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DOI: https://doi.org/10.5713/ajas.20.0426    [Accepted] Published online November 25, 2020.
Evaluation of models for estimation of genetic parameters for post-weaning body measurements and their association with yearling weight in Nellore sheep
Satish Kumar Illa1,*  , Gangaraju Gollamoori1  , Sapna Nath2,* 
1Network Project on Sheep Improvement, Livestock Research Station, Palamaner, Sri Venkateswara Veterinary University, Tirupati, Andhra Pradesh 517408, India
2Indian Council of Agricultural Research - National Dairy Research Institute, Division of Animal Production, Southern Research Station, Bangalore, Karnataka 560030, India
Correspondence:  Satish Kumar Illa, Tel: +91-9676607448, Fax: +918579202258, Email: sapna.nath52@gmail.com
Sapna Nath, Tel: +91-9676607448, Fax: +918579202258, Email: sapna.nath52@gmail.com
Received: 20 June 2020   • Revised: 22 July 2020   • Accepted: 20 June 2020
Abstract
Objective
The objective of this study was to obtain (co) variance components and genetic parameter estimates for post-weaning body measurements such as body length, height at withers and chest girth recorded at six (SBL, SHW and SHG), nine (NBL, NHW and NHG) and twelve (YBL, YHW and YHG) months of age along with yearling weight (YW) in Nellore sheep maintained at livestock research station, Palamaner, Andhra Pradesh, India and also the association among body measurements with yearling weight was studied.
Methods
Data on 2,076 Nellore sheep (descended from 75 sires and 522 dams) recorded between 2007 and 2016 (10 years) were utilized in the study. Lambing year, sex of lamb, season of lambing and parity of dam were included in the model as fixed effects and ewe weight was kept as a covariate. Analysis were conducted with six animal models with different combinations of direct and maternal genetic effects using restricted maximum likelihood procedure. Best model for each trait was determined based on Akaike’s Information Criterion.
Results
Moderate estimates of direct heritability were obtained for the studied traits viz., BL (0.02-0.24), HW (0.31-0.49) and CG (0.08-0.35) and their corresponding maternal heritability estimates were in the range of 0.00-0.07 (BL), 0.13-0.17 (HW) and 0.07-0.13 (CG), respectively. Positive direct genetic and phenotypic correlations among the traits and they ranged from 0.07 (YBL-YW) to 0.99 (SBL-SHG, SHG-YW and NBL-YBL) and 0.01 (SBL-YBL) to 0.99 (NBL-NHG), respectively. Further, the genetic correlations among all the body measurements and yearling weight were positive and ranged from 0.07 (YW and YBL) to 0.99 (YW and SHG).
Conclusion
Strong association of chest girth at six months with yearling weight. Further, it is indicated that moderate improvement of post-weaning body measurements in Nellore sheep would be possible through selection.
Keywords: Body Measurements; Heritability; Nellore Sheep; REML


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