccine. The infection induced reduced B/Bw and moderate mortality but did not affect the production parameters. Field infection was not detected in broilers vaccinated with the intermediate plus vaccine and the vector vaccine.     

Measurements of footpad dermatitis in broiler chickens at processing plants

A four-point photographic scale was developed to score the severity of lesions of footpad dermatitis (FPD) in broiler chickens. There was a linear relationship between the square root of the relative area of the lesions and their scores, and good agreement between different assessors using the scale. The scale was used to assess samples of 100 birds from each of 190 flocks slaughtered at two uk processing plants in 2002 and 2003; 12 of the flocks (6.3 per cent) had no lesions, but the others had lesions of different prevalences and severity. The maximum proportion of affected birds in a flock was 92 per cent. In the 178 affected flocks, 84.0 per cent of the birds had no lesions and 16.0 per cent had some evidence of FPD. The overall unweighted prevalence of birds with FPD in all 190 flocks sampled was 18.1 per cent; 10.2 per cent had only small lesions, on average equivalent in area to 2.1 per cent of the total area of the foot, 6.2 per cent had lesions on average equivalent to 6.6 per cent of the area of the foot, and 1.7 per cent had lesions on average equivalent to 21.5 per cent of the area of the foot. There were differences between the two plants in the overall prevalence and severity of FPD, but this may have been due to the fact that the plants were sampled at different times of the year.     

A comparison survey of organic and conventional broiler chickens for infectious agents affecting health and food safety

The purpose of the present cross-sectional study was to evaluate the health status of organic broiler chickens and the contamination rate with Salmonella and Campylobacter in organic broiler production in Belgium. The broilers were screened for antibodies against routinely monitored poultry diseases at 1 day old and at slaughter. Fecal examination for the presence of worm eggs was done at slaughter. Bacteriological examination for the detection of Salmonella and Campylobacter was performed at day 1, week 2, week 4, week 7, week 10, and slaughter. Conventional broilers of the same poultry integration and reared in the same geographic area were also screened and served as reference. Serologic data indicated lower antibody titers against infectious bronchitis and Newcastle disease in organic flocks. No significant differences could be found in prevalence of Salmonella between organic and conventional broilers at slaughter. In contrast, Campylobacter infections at slaughter were significantly higher in organic flocks. Organic flocks most probably become infected with Campylobacter between week 7 and week 10. Worm eggs were found in neither the organic flocks nor the conventional flocks. In conclusion, there are indications that the respiratory health status is better in organic broilers but that organic flocks are more often infected with Campylobacter than are conventional flocks.     

发酵黄芪对肉鸡生长性能、抗氧化功能的影响

试验旨在研究黄芪发酵前后对肉鸡生长性能、抗氧化功能的影响。将210只1日龄AA肉鸡随机分为7组,每组3个重复,每个重复10只。A组为对照组,饲喂基础日粮;B、C、D、E、F、G组分别在基础日粮中添加0.2%黄芪、0.5%黄芪、0.8%黄芪、0.2%发酵黄芪、0.5%发酵黄芪、0.8%发酵黄芪,添加量以质量百分比计。试验期为42 d。分别于第21、42天测定肉鸡生长指标、抗氧化指标。结果表明,在第21天,发酵黄芪组平均日采食量均显著高于黄芪组（P < 0.05）,黄芪组料重比显著低于对照组和发酵黄芪组（P < 0.05）;E组血清过氧化氢酶（CAT）含量显著高于A、B组（P < 0.05）,血清谷胱甘肽过氧化物酶（GSH-Px）活性显著高于与A组（P < 0.05）。在第42天,发酵黄芪组平均日增重均较高,料重比显著低于A、B组（P < 0.05）;试验组GSH-Px活性均显著高于A组（P < 0.05）,发酵黄芪组与黄芪组相比差异不显著（P > 0.05）,发酵黄芪组血清中超氧化物歧化酶（T-SOD）活性均高于黄芪组,且与B和C组差异显著（P < 0.05）。综上所述,在肉鸡日粮中添加一定量发酵黄芪能显著提高平均日增重,降低料肉比,且可通过提高血清中GSH-Px和T-SOD活性来提高其抗氧化能力;发酵黄芪的作用效果优于黄芪,最适宜添加量为0.5%。     

Epidemiology and significance of chicken infectious anemia virus infections in broilers and broiler parents under nonvaccinated European circumstances

A serologic survey in unvaccinated broiler parent and broiler progeny flocks demonstrated seroconversion against chicken infecrious anemia virus (CIAV) in all parent flocks before or around point of lay and in 38% of the broiler flocks examined at slaughter age. The presence of CIAV antibodies at slaughter of broilers was positively correlated with slaughterhouse condemnation rates. Results indicate that CIAV infections are highly prevalent in both broiler parent and broiler flocks and that CIAV infections in broilers are associated with increased slaughterhouse condemnation.