Abstract
The main objective of the present study is to estimate the crossbreeding parameters in respect to serum lysozyme level in broilers. The experiment involved a complete 4×4 diallel design using four synthetic broiler lines namely Coloured Synthetic Male Line (CSML), White Synthetic Male Line (WSML), Coloured Synthetic Female Line (CSFL) and Naked Neck Line (NNL). The lyophilised Micrococcus lysodeikticus suspension was used to detect the lysozyme level in the serum of birds. The data were analysed by least-squares method to find the effects of genetic and non-genetic factors using appropriate model. The crossbreeding parameters for this trait were estimated by complete diallel model assuming the effect of each synthetic line as fixed. The results indicated that additive and non-additive genetic variation attributed to minor genes at many loci is important for the genetic control of serum lysozyme level in chickens. Total non-additive components of variance also showed significant amount of heterosis in crossbred progenies, and therefore exploitation of non-additive component of variance is possible for improvement in serum lysozyme level in broilers. The overall results suggested that for commercial broiler production system, the selection for specialised line on the basis of serum lysozyme level and subsequent crossing of parent lines could enhance the immunocompetence status in relation to serum lysozyme level in crossbred chickens. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 2 : 166-171)
Highlights
MATERIALS AND METHODSApart from the consideration of important production and reproduction traits, the broiler breeding programme takes into account the general health status of the birds.Health is one of the important priorities for genetically improving the productivity of birds in varied systems of rearing (Sheldon, 2000)
The results indicated that additive and non-additive genetic variation attributed to minor genes at many loci is important for the genetic control of serum lysozyme level in chickens
Total non-additive components of variance showed significant amount of heterosis in crossbred progenies, and exploitation of non-additive component of variance is possible for improvement in serum lysozyme level in broilers
Summary
Apart from the consideration of important production and reproduction traits, the broiler breeding programme takes into account the general health status of the birds. Health is one of the important priorities for genetically improving the productivity of birds in varied systems of rearing (Sheldon, 2000). Genetic resistance to disease development is complex and involves several systems of the body with immune system being an important component (Warner et al, 1987; Roitt, et al, 1993). The estimation of serum or egg lysozyme levels in poultry (Coterill and Winter, 1954; Sato and Watanabe, 1976; Saxena, 1993) and cattle (Lie, 1980) were reported. The present work envisages evaluation of crossbreeding parameters involved with inheritance of serum lysozyme level in different synthetic broiler lines and their crosses
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