INTERNATIONAL JOURNAL OF
POULTRY SCIENCE


Volume - 3 January - 2004 Number - 1

Effects of Dietary Nutrient Density on Performance and Carcass Quality of Male Broilers Grown for Further Processing [Abstract] [Full Text]

Consideration for Dietary Nutrient Density and Energy Feeding Programs for Growing Large Male Broiler Chickens for Further Processing [Abstract] [Full Text]

Shell Characteristics of Eggs from Historic Strains of Single Comb White Leghorn Chickens and the Relationship of Egg Shape to Shell Strength [Abstract] [Full Text]

Dietary Supplementation of Endoxylanases and Phospholipase for Turkeys Fed Wheat-based Rations [Abstract] [Full Text]

Dietary Pentosanase Supplementation of Diets Containing Different Qualities of Wheat on Growth Performance and Metabolizable Energy of Turkey Poults [Abstract] [Full Text]

Extent to Which Crude Protein May Be Reduced in Corn-soybean Meal Broiler Diets Through Amino Acid Supplementation [Abstract] [Full Text]

An Evaluation of the Interaction of Lysine and Methionine in Diets for Growing Broilers [Abstract] [Full Text]

Comparison of Energy Feeding Programs and Early Feed Restriction on Live Performance and Carcass Quality of Large Male Broilers Grown for Further Processing at 9 to 12 Weeks of Age [Abstract] [Full Text]

Expression and Subcellular Location of a Leucine Aminopeptidase of Mycoplasma Gallinarum [Abstract] [Full Text]

Effects of Calsporin® on Turkey Performance, Carcass Yield and Nitrogen Reduction [Abstract] [Full Text]

Turkey Sire Effects on Embryonic Survival and Physiology [Abstract] [Full Text]

Understanding Marek's Disease Immunity: A Continuing Challenge [Abstract] [Full Text]

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International Journal of Poultry Science 3 (1): 1-10, 2004
© Asian Network for Scientific Information 2004


Effects of Dietary Nutrient Density on Performance and Carcass Quality of Male Broilers Grown for Further Processing

E.A. Saleh, S.E. Watkins, A.L. Waldroup and P.W. Waldroup
Poultry Science Department, University of Arkansas, Fayetteville, AR 72701, USA
E-mail: Waldroup@uark.edu

Abstract:

Two trials of identical design were conducted in floor pens to characterize the response of male broilers grown to heavy weights for further processing to dietary nutrient density levels. Nutrient density is defined as the metabolizable energy content of the diet with all essential nutrients maintained in proportion. Ten treatments were utilized with varying nutrient densities obtained by adding poultry oil from 0 to 9% in increments of 1%. Crude protein, amino acids, and other essential nutrients were maintained in proportion to dietary energy levels. Body weights, feed consumed and processing quality were obtained at different intervals up to 63 days of age. Body weight peaked with the diet containing 6% added fat (3267 ME Kcal/ kg, mean of starter, grower, and finisher ME values). Feed intake tended to decrease with increasing nutrient density, but not at a rate commensurate with the change in energy levels. Feed conversion (g gain per g feed) improved as dietary nutrient density increased. Dressing percentage tended to decrease as dietary nutrient density level increased. Abdominal fat and breast meat, both on an absolute weight or percentage of carcass weight basis, remained rather constant when protein was maintained in proportion to energy.

Key words: Broilers, nutrient density, body weight, processing quality


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International Journal of Poultry Science 3 (1): 11-16, 2004
© Asian Network for Scientific Information 2004


Consideration for Dietary Nutrient Density and Energy Feeding Programs for Growing Large Male Broiler Chickens for Further Processing

E.A. Saleh, S.E. Watkins, A.L. Waldroup and P.W. Waldroup
Poultry Science Department, University of Arkansas, Fayetteville, AR 72701, USA
E-mail: Waldroup@uark.edu

Abstract:

Three trials with identical experimental design were conducted to examine the effects of dietary nutrient density and energy feeding programs on male broiler chickens grown to heavy weights for further processing. Diets were formulated to provide a minimum of 107.5% of NRC (1994) amino acid requirements, maintained in proportion to dietary energy levels. Diets with different nutrient density were obtained by adding 0, 3, and 6% poultry oil (PO) while maintaining essential nutrients in a constant balance with energy. Diets within each age period (0 to 21 days, 21 to 42 days, and 42 to 63 days) had similar ratios of metabolizable energy to crude protein. Six feeding programs were obtained by either feeding these three levels of PO continuously to 63 d or by increasing the amount of PO in the diet at 21 d. Live performance was examined at 14, 21, 42, and 63 d and carcass composition was examined at 63 d. Dietary energy levels or feeding programs had no significant effect on body weight except at 42 d, which improved as PO was added to the diet. Feed intake was not significantly affected by feeding various levels of poultry oil or by utilizing different feeding programs. However, feed conversion at all ages showed a significant improvement as the level of supplemental PO increased. Calorie conversion was not affected at 14, 21, and 42 d. At 63 d, calorie conversion was significantly reduced when birds received diets with increased supplemental PO. Neither supplemental PO or feeding program affected the dressing percentage or yield of economically important carcass components at 63 d when examined on an absolute basis or as percentage of carcass weight. Abdominal fat content was not significantly influenced by level of supplemental poultry oil.

Key words: Broilers, energy levels, feeding programs, performance


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International Journal of Poultry Science 3 (1): 17-19, 2004
© Asian Network for Scientific Information 2004


Shell Characteristics of Eggs from Historic Strains of Single
Comb White Leghorn Chickens and the Relationship of
Egg Shape to Shell Strength


K.E. Anderson1, J.B. Tharrington2, P.A. Curtis3 and F.T. Jones4
1Department of Poultry Science, North Carolina State University,
Raleigh, North Carolina, USA 27695
2Department of Food Science, North Carolina State University,
Raleigh, North Carolina, USA 27695
3Department of Poultry Science, Auburn University,
Auburn, Alabama, USA 36849
4Department of Poultry Science, University of Arkansas,
Fayetteville, Arkansas, USA 72701
E-mail: ken_anderson@ncsu.edu

Abstract:

The effect of long term genetic selection on shell characteristics was determined by analyzing eggs acquired from Agriculture Canada: Ottawa Control Strain 5, from a 1950 base population; 7, from a 1959 population; and 10, from a 1972 population. H&N "Nick Chick" 1993 commercial strain was also included because it shares genetic ancestry with the three historic strains. Eggs were collected beginning at 28 wk of age, then every 4 wk through the end of the study at 86 wk of the laying cycle and egg weight, egg height, egg width, shell weight, shell thickness, egg specific gravity, and shell breaking force measured. The relationship of egg shape and weight as factors affecting shell strength were also investigated. Significant differences (P < 0.05) were found between strains for egg shape and a progressive increase in weight and surface area of eggs from the 1950 strain to the current strain. The shape index indicates that the current strain has increased egg size with the greatest increase seen in egg width. The mean breaking force of eggs from the current strain was higher (P< 0.05) than the other strain's eggs with no strain differences in percent shell weight, shell thickness, or specific gravity. A decline in breaking force, percent shell weight, and specific gravity was observed among all the strains over the production period. The results from this study suggest that genetic selection has produced larger eggs that are rounder in shape.

Key words: Genetic selection, shell strength, egg shape index


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International Journal of Poultry Science 3 (1): 20-32, 2004
© Asian Network for Scientific Information 2004


Dietary Supplementation of Endoxylanases and Phospholipase
for Turkeys Fed Wheat-based Rations


A.A. Santos Jr, P.R. Ferket, J.L. Grimes and F.W. Edens
Department of Poultry Science, North Carolina State University,
Raleigh, NC 27695-7608, USA
E-mail: peter_ferket@ncsu.edu

Abstract:

The adverse effects of non-starch polysaccharides (NSP) on turkeys fed wheat-based diets may be alleviated by dietary supplementation of endoxylanase (to reduce the adverse effects of digesta viscosity) or phospholipase (to improve the digestibility of fat). BUTA toms were fed wheat-based diets containing one of 5 enzyme treatments: unsupplemented control, Natugrain Blend® (> 5,500 EXU/kg diet; NB), Lyxasan®-50 (> 2,250 EXU/kg diet; LX50), Lyxasan®-100 (> 5,500 EXU/kg diet; LX100), and Phospholipase (> 500 PLU/kg diet; PL) (BASF, Germany). Each treatment group was assigned to 8 pens containing 12 birds to evaluate growth performance (1-128 d), and 2 pens of 12 birds (excluding LX50) for the apparent metabolizable energy N-corrected (AMEn) and ileum viscosity determination (56-128 d). All enzyme treatments improved growth performance. In comparison to the control, dietary enzyme increased (P < 0.05) BW and decreased 1-128 d feed/gain (2.45 vs 2.37, P < 0.005). PL was most effective in reducing feed/gain during the starting phase and LX100 during the finishing phase, while NB had intermediate benefits throughout the experiment. PL increased AMEn from 9 to 12 wk, while NB and LX-100 resulted in the highest AMEn during the later finishing period. Viscosity was significantly higher for PL than the other treatments (13.5 vs 7.07 cP, P < 0.001). Growth performance and energy utilization of turkeys fed wheat-based diets can be significantly enhanced by phospholipase supplementation of starter feeds and endoxylanase supplementation of growing and finishing feeds. However, enzyme blends may provide a positive response regardless of turkey age.

Key words: Non-starch polysaccharides, wheat, enzymes, turkey, growth performance


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International Journal of Poultry Science 3 (1): 33-45, 2004
© Asian Network for Scientific Information 2004


Dietary Pentosanase Supplementation of Diets Containing
Different Qualities of Wheat on Growth Performance
and Metabolizable Energy of Turkey Poults


A.A. Santos Jr, P.R. Ferket, J.L. Grimes and F.W. Edens
Department of Poultry Science, North Carolina State University,
Raleigh, NC 27695-7608, USA
E-mail: peter_ferket@ncsu.edu

Abstract:

Wheat varies in apparent metabolizable energy N-corrected (AMEn) due to the presence of non-starch polysaccharides (NSP), which can be improved by dietary enzyme supplementation. Poults from 0-17 d-age were fed diets containing various wheat sources (WS) with or without Natugrain Blend® (NB) (BASF, Germany). Five replicate cages of 10 poults were assigned to each eight-soybean-meal/wheat treatment diets and a control soybean-meal/corn diet. The treatments were a factorial arrangement of 4 WS (A, B, C, D) and 2 enzyme levels (0 and 200 mg NB/kg). The WS differed by the degree of frost damage during seed development. Regardless of the source of wheat, NB increased 17 d BW (351 vs 381 g, P < 0.001), decreased 1-17 d FCR (1.55 vs 1.49, P < 0.05), increased AMEn (2,204 vs 2,455 kcal/kg, P < 0.001), and increased apparent nitrogen retention (ANR) (35.0 vs 41.4 %, P < 0.05). No effects of WS were seen on growth performance, but WS A and B had higher (P < 0.05) AMEn than sources C and D (2,396 and 2,460 vs 2,246 and 2,216 kcal/kg, respectively). Gut viscosity was higher (P < 0.05) in poults fed wheat-based diets than the control diet. Enzyme supplementation to the wheat-based diets decreased viscosity (5.57 vs 3.98 cP, P < 0.05) to a level similar to the corn-based control diet, and it resulted in equivalent growth performance. Viscosities were negatively correlated with AMEn. The results demonstrated a positive effect of enzyme supplementation on nutrient utilization and performance of turkeys.

Key words: Wheat, enzymes, growth performance, metabolizable energy, turkey


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International Journal of Poultry Science 3 (1): 46-50, 2004
© Asian Network for Scientific Information 2004


Extent to Which Crude Protein May Be Reduced in Corn-soybean
Meal Broiler Diets Through Amino Acid Supplementation


Jianlin Si2, C.A. Fritts2, D.J. Burnham3 and P.W. Waldroup2
2Poultry Science Department, University of Arkansas, Fayetteville, AR 72701, USA
3Ajinomoto Heartland Lysine Inc., Chicago, IL 60631, USA
E-mail: Waldroup@uark.edu

Abstract:

This study was conducted to explore the extent to which CP can be reduced in corn-soybean meal broiler starter diets by amino acid supplementation while maintaining adequate performance. Using corn and soybean meal of known composition, diets were formulated by linear programming using a minimum of 107.5% of NRC (1994) amino acid recommendations. No minimum CP was required; as each amino acid became limiting crystalline sources were provided to meet the minimum specification. In sequence these were Met, Thr, Lys, Val, Ile, Arg, Phe, and Trp, resulting in eight treatments ranging from 16.61 to 22.48% CP. All diets contained 0.3% sodium bicarbonate and 0.2% aluminum hydroxide as a buffer and antacid. Three additional treatments utilized potassium sulfate to maintain a minimum dietary electrolyte balance (Na + K - Cl) of 250 meq/kg. Each treatment was fed to twelve replicate groups of six male broiler chicks from 1 to 21 d. Reducing CP below 20% while providing indispensable amino acids resulted in a significant reduction in body weight (BW) and feed conversion ratio (FCR). Crude protein content of freeze-dried carcasses declined and fat content increased as diet CP decreased. Feather content (actual weight or % of BW) was not affected until the CP was reduced to less than 18%. Maintaining dietary electrolyte balance at 250 meq/kg in reduced CP diets had no significant effect on any parameter.

Key words: Broilers, crude protein, nitrogen pollution, carcass content


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International Journal of Poultry Science 3 (1): 51-60, 2004
© Asian Network for Scientific Information 2004


An Evaluation of the Interaction of Lysine and Methionine
in Diets for Growing Broilers

Jianlin Si, J.H. Kersey, C.A. Fritts and P.W. Waldroup
Poultry Science Department, University of Arkansas,
Fayetteville, AR 72701, USA
E-mail: Waldroup@uark.edu

Abstract:

Levels of lysine (Lys) and methionine (Met) in excess of NRC recommendations may result in enhanced performance, especially in regard to breast meat yield (BMY). Some people have interpreted the "ideal Protein" concept to suggest that amino acids such as Met should be kept in an "Ideal" ratio with Lys even though Lys may be in excess of actual needs. The objectives of this study were twofold: 1) to evaluate the effects of levels of Lys and Met in excess of NRC recommendations in diets of male broilers grown for further processing; 2) to determine if any interaction exists between levels of Lys and Met when minimum levels are exceeded. Three studies of identical design were conducted. Corn, soybean meal and corn gluten meal of known composition were used to formulate basal diets for 0 to 3, 3 to 6, and 6 to 9 wk which provided a minimum of 110% of NRC (1994) amino acid recommendations other than Lys, Met and TSAA which were at 100% of recommended levels. From the base diets, experimental diets were derived by additions of lysine HCl and DL methionine to provide a factorial arrangement with three levels of Lys (NRC, NRC + 0.15%, NRC + 0.3%) and four levels of Met and TSAA (NRC, NRC + 0.05%, NRC + 0.1%, NRC + 0.15%). Each of the 12 diets was fed to two (trial 1) or four (trial 2 and 3) replicate pens of 50 male broilers (Cobb 500). Birds were weighed and feed consumption determined at 3, 6, 7, 8, and 9 week. Samples of birds were processed at 7, 8, 9 wk for parts yield. Although significant differences in performance were noted among trials due to environmental temperature there was no trial x treatment interaction so data were combined. There were no significant interactions between Lys and Met for any parameter when both were fed equal to or in excess of NRC recommendations. Increasing Lys above NRC recommendations significantly improved BW and FCR at 21 d but not at later ages; BMY was improved by increasing Lys only at 63 d. Increasing Met above NRC significantly improved FCR at 42 and 56d; there was no significant effect of Met levels on BMY at any age. Results of this study suggest that people formulating diet on "Ideal Protein" basis should not elevate the level of Met if lysine is in excess of its minimum needs.

Key words: Broilers, lysine, methionine, carcass yield, breast meat


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International Journal of Poultry Science 3 (1): 61-69, 2004
© Asian Network for Scientific Information 2004


Comparison of Energy Feeding Programs and Early Feed Restriction
on Live Performance and Carcass Quality of Large Male Broilers
Grown for Further Processing at 9 to 12 Weeks of Age


E.A. Saleh, S.E. Watkins, A.L. Waldroup and P.W. Waldroup
Poultry Science Department, University of Arkansas, Fayetteville, AR 72701, USA
E-mail: Waldroup@uark.edu

Abstract:

Six feeding programs for broilers based on level and time of feeding poultry oil (PO) were compared as well as early feed restriction. All diets were formulated to contain a minimum of 107.5% of NRC (1994) amino acid recommendations, maintained in proportion to dietary energy level. Three different energy levels within each age period were obtained by adding 0, 3, and 6% PO and formulating for optimum nutrient density. Diets within each age period (starter, 0 to 21 days; grower, 21 to 42 days; and finisher, 42 to 84 days) had similar calorie:protein ratios. During the restriction period of 7 to 14 d, the birds were given an amount of their respective diets calculated to provide daily maintenance energy requirements. Before and after the restriction period, the birds were offered feed for ad libitum consumption. Body weight, feed consumption, and processing quality were obtained at 63, 70, 77, and 84 d of age. In general, body weight and feed conversion were improved as PO was added to the diet; however, the response was not always significant. Mortality, dressing percentage, abdominal fat, breast, leg, and wing yield did not differ significantly as various levels of PO were fed. In the few instances where there was a significant difference, it did not follow any specific trend among the dietary treatments. There was a significant decrease in the ability to utilize energy by birds grown to 63, 70, 77, or 84 d as the level of PO increased. Feed restriction reduced body weight at 63, 70, and 77 d of age. However, feed conversion was significantly improved and mortality significantly reduced at all ages as compared to birds fed ad libitum. Feed restriction had little impact on abdominal fat. No interaction was observed between PO levels and feed restriction.

Key words: Energy levels, feed restriction, large broilers, further processing


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International Journal of Poultry Science 3 (1): 70-74, 2004
© Asian Network for Scientific Information 2004


Expression and Subcellular Location of a Leucine Aminopeptidase
of Mycoplasma Gallinarum


X. Wan1, S.L. Branton2, M.B. Hughlett1, L.A. Hanson1 and G.T. Pharr1*
1Department of Basic Sciences, College of Veterinary Medicine,
Mississippi State University, Mississippi State, MS 39762, USA
2USDA/ARS South Central Poultry Research Unit,
Mississippi State, MS 39762, USA
E-mail: pharr@cvm.msstate.edu

Abstract:

Mycoplasma Gallinarum is a commensal with a host range that includes most poultry. This property of M. gallinarum may reflect unique mechanisms for colonization and persistence in various hosts. In previous studies a leucine aminopeptidase (LAP) gene candidate was cloned from a M. gallinarum recombinant genomic library and characterized. Here we evaluate the LAP gene from M. gallinarum at the protein level. A recombinant fusion protein was purified and employed as an antigen to immunize chickens to obtain polyclonal anti-LAP serum. The antiserum was utilized to identify the subcellular location by immuoblotting with Triton X-114 partitions of M. gallinarum proteins. Our results of these experiments show that the LAP gene product is located in the cytoplasmic fraction of the M. gallinarum cell.

Key words: Mycoplasma gallinarum, commensal, leucine aminopeptidase, subcellular location


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International Journal of Poultry Science 3 (1): 75-79, 2004
© Asian Network for Scientific Information 2004


Effects of Calsporin® on Turkey Performance, Carcass Yield
and Nitrogen Reduction


E.C. Blair1, H.M. Allen1, S.E. Brooks1, J.D. Firman1, D.H. Robbins1,
Koichi Nishimura2 and Hajime Ishimaru2
1University of Missouri-Columbia, 116 Animal Sciences Department,
Columbia, Missouri 65211, USA
2Quality Technology International, Inc, 11922 Oak Creek Parkway,
Huntley, IL 6014, USA
E-mail: firmanj@missouri.edu

Abstract:

Calsporin®, a probiotic that contains a strain of Bacillus subtilus in a spore form, has been used to increase performance of several species. An experiment was conducted to determine the effects of Calsporin® addition on gain, feed conversion, nitrogen excretion, and salmonella spp. count from the intestinal tract compared to a commercial antibiotic (Bacitracin-Zinc) in male turkeys to market age. Six hundred Hybrid large white tom poults were purchased from a commercial hatchery at day of hatch and randomly allotted into 24 pens, blocked by treatment. Treatments consisted of Calsporin® added at 30 grams per ton of the diet , Bacitracin-zinc at 50 grams per ton or no additive. Birds were housed in an industry standard curtain-sided barn on used pine shavings. Standard corn, soybean meal, animal by-product diets where used for all treatments with nutrient levels based on the 1994 NRC requirements for turkeys. Individual bird weights and pen feed consumption where collected at 21, 42, 63, 84, 105, 126 days. Daily mortality was collected and feed:gain was adjusted to account for mortality. Litter samples where taken from ten random pens at day 63. At 126 days of age three toms per pen where selected based on average pen weight and processed the following day to determine carcass and parts yield. Data were analyzed by analysis of variance (ANOVA) with a randomized block design using the general linear model. By week 12 the treatments that contained either Calsporin® or Bacitracin-zinc had a significantly (p < 0.05) improved gain compared to the treatment without either of the products . For the 0 to 15 and 0 to 18 week phases the birds without additives gained significantly (p< 0.05) less weight compared to all other treatments. No differences in feed efficiency, yield or mortality were observed. Litter samples indicated a reduction in ammonia volitization in Calsporin® fed birds. These data would indicate that Calsporin® may be used successfully as an antibiotic replacement in market turkeys.

Key words: Turkeys, probiotics, lactobacillus, antibiotic use


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International Journal of Poultry Science 3 (1): 80-88, 2004
© Asian Network for Scientific Information 2004


Turkey Sire Effects on Embryonic Survival and Physiology

Vern. L. Christensen, Debbie. T. Ort, Mike. J. Wineland and Jesse. L. Grimes
Department of Poultry Science, College of Agriculture and Life Sciences,
North Carolina State University, Raleigh, North Carolina 27695-7608, USA
E-mail: vern_christensen@ncsu.edu

Abstract:

Sire effects on turkey embryonic survival and growth are not well understood. In avian species, the sire may play only a minor role in embryonic growth as dam effects, mediated through physical and functional qualities of eggs, are thought to be the main determinants. Very little is known of separate dam and sire influences on embryonic survival. The hypothesis was proposed that sires from lines with different BW and embryonic survival rates when mated to an unrelated dam line would produce embryos with different survival, growth and metabolism. Sires from a line with light BW but good embryonic survival (LBW) or sires from a heavy BW line and poor embryonic survival (HBW) were mated to dams of the same unrelated line. Sires from the dam line were included as a control group (Controls). Hens were randomly assigned to sires and inseminated identically at weekly intervals with semen from the assigned sire line. Eight biweekly settings of eggs were placed into incubators to test embryonic survival rates among the sire lines. Tissues were sampled at designated intervals during the experiment to assess the physiological basis for embryonic survival. Contrary to our hypothesis, embryos from the HBW sire line had the best survival compared to LBW and Control. Although LBW poults were from smaller sires, they weighed more than HBW poults. During development LBW sire embryos stored greater amounts of glycogen and lactate in liver and muscle. No effects were seen in cardiac tissue. BW differences were related to greater yolk, but the differences in organ weights and metabolism were clearly related to sire. Thus, sire DNA may direct organ growth and function and influence embryonic survival.

Key words: Sire, dam, embryonic survival, intermediary metabolism


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International Journal of Poultry Science 3 (1): 89-95, 2004
© Asian Network for Scientific Information 2004


Understanding Marek's Disease Immunity: A Continuing Challenge

K.A. Schat
Unit of Avian Medicine, Department of Microbiology and Immunology,
College of Veterinary Medicine, Cornell University, Ithaca NY 14853, USA
E-mail: kas24@cornell.edu

Abstract:

Immune responses to infection with Marek's disease virus (MDV) have been studied intensively since the isolation of MDV in cell cultures and the development of the vaccines around 1970. More than 30 years later, the understanding of the importance of different components of the acquired and innate immune responses is still limited. Antibody responses are less important than cell-mediated immune (CMI) responses due to the cell-associated nature of MDV, although maternal antibodies can interfere with the efficacy of vaccines. The proteins that are detected by the maternal antibodies remain unknown. CMI responses can be directed against a number of glycoproteins as well as immediate early and early proteins, but the relative importance of the responses against individual proteins is unknown. Information concerning the CMI epitopes is still lacking. The importance of antiviral versus antitumor immunity has not been settled. Different types of innate immune responses to MDV (e.g., NK cells, NO, macrophages, interferon-Y ) have been described. Information on the nature of the target cells recognized by NK cells is lacking. Do NK cells recognize specific MDV proteins or is the down regulation of MHC class I antigens sufficient to activate the NK cells? NO can inhibit MDV replication in vitro and in vivo, but infection with very virulent + strains results in increased levels of NO. It is certainly feasible that excessive NO production can lead to pathology. Finally, the relationship between different mechanisms of genetic resistance and immune responses is still incompletely understood.

Key words: Marek's disease, acquired immunity, innate immunity, cytotoxic T lymphocytes


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