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Biomedical subjects

P Y Hester

Publications and source records attributed to P Y Hester.

At least 19 recordsLinked to original sources
PubMed2006

Identification of quantitative trait loci associated with egg quality, egg production, and body weight in an F2 resource population of chickens.

Egg production and egg quality are complex sex-limited traits that may benefit from the implementation of marker-assisted selection. The primary objective of the current study was to identify quantitative trait loci (QTL) associated with egg traits, egg production, and body weight in a chicken resource population. Layer (White Leghorn hens) and broiler (Cobb-Cobb roosters) lines were crossed to generate an F2 population of 508 hens over seven hatches. Phenotypes for 29 traits (weekly body weight from hatch to 6 weeks, egg traits including egg, albumen, yolk, and shell weight, shell thickness, shell puncture score, percentage of shell, and egg shell colour at 35 and 55 weeks of age, as well as egg production between 16 and 55 weeks of age) were measured in hens of the resource population. Genotypes of 120 microsatellite markers on 28 autosomal groups were determined, and interval mapping was conducted to identify putative QTL. Eleven QTL tests representing two regions on chromosomes 2 and 4 surpassed the 5% genome-wise significance threshold. These QTL influenced egg colour, egg and albumen weight, percent shell, body weight, and egg production. The chromosome 4 QTL region is consistent with multiple QTL studies that define chromosome 4 as a critical region significantly associated with a variety of traits across multiple resource populations. An additional 64 QTL tests surpassed the 5% chromosome-wise significance threshold.

Animals↗
PubMed2006

Polymorphisms in vitamin D receptor, osteopontin, insulin-like growth factor 1 and insulin, and their associations with bone, egg and growth traits in a layer--broiler cross in chickens.

Bone strength traits in chickens are gaining importance due to economic losses and welfare concerns associated with bone fractures and other abnormalities. A chicken F2 resource population was generated from layer and broiler genetic lines, and traits relating to bone strength, egg production, egg quality and growth rate were measured in approximately 500 F2 hens. Four biological candidate genes (vitamin D receptor, VDR; insulin, INS; insulin-like growth factor 1, IGF1; and osteopontin, SPP1) were selected for investigation. Single nucleotide polymorphisms (SNPs) were identified for each candidate gene by comparing sequences between grandparent lines. Polymerase chain reaction restriction-fragment length polymorphism or SNaPshot assays were developed to genotype the F2 population and to evaluate associations between each SNP genotype and multiple phenotypes. Significant associations (P < 0.0125) were found between VDR and bone mineral content of the humerus at 35 weeks of age; between IGF1 and SPP1 and 5-week body weight; and between INS and 55-week body weight.

Animals↗
PubMed2005

Validation of dual-energy X-ray absorptiometry in live White Leghorns.

Dual energy x-ray absorptiometry (DEXA) was evaluated for use as a noninvasive tool to monitor skeletal integrity in live laying hens. The objectives of the current study were 1) to validate the use of DEXA in evaluating bone integrity in live birds as compared with excised bones under a normal nutritional regimen as well as in hens fed varying levels of dietary Ca and 2) to correlate densitometric scans with other bone strength criteria and egg traits. Densitometric scans were conducted on the tibia and humerus of live hens at 10-wk intervals from 17 to 67 wk of age. After each scan, bones were excised from euthanized hens to measure breaking strength characteristics and bone ash (experiment 1). Similar measurements were collected at 38, 48, and 58 wk of age from hens fed hypercalcemic (5.4%), control (3.6%), and hypocalcemic (1.8%) diets from 32 to 58 wk of age (experiment 2). The bone mineral density (BMD) and bone mineral content (BMC) between live and excised bone scans were highly correlated (r = 0.85 and 0.92, respectively, P < 0.0001, experiment 1). Densitometric scans of live birds were positively correlated with bone breaking force and bone ash (r = 0.68 and 0.73, respectively, P < 0.001) with little to no correlation with shell traits. In experiment 2, the excised tibial scan had lower BMD and BMC than the live bird (P < 0.01), whereas no difference was detected in densitometric scans of the humerus. The live and excised BMD and BMC of the tibia (r = 0.87 and 0.82, respectively, P < 0.001) and humerus (r = 0.94 and 0.93, respectively, P < 0.001) were highly correlated. Due to the high correlations between live and excised bone scans and the significant correlations of live scans to more traditional invasive bone measurement tests such as bone breaking force and bone ash, we concluded that DEXA is a useful noninvasive tool for evaluating skeletal integrity in live birds.

Absorptiometry, Photon↗
PubMed2005

The effect of pre- and postmolt diets high in n-3 fatty acids and molt programs on skeletal integrity and insulin-like growth factor-I of White Leghorns.

This study investigated changes in bone integrity and circulating concentrations of insulin-like growth factor-I (IGF-I) of hens subjected to 2 distinct molting regimens and fed pre- and postmolt diets high in n-3 or n-6 fatty acids. A dual-energy x-ray absorptiometer determined bone mineral density (BMD) of the tibia and humerus of 45 live hens from 62 to 76 wk of age. Densitometric scans were also conducted in excised tibia and humerus at 66, 71, and 76 wk of age. Concentrations of IGF-I were monitored using an homologous RIA at the same ages. The molting treatments consisted of 10 d of fasting + cracked corn for 7 d + pullet developer diet for 10 d or a nonfasting molt (wheat-middlings-based diet for 27 d). Five weeks prior to and after either molt treatment, birds were fed 1 of 2 diets containing dietary n-6/ n-3 fatty acids ratios of 0.6 or 8.0. At the end of the molt (71 wk of age), tibial BMD decreased 30% in fasted and 11% in nonfasted molt regimens, and the fatty acid content of the premolt diet had no effect on the decline in BMD. The BMD of the humerus also decreased during molt with the exception of hens subjected to a nonfasted molt and fed n-3 fatty acid diets in which their BMD values were similar to or greater (at 73 wk of age) than those of controls during the entire experimental period (treatment by bone by age, P < or = 0.0001). Induced molt affected circulating IGF-I concentrations (treatment by age interaction, P < or = 0.0001), and the response was the same regardless of molt regimen (fasting vs. nonfasting) or diet (n-3 vs. n-6 fatty acids). A decrease in IGF-I 54 h postmolt was noted; however, from 13 to 43 d postmolt, all molted birds had elevated IGF-I as compared with controls. In conclusion, a nonfasted molt as compared with fasted molt was less detrimental to bone mineralization; dietary n-6/n-3 fatty acid ratios in the pre- and postmolt diets had little effect on the decline of skeletal integrity during molt, and circulating IGF-I concentrations were affected by molt.

Aging↗
PubMed2005

Impact of science and management on the welfare of egg laying strains of hens.

Discoveries in behavior and welfare science have improved the health and well-being of egg laying flocks of chickens. The objectives of this review are to highlight research findings in genetics, health, environment, molting, morphological alterations, euthanasia, handling during depopulation, transportation, and harvesting to improve poultry welfare and to provide examples of additional opportunities to continue this progress. Although selection for disease resistance has improved the welfare of birds, use of genetic marker technologies may eventually advance the selection of healthier birds with fewer metabolic disease and cannibalistic tendencies. Animal health and welfare have been improved through development of vaccines, establishment of stringent biosecurity measures, and training of animal caretakers. Industry is currently making adjustments in bird space allocations to allow for less crowded conditions. Continued research in molting shows promise to avoid feed withdrawal regimens for laying hens. Beak trimming by trained personnel improves livability, reduces cannibalism, and should be used when nonaggressive strains are unavailable and when light intensity cannot be controlled. Extension specialists and veterinarians provide information on proper procedures for euthanasia. New systems for euthanasia of spent hens are being implemented by egg producers. New opportunities exist for use of enrichments in production facilities to offer environmental complexity. Further research on how sound and odors affect birds could provide new avenues for improving production systems.

Animal Husbandry↗
PubMed2005

The effect of an induced molt and a second cycle of lay on skeletal integrity of White Leghorns.

The effect of an induced molt and a second egg laying cycle on White Leghorns hen's skeletal integrity was investigated in a series of 3 experiments. Using dual-energy X-ray absorptiometry, bone mineral density (BMD) and bone mineral content (BMC) of the left tibia and humerus were measured in live hens and excised bones and correlated with invasive bone measurement tests, egg traits, and the incidence of broken bones in carcasses of processed hens. The results of all 3 experiments showed that an induced molt was detrimental to skeletal integrity. For hens that were repeatedly scanned throughout the second cycle of lay, the BMD of the humerus never recovered after the molt. Recovery of tibial BMD to premolt values occurred late in the second cycle of lay when egg production was declining. The in vivo BMD scans conducted between 77 and 117 wk of age correlated with bone breaking force and bone ash weight (r = 0.58 and r = 0.65, respectively; P < 0.0001). The percentage of freshly broken bones per bird at the end of processing at 126 wk of age averaged 34% and ranged from 0 to 61%. The incidence of broken bones was negatively correlated with the excised tibial BMD and BMC at 126 wk of age (r = -0.54 and r = -0.53, respectively; P < 0.05). In conclusion, feed withdrawal for 10 d during an induced molt was detrimental to the skeletal integrity of hens, and as BMD and BMC of excised tibia at 126 wk of age decreased in White Leghorns, the incidence of bone breakage increased.

Animals↗
PubMed2005

The effect of an induced molt using a nonfasting program on bone mineralization of white leghorns.

To determine changes in bone mineralization during molt, 66-wk-old White Leghorns were assigned to either a fasted molting regimen using feed removal for 10 d, followed by the ad libitum consumption of cracked corn for 7 d and a pullet developer diet for 10 d or a nonfasted molting regimen lasting 27 d that included the ad libitum consumption of a diet containing 71% wheat middlings and 23% corn. Both molting regimens restricted light to 8 h/d, and water was provided ad libitum. At 28 d postmolt, hens from both molting treatments were returned to a regular egg-laying diet and 16 h/d of photoperiod. Control hens consumed a regular egg laying diet and were kept on 16 h/d of light throughout the study. Using dual-energy x-ray absorptiometry, bone mineral density (BMD) and bone mineral content (BMC) of the left tibia were measured in 7 live hens per treatment immediately prior to, during, and following the molt. Results showed that by 28 d postmolt, BW loss was 22 and 18% in the fasted and nonfasted molting regimens, respectively (P < or = 0.0001). Compared with premolt values, tibial BMD at 28 d postmolt decreased 35 and 18% in the fasted and nonfasted molt groups, respectively (treatment x age interaction, P < or = 0.0001). Similarly, tibial BMC values decreased 39 and 27% in the fasted and nonfasted molt groups, respectively (treatment by age interaction, P < or = 0.01). The tibial BMD and BMC of controls at 28 d postmolt were similar to premolt values. Recovery in tibial BMD and BMC of fasted and nonfasted hens occurred by 126 d postmolt with values similar to controls. These results suggest that a nonfasted molting regimen is less deleterious to tibial BMD and BMC than a fasted molting regimen.

Absorptiometry, Photon↗
PubMed2004

Assessing bone mineral density in vivo: dual energy X-ray absorptiometry.

Dual-energy X-ray absorptiometry can be used as a noninvasive tool to monitor the skeletal integrity of live birds. A pDexa X-ray bone densitometer was used to determine bone mineral densities (BMD) of the left tibia together with the fibula and the humerus of live, unanesthetized birds. Densitometry effectively detected changes in bone integrity of live birds fed varying levels of dietary calcium. Hens consuming 1.8, 3.6, or 5.4% dietary calcium had BMD of 0.147, 0.157, and 0.176 g/cm2 (SEM = 0.005), respectively (linear effect, P < 0.001). Likewise, bone ash weight, breaking force, stress, modulus of elasticity, and eggshell traits also increased linearly in response to increased calcium in the diet (P < 0.05). Densitometric live scans for BMD were positively correlated (P < 0.001) with bone breaking force (r = 0.65) and bone ash (r = 0.77). We also monitored BMD in live Leghorn and broiler females during their life cycle. The tibial BMD of White Leghorns and broilers increased from 15 to 65 wk of age with the BMD of the broiler tibia increasing at a greater rate than that of the Leghorn tibia (line x age interaction, P < 0.0001). A precipitous drop in BMD occurred during an induced molt of Leghorns subjected to 10 d of feed withdrawal. Our long-term goal is to improve skeletal integrity in egg-type chickens by genetic selection for improved BMD. By crossing a broiler with an egg-laying line, an F2 resource population of birds has been developed to identify quantitative trait loci influencing BMD in chickens.

Absorptiometry, Photon↗
PubMed2004

Effects of ovulatory and egg laying cycle on bone mineral density and content of live White Leghorns as assessed by dual-energy X-ray absorptiometry.

Dual-energy X-ray absorptiometry has been validated in our laboratory as a noninvasive tool to assess skeletal integrity in live birds. The first objective of the current study was to determine if there were detectable changes in bone mineral density (BMD) and bone mineral content (BMC) while an egg was being formed in the oviduct. Implications from this experiment would define the time of day scans should be conducted for future experiments. Densitometric scans were conducted on the tibia and humerus of live hens undergoing active egg formation when hens were 0, 5, 15, and 20 h postoviposition at 24, 30, and 40 wk of age. No detectable changes in either the BMD or BMC of the tibia and humerus were observed as the egg was being formed in the reproductive tract at any age measured. These results suggest that densitometric scans may be conducted on bones in live birds at any time during the day, irrespective of the stage of egg formation. The second objective was to monitor the change and degree of variation in skeletal integrity of live birds during the first cycle of egg laying. The humerus and tibia of White Leghorns were scanned repeatedly at 10-wk intervals from 15 to 65 wk of age. The BMD of the humerus increased from 15 to 65 wk of age, whereas the BMD and BMC of the tibia increased from 15 to 55 wk of age, resulting in a bone-by-age interaction (P < 0.001). The BMC of the humerus did not change from 15 to 55 wk of age but increased at 65 wk of age. Age-related increases in BMD and BMC may be due to the inability of dual energy X-ray absorptiometry to distinguish medullary from structural bone. The CV for BMD and BMC of egg-type chickens was greater than 10% after 25 wk of age, which suggested that bone densitometry could be used as an indicator tool in genetic selection with a potential for improving skeletal integrity of birds.

Absorptiometry, Photon↗
PubMed2003

Bone densitometry as an indicator of percentage tibia ash in broiler chicks fed varying dietary calcium and phosphorus levels.

The relative sensitivity of tibia bone mineral content (BMC) and density (BMD), percentage ash (ash), and shear force as indicators for dietary Ca and P was compared in 3-wk-old broiler chicks. One hundred eight 7-d-old chicks were grouped by weight into 6 blocks of 3 cages each with 6 birds per cage. Three corn-soybean meal-based diets were randomly assigned to cages within each block. The diets were low P, medium P, and adequate P and were formulated to contain 4.0, 5.1, and 7.8 g of total P/kg feed, respectively; and 5.1, 6.7, and 10.0 g of Ca/kg feed, respectively. The chicks were fed the experimental diets for 14 d. On d 22, chicks were killed, and tibiae were removed from 3 birds/cage. Weight gain, feed intake, feed efficiency, BMC, BMD, shear force, and ash were determined. The BMC and BMD were determined using dual energy x-ray absorptiometry. Correlations among the various bone status variables and dietary Ca and P were determined. Growth performance criteria and ash increased linearly, and BMC and BMD increased linearly and quadratically as dietary concentrations of Ca and P increased. The correlation coefficient between dietary Ca and BMC, BMD, shear force, or ash was 0.89, 0.91, 0.50, or 0.89, respectively; and between dietary P and BMC, BMD, shear force, or ash was 0.88, 0.91, 0.48, or 0.89, respectively. The correlation coefficient between ash and BMC, BMD, or shear force was 0.92, 0.93, or 0.67, respectively. The correlation coefficients for linear regression between shear force and BMC or BMD was 0.56. The regression model for predicting percentage ash using BMD was as follows: percentage ash = 24 + (240 x BMD) with an r2 of 86%. It is concluded that in broiler chicks, tibia ash, BMC, and BMD may be more sensitive than shear force as indicators of dietary Ca and P concentrations and that BMD as measured by dual energy x-ray absorptiometry may be used to predict percentage of tibia ash.

Absorptiometry, Photon↗
PubMed2003

The use of densitometry to detect differences in bone mineral density and content of live White Leghorns fed varying levels of dietary calcium.

Densitometry was investigated as a noninvasive tool to monitor skeletal integrity in live White Leghorns as an indicator for osteoporosis, a noninfectious disease resulting in mineral loss from the bone. The objectives of the experiment were 1) to assess the ability of densitometry to detect differences in bone integrity in live White Leghorns fed varying concentrations of dietary calcium and 2) to correlate densitometric scans with other bone test methods and production parameters that are sensitive to calcium concentrations in the diet. Hens were fed hypercalcemic (5.4%), control (3.6%), or hypocalcemic (1.8%) diets from 32 to 58 wk of age. A Norland densitometer was used to assess bone mineral density (BMD) and bone mineral content (BMC) of the left tibia and humerus in restrained, unanesthetized hens at 36, 46, and 56 wk of age (experiment 1) and at 38, 48, and 58 wk of age (experiment 2). Bones were excised from hens at 38, 48, and 58 wk of age for breaking strength measurements. Results from the densitometric scans showed that BMD and BMC of the humerus and tibia of live hens decreased linearly when hens consumed diets with decreasing concentrations of calcium (experiment 2). Similar trends in BMD and BMC were detected in experiment 1 at 36 wk of age using BW as a covariate. The results from the densitometric scans were comparable to those obtained from other bone tests commonly used. For example, bone breaking force, stress, and modulus of elasticity decreased linearly as hens consumed decreasing concentrations of calcium. Bone breaking force was correlated with BMD (r=0.65, P<0.001). We concluded that densitometry accurately measures differences in BMD and BMC in live birds fed varying concentrations of dietary calcium.

Absorptiometry, Photon↗
PubMed2002

Utilisation of a sperm quality analyser to evaluate sperm quantity and quality of turkey breeders.

1. A relatively new instrument known as a Sperm Quality Analyzer (SQA) offers a rapid assessment of sperm quality and quantity by providing a sperm quality index (SQI). The SQA measures a combination of the intensity of sperm activity and motile concentration by determining the number and amplitude of sperm movements per second in a capillary tube as detected through light beam interference. 2. Because the SQA has not been tested for its potential use in turkeys, the objective was to determine if the SQA could accurately respond to changes in turkey sperm concentration, viability, and motility in semen collected from turkey breeders. 3. The effect of varying concentrations of sperm on SQI values was evaluated by diluting replicate pools of semen from 4 different aged turkey breeder flocks with saline. Results from all 4 flocks showed that semen dilutions greater than 20-fold resulted in a linear decline in SQI values. 4. Additional in vitro analysis evaluated the effects of turkey sperm viability on the SQI under conditions of constant sperm concentration. Incubated, live sperm was mixed in various proportions with thawed, dead sperm to determine changes in viability. Increased proportions of dead sperm caused a decline in the SQI. 5. To assess sperm motility, turkey semen was incubated under either aerobic (motile) or anaerobic (immotile) conditions. Varied amounts of immotile and motile sperm samples were mixed. A linear increase in the SQI was observed as per cent motile sperm increased. 6. These results indicate that the SQA can respond to differences in turkey sperm concentration, viability, and motility using in vitro analyses.

Animals↗
PubMed2002

Use of a sperm quality analyser on semen of turkey breeders to monitor storage time effects and age-related changes during a reproductive cycle.

1. A relatively new instrument known as a Sperm Quality Analyzer (SQA) offers a rapid assessment of sperm quality and quantity by providing a sperm quality index (SQI). The SQA measures the intensity of sperm activity and motile concentration by determining the number and amplitude of sperm movements per second in a capillary tube as detected through light beam interference. 2. The objectives of the current study were to determine if the SQA could accurately reflect changes in semen quality that occur with prolonged storage of semen and to determine the variation and change in SQI values among individual breeding male turkeys during their semen production cycle. 3. The effect of storage time on SQI values was evaluated by diluting semen with extender and placing the semen on an oscillating shaker at 4 degrees C for 8 h. The SQI values and sperm viability, expressed as % dead sperm, were recorded hourly. The SQI readings declined linearly with increased storage time while % dead sperm increased linearly with increased semen storage. 4. Semen from 220 individual males was analysed monthly for 9 months. Semen diluted 50-fold with saline had lower SQI values during pre- and post-peak phases of production (months 1, 7, 8, and 9 as compared with months 2 to 6 of semen production). The highest SQI values occurred during months 2 to 6. The largest variation in SQI values occurred during months 1 (CV = 26%) and 9 (CV = 31%) with a CV that averaged 16% for the remaining months. 5. Correlation analysis of SQI values for each bird averaged over 9 months with individual male SQIs for each month showed monthly correlation coefficients that ranged from 0.22 to 0.63. 6. These results indicate that the SQA accurately assessed the decline in sperm quality that occurs with prolonged storage of turkey semen and reflected age-related changes in semen quality and quantity that occurred during a semen production cycle of turkey breeders. In addition, the semen quality rank of some turkey breeders in a population changed with age.

Aging↗
PubMed2002

The effect of dietary ascorbic acid on semen traits and testis histology of male turkey breeders.

A 9-mo field trial was conducted to evaluate the effects of dietary L-ascorbic acid (AA) on semen traits of 144 male turkey breeders. Dietary AA treatments were initiated when birds were 30 wk of age. Semen and blood collection began at 32 wk of age. Three treatments with four pens per treatment and 12 birds per pen were fed 0, 75, and 150 mg/kg AA during the first 4 mo of their reproductive cycle. Levels of AA were doubled in the supplemented diets to 150 and 300 mg/kg during Months 5 to 9. Semen traits and blood AA were unaffected by dietary AA. When birds were 65 wk of age, testes were removed from 12 birds per treatment for histological analysis. Multinucleated giant cells (MCG), indicative of degeneration, were observed in the testes of 7 of the 12 control birds but were absent from AA-supplemented birds (P < 0.02). The antioxidant properties of AA may delay formation of these degenerative cells. In conclusion, dietary AA levels employed in the current study did not affect semen traits or testis weight but were associated with reduced formation of MGC in the testes of 65 wk-old breeder toms.

Animals↗
PubMed2001

Systemic distribution of Staphylococcus aureus following intradermal footpad challenge of broilers.

We conducted an experiment with broilers to determine if prior exposure to Staphylococcus aureus would facilitate the systemic infiltration of this pathogen following intradermal footpad challenge with live S. aureus. Litter-raised broilers were sensitized at 3 and 4 wk of age with s.c. injections in the neck with heat-killed S. aureus diluted in polyethylene glycol (PEG). Equal numbers of control birds were injected at the same times with PEG. At 7 wk of age, chicks previously sensitized to killed S. aureus or injected with PEG were injected intradermally in the right footpad with PBS or live S. aureus. The left footpads of all birds were injected with PBS. The difference in thickness between the right and left footpads was determined at 0, 24, and 48 h postchallenge. Blood, liver, spleen, lung, and synovial fluid were collected six times between 1 and 48 h postchallenge to determine the recovery of S. aureus. Sensitized and non-sensitized birds showed footpad swelling following challenge with live S. aureus in the right footpad (P < 0.001). Injection of PBS did not induce footpad swelling. Birds injected in the footpads with live S. aureus as compared to PBS had significantly higher isolation rates of S. aureus in the spleen, liver, and blood; however, recovery of S. aureus from S. aureus-sensitized and PEG-injected birds was not significantly different. Time postchallenge (1, 3, 7, 11, 24, and 48 h) had no significant effect on the recovery of S. aureus. It was concluded that the intradermal challenge of the footpad with S. aureus resulted in systemic infiltration of S. aureus into the spleen, liver, and blood. Prior exposures to killed S. aureus as compared to PEG controls did not affect the systemic distribution of S.

Analysis of Variance↗
PubMed2000

Ascorbic acid supplementation improved antibody response to infectious bursal disease vaccination in chickens.

The purpose of the present study was to determine if supplementation of ascorbic acid (AA) to the diet would have a beneficial effect on infectious bursal disease (IBD) vaccination of chickens for protection against infectious bursal disease virus (IBDV) infection. Two hundred forty specific pathogen-free (SPF) chickens were divided into eight experimental groups. A 2 x 2 x 2 factorial arrangement in a completely randomized design was used; AA supplementation at 1,000 ppm in the diet, vaccination, and challenge were the main effects. Prior to challenge and 10 d after challenge, serum AA concentration, serum corticosterone concentration, ELISA antibody titer to IBDV, body weight, bursa-to-body weight (B:B) ratio, and bursal histological score (BHS) were determined. Nonvaccinated chickens fed a diet supplemented with AA did not exhibit clinical signs or mortality following challenge, whereas AA-unsupplemented counterparts had 100% cumulative morbidity and 30% cumulative mortality. Serum AA levels of AA-supplemented and vaccinated chickens were significantly (P < 0.05) higher than AA-unsupplemented and vaccinated chickens. Fourteen days following vaccination, significantly (P < 0.05) higher ELISA titers to IBDV were observed in vaccinated chickens supplemented with AA as compared to AA-unsupplemented counterparts. Ascorbic acid-supplemented chickens, especially those also vaccinated, had higher body weight gains as compared to the AA-unsupplemented chickens. Ascorbic acid-supplemented chickens challenged with IBDV did not show any clinical signs or mortality. The results suggest that supplementation of AA at 1,000 ppm in the diet has beneficial effects on antibody response to IBD vaccination and body weight gain.

Animals↗
PubMed1999

Delayed-type hypersensitivity reaction induced in broilers by killed Staphylococcus aureus.

A trial was conducted to determine whether the delayed footpad reaction (DFR) induced by killed Staphylococcus aureus in chickens is a delayed-type hypersensitivity (DTH) reaction. Five criteria were used to assess DTH: 1) DFR with a peak response at 24 to 48 h postchallenge, 2) inhibition of monocyte/macrophage migration, 3) lymphocyte blastogenic response, 4) mononuclear cell infiltration at the challenge site, and 5) passive transfer of DFR by splenic lymphocytes. Broilers were sensitized twice with a s.c. injection in the neck of S. aureus antigen (150 microg/bird) diluted in polyethylene glycol at 3 and 4 wk of age. Controls were s.c. injected with polyethylene glycol. At 6 wk of age, a migration inhibition test was conducted before the birds were challenged intradermally with S. aureus antigen (75 microg/bird) in PBS in the right footpad. The left footpad was injected with PBS. The thickness of the footpad was measured at 0, 4, 24, and 48 h postchallenge to evaluate the DFR. After challenge, blood was collected for the lymphocyte blastogenesis assay. Birds were euthanatized, and both footpads were removed for histology. The spleens were collected aseptically; splenic lymphocytes were injected i.v. into recipient birds. Sensitized birds showed an increase in the DFR (P < 0.02) and blastogenic response (P < 0.01) compared with nonsensitized birds. Delayed footpad reaction reached a maximum response at 24 h postchallenge. The in vitro migration of monocytes/macrophages from sensitized birds was significantly inhibited (P < 0.01). The histological appearance of S. aureus-injected footpads was characterized by dermal edema and perivascular infiltrates of small lymphocytes and macrophages. Birds that received sensitized splenic lymphocytes had a significantly pronounced DFR following challenge with S. aureus when compared with birds that received nonsensitized lymphocytes (P < 0.0001). These results indicated that the DFR can be used as a standard in vivo test for cell-mediated DTH reaction induced by killed S. aureus antigen in chickens.

Animals↗