Genetic parameters and trends estimates for reproduction and fitness traits in ‘Threatened’ Nilagiri breed of sheep

Abstract

Abstract The objective of this study was to assess the effect of non-genetic and genetic factors and to estimate the genetic parameters and trends for reproduction and fitness traits of threatened Nilagiri sheep reared under semi-intensive management system. Data used in the present study were collected over a years from 1989 to 2013 (25 years). A total of 6001 individual phenotypic information from about 1129 ewes with variable number of records for each reproduction and fitness traits were used. The reproduction and fitness traits were analysed for the effects of genetic and non-genetic factors, respectively. Fixed effect analysis was carried out using general linear model procedures using SPSS. Variance components and genetic parameters were estimated with univariate analysis by fitting Restricted Maximum Likelihood Method (REML) using WOMBAT programme, by fitting an animal model for all the traits. Three different animal models were fitted by including or excluding maternal effects was used to estimates genetic parameters. Nilagiri sheep had overall mean for all reproduction and fitness traits were estimated. Based on best fitted univariate models, direct heritability estimates, for reproduction and fitness traits ranges from 0.04 to 0.258 were, respectively. Whereas, genetic and phenotypic correlation coefficients between litter size and birth and litter size at weaning were 1.00 ± 0.077 and 0.89 ± 0.007 in Nilagiri sheep which implies the possibility of indirect selection. Genetic changes over the selection period (genetic parameters and genetic trend over the years) suggested that the genetic selection and appropriate management can lead to improvement of Nilagiri sheep.