62 *Corresponding author e-mail: mubashir.70011@gmail.com Indian Journal of Animal Sciences 90 (6): 890–892, June 2020/Article https://doi.org/10.56093/ijans.v90i6.104997 Estimation of genetic, phenotypic and environmental trends for production and reproduction traits in a flock of Corriedale sheep M A BABA, T A S GANAI, M A RATHER*, A HAMADANI, S SHANAZ, SAFEER ALAM and NUSRAT N KHAN Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, Jammu and Kashmir 190 006 India Received: 9 May 2019; Accepted: 21 October 2019 ABSTRACT The aim of the present study was to estimate genetic, phenotypic and environmental trends for birth weight (BW), weaning weight (WW), six months body weight (W6), yearling body weight (W12) and age at first lambing (AFL). The genetic trends (gm), respectively, for BW, WW, W6 and W12 were 8, 44.22, 8.05 and 29.45 whereas for AFL it was –0.03 (day/year). The phenotypic trends (gm), respectively for BW, WW, W6 and W12 were –1.3, 36.06, –30.77 and 32.90 whereas for AFL it was 4.39 (day/year). The environmental trends (gm / year) respectively for BW, WW, W6, W12 were –9.3, –8.2, –38.83 and 3.45 whereas for AFL it was –4.36 (day/year). Positive and statistically significant genetic trends were recorded for all studied body weight traits whereas for AFL it was non- significant. Phenotypic trends for all the traits under study were statistically non-significant. Keywords: Corriedale, Environmental trends, Genetic-trends, Phenotypic trend, Sheep, Traits In an attempt to increase the productivity of local low producing sheep in Jammu and Kashmir, cross breeding was adopted for which various breeds of sheep were imported from time to time. These breeds are being maintained at various sheep breeding stations where from elite germplasm is distributed to field agencies for grading up of non-descript animals but for most of the period these breeding stations have acted as closed nucleus flocks. Corriedale is one such breed which was imported around 1970s. It is known for its good mutton conformation, good wool characteristics, relative early maturity and having good range characteristics. This breed is being maintained at sheep breeding farms as a pure breed. Sine this breed has contributed significantly to the increase in mutton production, it is important to study the genetic progress of this breed over the years under temperate agro climatic conditions of Jammu and Kashmir. For this, improvement programs are evaluated through the estimation of genetic trends which depict the effectiveness and efficiency of adopted selection procedures (Hamadani et al. 2019). In recent times, genetic trend is depicted as the average breeding value over years/periods. Harville and Hendeason (1966) described the genetic trend as change in production per unit of time due to change in mean breeding value. Hence, this study was undertaken to evaluate selection and breeding programme of a Corriedale flock maintained at one of the breeding stations. MATERIALS AND METHODS For present study, the data sets were collected from Mountain Sheep and Goat Research Station, SKUAST-K, Shuhama, pertaining to a Corriedale flock, spanning over a period of 25 years from the year 1989 to 2013. The data was collected for traits, viz. birth weight (BW), weaning weight (WW), six month body weight (W6), one year body weight (W12) and age at first lambing (AFL) which were standardized, classified and then subjected to least square analysis for fixed effects of year of birth, sex of animal, type of birth and age of dam. Multiple traits mixed model (DFREML) was used to estimate breeding values which also yielded the variance (covariance) components and corresponding genetic parameters. Convergence was assumed when the variance of likelihood values in the simplex was less than 10–8. In addition, a restart of each analysis was performed with different starting values to attempt to avoid convergence to local maxima. Besides random effects of the animals, fixed effects found statistically significant (P<0.05) during least square analysis were included for estimation of breeding values by using following animal model, Y= Xb + Za + Zm + Zc + e where Y is a n× 1 vector of records; b, vector of fixed effects in the model with association matrix X; a, vector of direct genetic effects with association matrix Za; m, vector of maternal genetic effects with association matrix Zm; c, vector of maternal permanent environmental effects with association matrix Zc, and e, vector of residual (temporary environment) effects. The mean values of expected breeding values (EBVs) were calculated according to years of birth. Genetic trend was estimated by regression of average