الفهرس 
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Abstract
This work was conducted at the Department of Animal Husbandry and Animal Wealth Development; Faculty of Veterinary Medicine; Alexandria University; between September 2003, and July 2005 on a native Egyptian strain Inshas. The objective of this study was to investigate the response to selection for high antibody titer to inactivated Newcastle disease virus vaccine. Also, to estimate the resulted correlated responses of some productive and reproductive traits, livability, some serum parameters. Also, disease resistance and histopathological findings for challenged birds, in addition to, heritability as well as genetic and phenotypic correlations of the studied traits are estimated.
Response to selection for high antibody titers to was immediate as evidenced by the significant differences (P<0.05) between the high selected line and the control in the second generation of selection.
Actual selection differential, and selection responses for antibody titer (GM) from the first and second generation of selection were 1.59 and 1.21.
Increase (P<0.05) in response and natural immunity to vaccination in the second generation of selection for the high line than the control group (148.59 and 107.68) (7.03 and 4.75); respectively were detected.
Body weights; the adverse effect of selection on Inshas chicks body weights significantly started to decrease (P < 0.05) in the high selected line than the control group at two weeks of age with no differences in body weights due to vaccination within the same line (123.98 vs 124.50 for the high selected vaccinated and non-vaccinated) and (132.24 vs 131.15 in the control
one). Males were higher (P < 0.05) in body weights than females at all ages and generations.
The relative growth rate also, affected by selection during 2-4 weeks of age with significant (P < 0.05) decline than the control (66.13, 67.05, 69.07 and 70.43 for the high selected vaccinated, non-vaccinated, control vaccinated and non-vaccinated, respectively). The same pattern was detected during 6 — 8 and from hatch to eight weeks of age. the vaccination revealed a significant decrease (P < 0.05) in relative growth rate during 4-6weeks within the same line.
The hatchability percentage decreased significantly (P<0.05) in the high selected line than the control one (45.42 and 52.56%), while, fertility percentage was not affected by selection.
Through the first 90 days egg production the egg number and egg mass was increased by selection for high antibody titers to NDV vaccine, in contrast the egg weight decreased in the first generation for the selected line than the reference Inshas strain (38, 46.5, and 1767 vs 36, 48.3 and 1738.8 for egg number (day), weight and mass (gm); respectively). Also, age (day) and body weight at sexual maturity (gm) were decreased in the high selected line than the reference of the strain (140 vs 165 and 1768 vs 1950).
For differential Leukocytic counts only lymphocytes increased in number P<0.05) in the high selected line than the control. Also, Phagocytic activity was increased (P < 0.05) in the high selected vaccinated than the high selected non-vaccinated and the control (vaccinated or non-vaccinated).
Serum parameters; Serum from Inshas of the high vaccinated line was significantly (p < 0.05) higher in total protein (4.09 g/100m1), serum globulin (2.47 g/100m1) and Alkaline Phosphatase (ALP) (4.02) than the control vaccinated group total protein (3.85 g/100m1), globulin (2.25) and ALP (3.65). On the contrary higher significant differences (P < 0.05) for the control vaccinated group were observed for Aspartate amino transferase (71.00) than the high selected line (36.06).
The first generation showed a higher percentage of livability 95.13% than the base generation 91.34%. Livability percentage in the second generation was higher in the high vaccinated line 93.73% than the control vaccinated 91.07%. Moreover, the livability percentage in the non-vaccinated line was higher 88.9 % than that of control non-vaccinated 86.44%.
Histopathological studies revealed that the high selected birds were found to be mildly affected (high disease resistance) in comparison to control during various treatments either challenged after vaccination or with no vaccination.
Heritability estimates of antibody titer to inactivated NDV vaccine were 0.39, 0.51, 0.37 and 0.19 for the base, first, second generation of selection and the control group; respectively. While, realized heritability was 0.41.
Heritability estimates of body weights in base generation were 0.21, 0.15, 0.16, 0.13 and 0.14 for hatch, two, four, six and eight weeks body weights, which get higher. In the second generation of selection (0.45, 0.31, 0.11, 0.24 and 0.12; respectively).
The heritability estimates at base, first, and second generation of selection and control for fertility were 0.35, 0.12, 0.13 and 0.31. While, for hatchability percentage they were 0.24, 0.24, 0.14 and 0.12; respectively. Heritability estimates was high for age at sexual maturity (0.39) and very high for body weight at sexual maturity (0.58).
The heritability estimates of 90 days egg production were 0.16, 0.29 and0.58) for egg number, egg weight and egg mass; respectively.
The estimated heritability for Phagocytic activity and index, as well as, differential Leukocytic counts ranged from 0.01 to 0.34.
Heritability estimates for all blood parameters were low (0.014, 0.021, 0.014, 0.03, 0.062 and 0.157 for serum total protein, albumin, globulin, Alanine aminotransferase, Aspartate aminotrasferase and Alkaline Phosphatase; respectively).
High negative genetic correlation in the. second generation of selection was detected between antibody titers and body weight at two and eight weeks of age (-0.69 and-0.74), medium negative genetic correlation was estimated between antibody tires and body weight at hatch (-0.379), and a low negative for antibody titers and four and six weeks of age (-0.278 and- 0.215).
In the control group of second generation the genetic correlations between antibody titers and body weights at different ages were varied between positive negligible at hatch (0.09) to medium negative at two weeks of age (-0.50).
from these results it would be concluded that substantial improvement of immunological status of chicken against Newcastle disease could be achieved through genetic selection, to high antibody titers without adverse effect on correlated reproductive and productive traits in layer chicken.