BEPLS Vol 6 [9] August 2017 126 | P age ©2017 AELS, INDIA Bulletin of Environment, Pharmacology and Life Sciences Bull. Env. Pharmacol. Life Sci., Vol 6 [9] August 2017: 126134 ©2017 Academy for Environment and Life Sciences, India Online ISSN 22771808 Journal’s URL:http://www.bepls.com CODEN: BEPLAD Global Impact Factor 0.533 Universal Impact Factor 0.9804 REVIEW ARTICLE OPEN ACCESS Breeding techniques to exploit non-additive gene action for improvement of Livestock Sidharth Prasad Mishra1*, Subhash Taraphder1, Manoranjan Roy1, Uttam Sarkar1, Sanjoy Datta1, Reshma Saikhom1, B P Rosalin2 and Debasish Mohanty3 1 *Dept. of Animal Genetics and Breeding, Faculty of Veterinary and Animal Science, West Bengal University of Animal and Fishery Sciences, West Bengal. Email ID sidpramishra44@gmail.com 2Dept. of Agricultural Metrological, Orissa University of Agriculture and Technology, Bhubaneswar, Odisha 3Dept. of Epidemiology and Preventive Medicine, Orissa University of Agriculture and Technology, Bhubaneswar, Odisha ABSTRACT The architecture of a trait is influenced by both additive and non-additive gene action. In the infinitesimal model, a very large number of genes each with very small additive effects contribute to a trait. Conversely, for a finite locus model, changes in genetic variances owing to truncation selection can be permanent as some or even all loci could get fixed for the favorable allele. That the additive genetic variance should decrease in a finite population because of genetic drift, is a well established principle of evolutionary biology. On the other hand the increase in non-additive variance in a population experiencing genetic drift could be explained by both dominance and epistasis (GCV). The non-additive genetic variation in some traits like viability and fertility is very important in all species of farm animals, and for this the inbreeding depression to a large extent has been observed in these traits. The breeding technologies that used to take advantage of livestock farm animal are cross breeding, terminal sire mating, composite breeding and reciprocal recurrent selection technology. The non-additive genetic variation is very important for viability and fertility in all species of farm animals. Several methods have been adopted to exploit non-additive genetic variation based on a combination of selection and mating that utilized in cattle and buffaloes through cross breeding and in poultry and pigs through terminal sire crossing. Keywords- Breeding techniques, Cross breeding, GCV, Livestock, Non-additive gene effect, Rotational Crossing, Terminal sire crossing Received 30.05.2017 Revised 30.06.2017 Accepted 21.07.2017 INTRODUCTION The genetic architecture of a trait can greatly influence the effect of both additive and nonadditive gene action. In the infinitesimal model, a very large number of genes each with very small additive effects contribute to a trait (25,41). When truncation (or divergent) selection is applied to the infinitesimal model, the change in genetic variance is temporary because linkage disequilibrium is induced between the selected genes. As soon as selection ends, genetic variance tends to be restored to the original level (12). The number of generations of random mating required to restore the level of genetic variance depends on the degree of linkage disequilibrium in the population (21). Conversely, for a finite locus model, changes in genetic variances owing to truncation selection can be permanent as some or even all loci could get fixed for the favorable allele. Recently, the rapid expansion of molecular methods for determination of quantitative trait loci (QTL) has given support for the presence of major genes behind many characters (4,46). Fisher (25) also emphasized that the genetic variation underlying a quantitative trait could be partitioned into different components using a leastsquare principle. The partition includes an additive part due to the additive effect of an individual locus, a dominance part due to withinlocus interactions, and an epistatic portion due to betweenlocus interactions (34). Cockerham (20) and Kempthorne (38) proposed a parameterization to interpret how different genetic effects contribute to the genotypic value, including dominance and epistasis. Cockerham (20) used the concept of two parental populations’ model to construct an F2 reference population with two loci in Hardy–Weinberg equilibrium, and derived an orthogonal partition of the genetic variance in the F2 population. Crow and