Abstract
Aim: This study was aimed to develop the disease resistance broiler chicken lines over two generations (G , G and G ) of 0 1 2 selection for immunocompetence (IC) index by targeting all the facets of immune response traits viz., humoral response (HR) to Sheep red blood cells (SRBC), cell mediated immune response (CMI) to phytohaeagglutinationP mitogen (PHA-P), levels of serum serum immunoglobinG (IgG) and serum lysozyme (LZM) level. Materials and Methods: The SDL Synthetic Dam Line (SDL) broiler line consisting of 303, 204 and 300 birds in G , G and 0 1 G generations, respectively were screened for immunocompetence traits such as humoral response to SRBCs, cell mediated 2 immune response to PHA-P and levels of serum lysozyme by Lysoplate assay and IgG by SRID method, and ranked based on their IC index values. Results: The percent survival rate up to 6 weeks of age in SDL broiler chicken lines were selected for high immunocompetence index (HIC) and low immunocompetence index values (LIC) over two generations (G , G and G ) of selection 0 1 2 and observed that significant differences (P< 0.05) in percent survival pattern in the base population (n= 303) with the highest survivability of 100.00% was observed in 5-6 weeks of age followed by 99.37% and 97.23% in 4-5 and 0-4 weeks of age respectively. In the G generation, significant differences ( P<0.01) was noticed in the selected high and low index lines up to 6 1 weeks of age with the overall survival rate lower in high index lines (93.10% ) as compared to the low index lines (97.62%). Whereas the reverse trend was observed in the G generation that the high index line had significantly (P<0.05) higher survival 2 percent (98.62%) as compared to the low index lines (97.93%). Moreover, the overall survival rate was better substantially over the two generations of divergent immunocompetent index selection of SDL broiler chicken lines. The present investigation revealed that breeding for better immunocompetence status by selection index could lead to better health status in term of improved survival rate in broiler chicken over the generation of selection and further suggested that index selection for more number of generations coupled with economic traits would seem to be a viable option for development of disease resistant chicken lines. Conclusion: Breeding for overall genetic improvement of immunocompetence status by index selection with all the facets of immune system could lead to better survival rate and development of disease resistant chicken.
Highlights
Mortality has always been a great concern in poultry flocks
About 5-6 males and 30-36 females at the high and low index values birds were chosen as parents of G1 high immunocompetence index (HIC) and low immunocompetence index values (LIC) index lines, respectively
The percent survival rates of Synthetic Dam Line (SDL) broiler chicken lines up to the market age (6 weeks) were selected for high and low immunocompetence index by combining HMI, cell mediated immune response (CMI), immunoglobin- G (IgG) and LZM traits over two generations (G0, G1 and G2) of selection are presented in table 1
Summary
Mortality has always been a great concern in poultry flocks. Re-emergence of the poultry diseases cause huge losses to the poultry industry. It is desirable to have disease resistant strains having better genetic combination in association with beneficial traits, for increased fitness to the subsequent generations. In case of natural selection, genetic improvement is slow but constant; whereas in artificial selection, the genetic improvement for single or more traits will bring about noticeable improvement in few or more generations [1,2]. Immunity for disease resistance is a complex genetic trait that is multifaceted [3]. Selection based on an index, combining several immunocom-petence traits seems a viable preposition [4,5].
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