The breeding structure for the small ruminant resources in India

Abstract

Intense selection for a few desired traits has resulted in reduction of the effective population size (Ne) in most of the plant and livestock populations across the world. The objective of the research was to assess the impact of Ne on the genetic architecture of the population in a simulated data with variable Ne for general population under selection. Along with this, the estimate of Ne and its ratio to adult breeding population (N_B) in the census data of small ruminants of India were also investigated. Results indicated that the average inbreeding ([Formula: see text]) decreases with increase in Ne; similarly, increase in [Formula: see text] per generation was highest in population with lowest Ne. Correlation of estimated breeding value (EBV) with true breeding value (TBV) was not much affected with effective population size. An effective number of chromosome segments (Me) in the populations under selection were significantly affected by magnitude of Ne, with linear positive relation between Ne and Me. Results on livestock census data revealed that all the sheep and goat breeds have sufficiently large Ne based on derived and actual census data. The median for ratio of effective population size to adult census size in sheep breeds was 0.120 and for goat breeds was 0.131. Karnah and Poonchi sheep shares the status of endangered breeds due to a smaller number of breeding female population and hence need attention for conservation. The Ne was large in sheep and goat due to less selection pressure as a result of low coverage of breed improvement programs, availability of large number of breeding males, and absence of artificial insemination (AI) in the field flocks. The estimates of Ne and its ratio to the adult census size (N_B) excluded several factors such as fluctuating population size and overlapping generations. Study revealed introspection from most of the industrial breeding programs on the issue of Ne for populations under selection. Similarly, in small ruminants, large Ne indicates huge genetic diversity and scope of improvement in the productivity in near future.

Keywords: Census data; Effective population size; Genetic diversity; Sheep and goat breeding.