Detection of chicken anemia virus in the gonads and in the progeny of broiler breeder hens with high neutralizing antibody titers

Previous evidence for the presence of chicken anemia virus (CAV) in the gonads of immune specific-pathogen-free chickens raised the question whether this occurs also in commercial breeders. The presence of CAV was investigated by nested PCR in the gonads and spleens of hens from two 55- and 59-week-old, CAV-vaccinated (flocks 2 and 3), and two 48- and 31-week-old non-vaccinated broiler breeder flocks (flocks 1 and 4). In addition, lymphoid tissues of 20-day-old embryos from these hens were also investigated for the presence of CAV. CAV was detected in the gonads and of 5/6 and 11/22 of the vaccinated hens and in some hens also in the spleen alone. Embryos from 7/8 and 5/18 of these hens were positive. In the non-vaccinated flocks, CAV was detected in the gonads of 11/34 and 10/10 hens in flocks 1 and 4, respectively. In addition, 11 birds in flock 1 had positive spleens. CAV DNA was detected in 3/11 and 2/10 of their embryos. CAV-positive gonads and embryos were detected in samples from hens with moderate as well as high VN antibody titers. Vaccinated chickens positive for CAV in the gonads and in their embryos had VN titers ranging from >1:512 to <1:2048. In non-vaccinated chickens, the VN titers of CAV positive chickens ranged from 1:128 to 1:4096. These results demonstrate that CAV genome can remain present in the gonads of hens in commercial broiler breeder flocks even in the presence of high neutralizing antibody titers that have been associated with protection against CAV vertical transmission. It also suggests that transmission to the progeny may occur irrespectively of the level of the humoral immune response in the hens.     

Antibody responses of hens fed vitamin E and passively acquired antibodies of their chicks

Antibody responses of hens and their progeny were studied in commercial broiler nuclear lines. Starting at 168 days of age, individually housed pullets from lines A and B were fed a 16% crude protein and 2752 kcal metabolizable energy/kg mash diet supplemented with either 10 or 300 IU/kg of vitamin E fed as dl-alpha-tocopherol acetate. Fifty-eight days later (226 days of age), 12 hens per line-vitamin E subclass were inoculated i.v. with 0.1 ml of a 2.5% suspension of sheep red blood cells (SRBC). Plasma antibody titers were measured 6, 20, 40, 54, 70, and 88 days after inoculation. Hens from both lines were artificially mated to males from line C, and progeny from eggs collected 9-15, 25-30, and 65-70 days after inoculation were tested for antibodies to SRBC. Hens were reinoculated i.v. with 0.1 ml of 0.25% SRBC 88 days after the first inoculation, and their antibody levels were measured 3, 6, and 20 days later. Eggs laid 10-13 days after reinoculation were incubated, and antibody titers of chicks were measured at hatch. Antibody response of hens to an initial inoculation of SRBC was line-diet-time after inoculation specific. In line A, titers were greater for hens fed the lower than the higher vitamin E diet, whereas diet had no effect on the antibody levels in line B. Line effects (A > B) were observed on days 6 and 20 after inoculation but not thereafter. After the second inoculation, dietary vitamin E level had no effect on antibody levels of hens within lines, whereas a between-line difference (A > B) was observed for the lower but not the higher level of dietary vitamin E. Although there was no difference between diets for antibody transferred to progeny by line B, there was a difference (lower > higher) for line A. After reinoculation of their dams, antibody titers of chicks from line A, but not line B, reached levels similar to those after the first inoculation. Antibody levels were higher for chicks at hatch than in 16-day embryos or 10 days posthatch. The results of this research suggest genetic variation in response to immune stimulation by dietary vitamin E.     

不同种类多不饱和脂肪酸对产蛋鸡抗体产生和淋巴细胞增殖的影响

选用360只60～70周龄海兰褐蛋鸡,研究不同种类的多不饱和脂肪酸(PUFA)在不同添加水平下对产蛋鸡免疫功能的影响。试验共设10个处理,其中n-3PUFA的来源分别为亚麻籽油和鱼油,在日粮中的添加水平分别为20、40、60和10、30、50g/kg。n-6PUFA的来源为玉米油,在日粮中的添加量为20、40和60g/kg,另设一处理为不添加脂肪酸的对照组。在试验开始后的第5周和第7周分别给每个处理组中的6只鸡注射牛血清白蛋白抗原(BSA)和绵羊红细胞(SRBC),并分别于注射后第6,10,14天和第5,9,13天翅静脉采血,测定BSA抗体效价和SRBC抗体滴度。在试验开始后的第5周和第10周,采血测定外周全血淋巴细胞增殖速度,同时每个处理杀3只鸡,取脾脏制备单核细胞,测定其增殖速度。试验结果表明,日粮中添加PUFA具有提高产蛋鸡一免及二免BSA抗体和SRBC抗体产量的趋势,并呈现剂量依赖性。其中高鱼油添加组在一免10天时能显著(P<0.05)提高SRBC抗体滴度,二免后高鱼油添加组和高亚麻籽油添加组都能够显著(P<0.10)提高SRBC抗体滴度;对于BSA抗体效价,高n-3PUFA添加组都能够显著(P<0.10)提高。产蛋鸡外周全血淋巴细胞和脾脏单核细胞增殖速度在饲喂添加高n-3PUFA日粮后受到明显抑制。鱼油来源的n-3PUFA对产蛋鸡免疫功能影响程度比亚麻籽油的大。     

Serum agglutinin titers against somatic and flagellar antigens of Campylobacter jejuni and isolation of Campylobacter spp in chickens

From June 1983 to June 1984, two hundred twenty-five 3- to 30-month-old chickens (hens) on 10 different farms were examined for Campylobacter spp. Watering trays and fly vectors also were examined for Campylobacter spp on 6 of the 10 farms. Campylobacter jejuni was isolated from fecal specimens from 64 hens (28.4%), C coli was isolated from 6 hens (2.7%), and C laridis was isolated from 9 hens (4%). The isolation rate of C jejuni was 6.7% to 46.7% for 9 of the 10 farms. On 2 farms, agglutinin titers greater than or equal to 1:40 against somatic and flagellar antigen of C jejuni were detected in hens from which the bacteria were isolated. Hens having titers greater than or equal to 1:40 against C jejuni or hens from which C jejuni had been isolated often occupied adjacent pens. Campylobacter jejuni was isolated from a watering tray on 1 farm and from fly vectors on 2 farms.     

Serological detection of experimental Salmonella enteritidis infections in laying hens

The antibody response of laying hens to experimental Salmonella enteritidis infection was evaluated in microagglutination, tube agglutination, and rapid whole-blood plate agglutination assays. Hens of three different ages were infected by either oral inoculation or horizontal contact transmission. Blood was collected at weekly intervals, and the presence of specific antibodies was assessed by reaction with antigens prepared from strains of S. enteritidis and S. pullorum. The sensitivity of detection of infected hens did not vary significantly between the assays, as all three tests effectively identified most exposed hens as seropositive. Within each test, however, variation was observed in the detection sensitivity when different antigens were used. The microagglutination titers of serum samples were determined by serial dilution. Antibody titers peaked at 1 to 2 weeks postinoculation and declined steadily, although most birds were still identified as seropositive at 10 weeks postinoculation. The mean microtest titers obtained with S. enteritidis antigens were higher than with an S. pullorum antigen, indicating greater test sensitivity. However, use of the S. pullorum antigen resulted in fewer false positives when sera from uninfected control hens were tested. The titers of contact-exposed hens peaked later and at lower values than did those of inoculated hens, but these two groups of hens had similar antibody titers after the third week postinoculation.     

Identification and characterization of hens transmitting avian leukosis virus (ALV) to their embryos by ELISAs for detecting infectious ALV, ALV antigens and antibodies to ALV.

A total of 72 White Leghorn grandparent hens was examined by ELISA for avian leukosis virus (ALV), ALV antigens and anti-ALV antibodies to identify and characterize the hens transmitting ALV to their embryos (transmitters) by using fertilized eggs. These hens were divided into 3 groups as no antibody and non-viremic (NANV) (49 hens), antibody-positive and non-viremic (APNV) (21 hens) and no antibody and viremic (NAV) (2 hens) by testing the sera for the presence of ALV and anti-ALV antibody. Egg albumen and embryos were tested for the presence of ALV and ALV antigens. As a result, no ALV was detected in both albumen and embryos in the NANV group. On the other hand, all albumen samples collected repeatedly from 3 hens of the APNV group and 2 hens of the NAV group contained infectious ALV, although the infectivity differed with the individual. Also, these 5 hens produced infected embryos at varying frequencies. However, on AP hen which shed neither ALV nor ALV antigens into the albumen produced an infected embryo at a lower rate. These results indicate that testing for infectious ALV in albumen from a newly laid egg per hen is effective to identify the transmitters to some extent. When virus titers in each of 8 tissue samples from the 6 transmitting hens were determined, the highest virus titers were found in washing from the ampulla of the oviducts in most of the shedders, suggesting that embryo infection is closely correlated with ALV produced at the oviduct, but not with ALV transferred from the other parts of the body.     

Use of an enzyme-linked immunosorbent assay to measure antibody levels in turkey breeder hens, eggs, and progeny following natural infection or immunization with a commercial Bordetella avium bacterin

Twelve large white turkey hens were immunized with a commercially available Bordetella avium bacterin. Hens and eggs were tested using an enzyme-linked immunosorbent assay (ELISA) to determine the response to the bacterin. Three hundred poults were then obtained from two commercial flocks, the hens of one flock having been immunized with the same bacterin used on the group of 12 turkeys. Titers of the poults were monitored for 7 weeks, and poults were challenged by exposure to infected poults at 1, 7, 14, and 21 days post-hatch. Hens produced an antibody response following immunization, with a parallel antibody response being detected in eggs. Maternal antibodies were present in poults from immunized hens. Poult titers declined to near the level of poults from unimmunized hens by 14 days of age. Poults from immunized hens challenged at 1 and 7 days were resistant to development of clinical disease and gross lesions, whereas all poults from unimmunized hens exhibited clinical signs and gross lesions. After 14 days, the resistance of both groups to development of clinical disease, became near equal, neither group being affected as severely as the unimmunized hens challenged at days 1 and 7. Six commercial turkey breeding flocks and their progeny that had not been vaccinated for B. avium and had no history of B. avium infection were evaluated with the B. avium ELISA. There were variations between the flocks, with poult titers reflecting those found in the hens.     

Effects of avian infectious bronchitis virus (Arkansas strain) on vaccinated laying chickens

Twenty-four-week-old white leghorn layers were inoculated subcutaneously with a killed Newcastle-infectious bronchitis (Massachusetts type) virus (MIBV) vaccine. The birds were challenged 194 days later intraocularly with Arkansas strain of infectious bronchitis virus (AIBV). The challenged hens laid significantly (P less than 0.005) fewer eggs than the unchallenged layers, and the eggs laid by the challenged groups weighed significantly less (P less than 0.001) than those laid by the unchallenged groups. Further, the internal quality (Haugh units) and shell quality of eggs laid by the challenged hens were significantly (P less than 0.005) inferior to the quality of eggs from unchallenged hens, and the challenged hens laid more soft-shelled, misshapen, and small-sized eggs than the unchallenged hens. The Arkansas serum hemagglutination-inhibition (AIBV-HI) titers of challenged birds increased continuously through 29 days post-challenge. The MIBV hemagglutination-inhibition (MIBV-HI) titers of killed-MIBV-vaccinated birds decreased during the same period. The study indicates that killed MIBV vaccine offered no protection to birds exposed to AIBV. The same vaccine was quite effective against a homologous (MIBV) virus challenge.     

Replication-competent endogenous avian leukosis virus in commercial lines of meat chickens

Group-specific (gs)-antigen-positive egg albumen in seven commercial lines of meat chickens was found to result from the presence of endogenous avian leukosis virus (ALV); these lines had resisted selection attempts to reduce the shedding rate. In two meat lines, exogenous as well as endogenous ALV contributed to the gs-antigen shedding. All hens that produced gs-antigen-positive albumen transmitted endogenous ALV to a high proportion of their embryos (20 to 100%). Hens shedding gs-antigen to albumen were negative for endogenous ALV in vaginal swabs and had no detectable antibody to subgroup E virus. Chickens hatched from these dams were negative for endogenous ALV in meconia but were viremic at 2 weeks of age. Replication-competent endogenous ALV was almost uniformly expressed in embryos of hens from nine meat lines that were negative for gs-antigen in albumen. Shedding of gs-antigen to albumen was not related to the level of endogenous ALV expression. Embryos from five meat lines tested were resistant to infection with ALV of subgroup E. The level of endogenous gs-antigen in albumen was consistently lower than the level of exogenous gs-antigen.     

Effects of Salmonella enterica subsp. enterica serovar Enteritidis vaccination in layer hens subjected to S. Enteritidis challenge and various feed withdrawal regimens

Levels of Salmonella enterica subsp. enterica serovar Enteritidis infection and serum S. Enteritidis antibodies after experimental S. Enteritidis challenge and feed withdrawal were investigated in S. Enteritidis-vaccinated and unvaccinated hens. The results were used to determine whether formalin-inactivated S. Enteritidis vaccination can protect layer hens from S. Enteritidis challenge during feed withdrawal periods. S. Enteritidis infection rates were evaluated from cloacal swabs, eggs and organs. Serum antibody titers to deflagellated S. Enteritidis whole cells (DEWC) and S. Enteritidis FliC-specific 9-kDa polypeptide (SEp 9) were examined by commercial ELISA kits. Cloacal S. Enteritidis recovery rates were lower in the vaccinated than unvaccinated group. Recovery rates of S. Enteritidis from samples increased after feed withdrawal and decreased after re-introduction of feed. S. Enteritidis counts in cloacal swabs were lower in the vaccinated than in the unvaccinated group (P<0.05). More S. Enteritidis-positive eggs were detected from the unvaccinated group. Before S. Enteritidis challenge, the DEWC ELISA titer of the vaccinated group was higher (P<0.05) than the unvaccinated group; subsequently, the S. Enteritidis DEWC ELISA titers of both groups increased gradually. In contrast, only the vaccinated group elicited high SEp-9 antibody titer during post-challenge and feed withdrawal. Additionally, vaccinated hens yielded negative S. Enteritidis isolation rates from egg contents. There is a correlation between negative S. Enteritidis isolation rates and high SEp 9 titers in vaccinated layer hens challenged with S. Enteritidis and subjected to feed withdrawal regimens. These findings suggest the S. Enteritidis vaccination of pullets may protect against S. Enteritidis infection during forced molting and that SEp 9 titer could be a potential indicator of antibody protection against S. Enteritidis infection. The potential of the SEp 9 peptide as an antigen for S. Enteritidis vaccination in the future is worth noting.     

Effect of nitrofurazone or novobiocin on Salmonella enteritidis cecal colonization and organ invasion in Leghorn hens.

Nitrofurazone (433 mg/liter drinking water) administration to leghorn laying hens for 72 hours with a 48-hour withdrawal period before nitrofurazone-sensitive Salmonella enteritidis challenge resulted in a S. enteritidis culture-positive rate significantly (P less than 0.05) higher than that of unmedicated controls when hens were cultured 6 days following challenge. In a similar experiment, simultaneous nitrofurazone administration and S. enteritidis challenge resulted in no significant differences in S. enteritidis isolation frequency. However, unchallenged nitrofurazone-medicated contact control hens showed a significantly higher S. enteritidis culture-positive rate than the unchallenged unmedicated controls. This increase in apparent S. enteritidis susceptibility was associated with significantly lower cecal propionic acid and fewer anaerobic colony-forming units (CFU). In a third experiment, nitrofurazone treatment had no effect when the antibiotic was withdrawn 72 hours before S. enteritidis challenge. In a subsequent experiment, novobiocin (385 mg/kg) or nitrofurazone (300 mg/kg) was administered to adult hens for 7 days before challenge with nitrofurazone and novobiocin-resistant S. enteritidis. Both nitrofurazone and novobiocin administration resulted in a significantly higher S. enteritidis culture-positive rate than unmedicated controls at end of the experiment 7 days post-challenge. Results indicate that administration of some antibiotics may enhance susceptibility to S. enteritidis in leghorn hens.     

Strain Response of Laying Hens to Varying Dietary Energy Levels With and Without Avizyme Supplementation

The response of 4 strains of laying hens fed diets varying in ME with and without Avizyme 1500 (AVI) supplementation was evaluated in a factorial arrangement study. The strains of laying hens (Hy-Line W-36, Hy-Line Brown, Babcock B300, and Shaver White) were fed 3 diets: moderate ME (2,900 kcal/kg), low ME (2,810 kcal/kg), and low ME with AVI for 28 wk commencing at 22 wk of age. No significant effects of diet, strain, or their interaction on feed intake and BW change were observed. Lack of an effect on feed intake was surprising given the different levels of ME. It is hypothesized that the reduced dietary ME was not low enough to elicit a response. Of course, dietary level of ME did change caloric intake among hens, with hens fed moderate ME consuming more calories than those fed low ME with or without AVI. There was an interesting dietary ME × strain interaction effect on egg production (EP). Babcock B300 hens fed moderate ME and low ME with AVI had greater EP compared with the B300 hens fed low ME, whereas the Shaver White hens had a greater EP when fed a low-ME diet compared with feeding a moderate-ME diet or low-ME diet with AVI. Egg weight and egg mass were significantly affected by strain but not by diet ME. Hy-Line Brown and Babcock B300 hens laid eggs with greater weight and mass in contrast to Hy-Line W-36 or Shaver White. Hy-Line Brown eggs were the largest, whereas Shaver White had greatest egg-specific gravity. Strain significantly affected proportions of albumen vs. yolk in the egg. Across all strains, Hy-Line Brown had more albumen percentage, whereas Hy-Line W-36 had higher wet yolk and yolk solids percentages. The low-ME level fed to laying hens may have been too high to evoke an enzyme response to improve energy utilization by birds. This is important, because to obtain an economic benefit, producers would need to know the proper ME level to feed with the supplemental enzymes.     

Antibody response to and maternal immunity from an experimental psittacine beak and feather disease vaccine.

Adult umbrella cockatoos, Moluccan cockatoos, African grey parrots, and a yellow-headed Amazon parrot were inoculated IM or SC with beta-propiolactone-treated psittacine beak and feather disease (PBFD) virus. Thirty- to 45-day-old African grey parrot, umbrella cockatoo, and sulphur-crested cockatoo chicks also were vaccinated with the same inoculum. The hemagglutination inhibition (HI) and agar-gel diffusion tests were used to assay for post-vaccination development of anti-PBFD virus antibodies. All adult vaccinates seroconverted and had increases in HI and precipitating antibodies. The vaccinated chicks had increased concentrations of HI antibodies, but precipitating antibodies could not be detected. To demonstrate that chicks from vaccinated hens are protected from PBFD virus challenge, 3 African grey parrot chicks and 2 umbrella cockatoo chicks from vaccinated hens and 1 African grey parrot chick and 1 umbrella cockatoo chick from nonvaccinated hens were exposed to purified PBFD virus. Chicks from the vaccinated hens remained clinically normal during the 50-day test period. Chicks from the nonvaccinated hens developed clinical and histologic lesions of PBFD. Infected tissues from these birds were confirmed to contain viral antigen, using immunohistochemical staining techniques. The PBFD virus was recovered from the affected birds. These findings indicate that adult and 30- to 45-day-old psittacine birds will seroconvert following vaccination with beta-propiolactone-treated PBFD virus. Also, hens inoculated with beta-propiolactone-treated PBFD virus produce chicks that are, at least temporarily, resistant to virus challenge.     

Sporadic congenital transmission of avian leukosis virus in hens discharging the virus into the oviducts.

The efficacy of the albumen test for infectious avian leukosis virus (ALV) was examined in detecting congenitally transmitting hens. Seventy-three White Leghorn non-viremic hens with antibody to ALV were used. Eleven of the hens shed infectious ALV into their egg albumen, whereas only 7 of the 11 ALV-positive hens shed ALV antigens. The egg albumen test for infectious ALV was shown to be more effective in detecting the congenitally transmitting hens than that for ALV antigens. Then, twenty of the 62 hens which shed no infectious ALV into the albumen were studied for transmission of ALV to their embryos and for discharging ALV into the oviduct and vagina. Six of the 50 embryos from 4 hens were found to be infected with ALV but all of the 227 embryos from remaining 16 hens were free from the infection. Discharge of the virus into the oviduct and vagina was found both in the 4 transmitting hens and in 6 of the 16 non-transmitting hens. These results suggest that the hens discharging ALV into the oviduct, even though they do not shed ALV into egg albumen, may transmit the virus sporadically to their embryos.     

Diagnostic utility of egg yolk for the detection of avian metapneumovirus antibodies in laying hens

Surveillance and diagnosis of avian metapneumovirus (AMPV) infection typically involve measurement of serum antibodies. In the current study, eggs instead of serum samples were used for the detection of AMPV antibodies in egg-laying chicken hens by enzyme-linked immunosorbent assay (ELISA). AMPV-free commercial layer hens were experimentally challenged with AMPV strain SC1509 through intravenous or oculonasal administration. Antibody levels were determined by ELISA. AMPV antibodies were detected in egg yolks from challenged hens by 7 days postinoculation (dpi), with the peak titer at 16 dpi. Antibody levels in eggs laid at 28 dpi correlated well (r = 0.93) with sera taken 28 dpi from the same hens. In a field trial of the yolk ELISA, six broiler breeder farms were surveyed, and all tested positive for AMPV antibodies in hen eggs, although positivity varied from farm to farm. Abnormal discolored eggs collected from outbreak farms had significantly higher titers of AMPV yolk antibodies than normal eggs from the same farm, unlike clinically healthy farms, where normal and abnormal eggs had similar antibody titers. These results indicate that diagnosis of AMPV infection by yolk ELISA to detect anti-AMPV antibodies may be a suitable alternative to serologic testing.     

母鸡输卵管畸形发生原因的分析

某种鸡场一群艾维茵父母代种鸡中出现“假性母鸡”,剖检发现输卵管畸形。这批种鸡在17日龄时发生过某传染病。进行发病情况调查、对病死雏鸡的剖检和开产期病死母鸡的剖检、病料鸡胚感染和传代试验及新城疫病毒干扰试验。结果,鸡胚感染中第3代出现侏儒胚,干扰组的新城疫血凝价均低于20,对照组新城疫血凝价高于40。综合分析,可以判定该雏鸡在3周龄发生的疾病是鸡传染性支气管炎,以及可以确定该鸡群中不少鸡只出现输卵管畸形是由鸡传染性支气管炎病毒早期感染而引起的。     

Resistance of chickens to Rous sarcoma virus challenge following immunization with a recombinant avian leukosis virus

An attenuated recombinant avian leukosis virus (ALV) produced by recombinant DNA techniques was examined for its ability to provide resistance to Rous sarcoma virus (RSV) challenge. Specific-pathogen-free chicken embryos (18-day incubation) and hatched chicks inoculated with recombinant ALV produced significantly smaller tumors than sham-inoculated controls upon challenge with RSV 2 weeks postinoculation; inoculation with RAV-1 produced similar results. Specific-pathogen-free hens inoculated with recombinant ALV produced viral-protein-specific antibody that was transmitted to 100% of the progeny, as detected by enzyme-linked immunosorbent assay. Progeny of the inoculated hens produced significantly fewer tumors than sham-inoculated controls upon challenge with RSV at hatch, indicating that maternal antibody may be a factor in resistance to tumor development.     

Stress parameters and immune response of layers under different cage floor and density conditions

The aim of the experiment was to investigate the effects of cage floor and cage density on stress parameters of laying hens. A total of 162 brown laying hens (Hyline Brown), aged 34 weeks, were used in the experiment. Compact-type battery cages, with three floors, were used. Hens were allocated as one, three or five hens in each of 18 cages to obtain three different cage density groups of 1968, 656 and 393.8 cm² floor area per hen, respectively. The same number of cages with different cage density were allocated to three different battery floors (first floor=top, second=middle, third=bottom) systematically. Values for body weight, mortality rate, egg weight, egg production, egg quality characteristics, egg yolk cholesterol content, the levels of blood plasma corticosterone, serum glucose, total cholesterol and triglycerides, the ratio of heterophils to lymphocytes (H-L ratio), antibody titers, claw length score, foot health score, plumage score and throat skin injuries were taken as indicators of stress. The values for egg weight (P<0.01) at the first floor were greater than the other floor levels. The group with five hens per cage had significantly lower mean estimates (P<0.01) than other groups with respects to body weight (P<0.001), egg production (P<0.001), egg weight (P<0.001) and plumage score (P<0.01), while significantly higher mean estimates for egg albumen index (P<0.01), Haugh unit (P<0.01), serum glucose (P<0.001), and H-L ratio (P<0.001). Serum cholesterol was higher in cages with one hen than that with five hens, whereas plasma corticosterone was lower. Antibody titers in cages with one hen was similar to that with three or five hens; however, those with three hens had higher titers than those with five hens. Values for egg breaking strength, yolk index, egg cholesterol content, and foot health score were not affected by cage density or floor. The results suggest that the allocation of three hens per cage had no measurable effect on health and welfare.     

Unexpected pattern of antibody response of hens following infectious bursal disease virus vaccine

The antibody titers to infectious bursal disease virus (IBDV) of a group of hens were determined every 2 weeks during the laying period using a kinetic-based enzyme-linked immunosorbent assay (ELISA). When the titers of the flock were regressed against time, the flock titer decayed with statistically significant linearity. However, when the antibody titers of individual hens were measured, their titers regressed on time in a significant quartic curvilinear fashion. Since these hens were not reimmunized, this suggests that a anamnestic response was stimulated from an unknown external source.     

Seroprevalence of antibodies specific for gram-negative core antigens in chickens on the basis of an Escherichia coli J5 enzyme-linked immunosorbent assay

Antibodies directed toward gram-negative core antigens (GNCAs) have been demonstrated in many mammalian species but to date are unexamined in any avian species. An enzyme-linked immunosorbent assay with phenol-killed whole cell Escherichia coli J5 was used to assess the presence of serum antibodies directed toward GNCAs in chickens. The first experiment consisted of collecting blood samples from randomly selected hens at egg laying ranches in northern California. The ages ranged from several days of age to 77 wk of age. Birds were classified into age groups (hatchling [1 day-4 wk], pullet [4-18 wk], pullet cycle [18-60 wk], and postmolt [>60 wk]) and husbandry style for titer comparison. The geometric mean titer (GMT) for all adult hens regardless of age was 2147. The geometric mean titers were 220, 5691, 2304, and 1776 for hatchlings, pullets, pullet cycle hens, and postmolt hens, respectively. The age group titer trends were similar to those of humans rather than those of farm animals in that the highest titers occurred during "adolescence" (pullets) and titers decreased slightly with maturity. The GMTs were 2870 for hens housed intensively and 1872 for those housed extensively. The second experiment looked at the progression of GNCA titers within individual birds over a 1-yr period. Individual titers increased slightly throughout the study time of the second experiment.