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Asian-Australas J Anim Sci > Accepted Articles
DOI: https://doi.org/10.5713/ajas.19.0634    [Accepted] Published online January 13, 2020.
Genetic parameters for worm resistance in Santa Inês sheep using the Bayesian animal model
José Lindenberg Rocha Sarmento1,*  , Francelino Neiva Rodrigues2  , Tânia Maria Leal3  , Adriana Melo Araújo3  , Luiz Antonio Silva Figueiredo Filho4 
1Federal University of Piauí (UFPI), 64.049-550, Teresina, PI, Brazil
2Federal Institute for Education Science and Technology of Piauí (IFPI), 64.750-000, Paulistana, PI, Brazil
3Brazilian Agricultural Research Corporation (Embrapa Meio Norte), 64.006-220, Teresina, PI, Brazil
4Federal Institute for Education, Science and Technology of Maranhão (IFMA), 65.609-899, Caxias, MA, Brazil
Correspondence:  José Lindenberg Rocha Sarmento, Tel: +55-86999244649, Fax: +55-86999244649, Email: sarmento.gema@gmail.com
Received: 6 August 2019   • Revised: 17 September 2019   • Accepted: 21 December 2019
Abstract
Objective
The objective of this study was to estimate the genetic parameters for worm resistance (WR) and associated characteristics, using the linear-threshold animal model via Bayesian inference in single- and multiple-trait analyses.
Methods
Data were collected from a herd of Santa Inês breed sheep. All information was collected with animals submitted to natural contamination conditions. All data (number of eggs per gram of feces, FEC); Famacha score, FS; body condition score, BCS; and hematocrit, HCT) were collected on the same day. The animals were weighed individually on the day after collection (after 12-h fasting). The WR trait was defined by the multivariate cluster analysis, using the number of eggs per gram of feces (FEC), hematocrit (HCT), body condition score (BCS), and Famacha score (FS), of material collected from naturally infected sheep of the Santa Inês breed. The variance components and genetic parameters for the WR, FEC, HCT, ECC, and FS traits were estimated using the Bayesian inference under the linear and threshold animal model.
Results
A low magnitude was obtained for repeatability of worm-related traits. The mean values estimated for heritability were of low-to-high (0.05-0.88) magnitude. The FEC, HCT, BCS, FS, and body weight (BW) traits showed higher heritability (although low magnitude) in the multiple-trait model due to increased information about traits. All WR characters showed a significant genetic correlation, and heritability estimates ranged from low (0.44; single-trait model) to high (0.88; multiple-trait model).
Conclusion
Therefore, we suggest that FS be included as a criterion of ovine genetic selection for endoparasite resistance using the trait defined by multivariate cluster analysis, as it will provide greater genetic gains when compared to any single trait. In addition, its measurement is easy and inexpensive, exhibiting greater heritability and repeatability and a high genetic correlation with the trait of resistance to worms.
Keywords: Famacha; Haemonchus contortus; Heritability; Multivariate Analysis


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