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Pedigree analysis of the Nilagiri sheep of South India

Published online by Cambridge University Press:  13 September 2013

R. Venkataramanan ,
A. Subramanian ,
S.N. Sivaselvam ,
T. Sivakumar ,
C. Sreekumar ,
R. Anilkumar  and
M. Iyue
R. Venkataramanan*
Affiliation:
Tamil Nadu Veterinary and Animal Sciences University, Chennai, Tamil Nadu 600 051, India
A. Subramanian
Affiliation:
Tamil Nadu Veterinary and Animal Sciences University, Chennai, Tamil Nadu 600 051, India
S.N. Sivaselvam
Affiliation:
Tamil Nadu Veterinary and Animal Sciences University, Chennai, Tamil Nadu 600 051, India
T. Sivakumar
Affiliation:
Tamil Nadu Veterinary and Animal Sciences University, Chennai, Tamil Nadu 600 051, India
C. Sreekumar
Affiliation:
Tamil Nadu Veterinary and Animal Sciences University, Chennai, Tamil Nadu 600 051, India
R. Anilkumar
Affiliation:
Tamil Nadu Veterinary and Animal Sciences University, Chennai, Tamil Nadu 600 051, India
M. Iyue
Affiliation:
Tamil Nadu Veterinary and Animal Sciences University, Chennai, Tamil Nadu 600 051, India
*
Correspondence to: R. Venkataramanan, Post Graduate Research Institute in Animal Sciences, Kattupakkam, Kancheepuram District, Chennai, Tamil Nadu 603 203, India. email: [email protected]
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Summary

The Nilagiri sheep is a dual utility (fine wool and meat), native to the Nilagiri hills of Tamil Nadu. It is known for its adaptability to high altitude and low input system of rearing. At present, this breed is endangered with less than a thousand numbers existing, of which about 50 percent is maintained at Sheep Breeding Research Station, Sandynallah. Efforts are on to conserve the breed in-situ. Generation interval (GI), pedigree completeness level, inbreeding coefficient (F), average relatedness (AR), effective population size (Ne), and effective number of founders (fe) and ancestors (fa) were studied for the breed. Pedigree analysis was carried out using data available at the research station on 5 051 animals from 1965 onwards using ENDOG ver. 4.8. Higher values of pedigree completeness (more than 80 percent for 5th generation), balance in percent of ancestors between sire and dam pathways and higher equivalent complete generations (7.12) for the reference population were indicative of the depth in pedigree. The GI, F, and AR were 3.36 years, 2.17 and 3.45 percent, respectively. Ne based on maximum number of generations and individual increase in inbreeding was 298.83 and 97.25, respectively. fe and fa were 59 and 41, respectively, for the reference population. F was far from critical values of inbreeding and fe/fa ratio indicated absence of stringent bottlenecks. The effective population size was on the higher end of the range reported for endangered sheep breeds. The knowledge on genetic diversity and effective population size coefficients would support the cause of conservation.

Résumé

Les moutons Nilagiri, bétail à double aptitude (laine fine et viande), sont originaires des montagnes Nilagiri du Tamil Nadu. Ces animaux sont réputés pour leur capacité d'adaptation aux altitudes élevées et aux systèmes d'élevage à faible intensité d'intrants. Avec moins d'un millier de têtes recensées, dont environ la moitié est maintenue à la Station de Recherche en Sélection d'Ovins de Sandynallah, la race est à présent menacée. Des efforts se réalisent pour la conservation in vivo de la race. L'intervalle générationnel (GI), le niveau de complétude de la généalogie, le coefficient de consanguinité (F), la parenté moyenne (AR), la taille effective de la population (Ne) et le nombre effectif de fondateurs (fe) et d'ancêtres (fa) ont été étudiés pour la race. L'analyse de généalogie a été menée avec des données, de 1965 en avant, disponibles à la station de recherche pour un total de 5 051 animaux, en utilisant ENDOG ver. 4.8. Des valeurs de complétude de la généalogie élevées (plus de 80 pour cent sur la cinquième génération), l'équilibre dans les pourcentages d'ancêtres entre lignes paternelles et maternelles et un nombre élevé de générations complètes équivalentes (7,12) pour la population de référence sont signe de la profondeur de la généalogie. GI, F et AR ont été de 3,36 ans, 2,17 pour cent et 3,45 pour cent, respectivement. La Ne basée sur le nombre maximal de générations et l'augmentation individuelle de la consanguinité a été de 298,83 et 97,25, respectivement. Pour ce qui est de fe et fa, les résultats ont été, respectivement, de 59 et 41 pour la population de référence. La valeur de F a été loin d'être critique et le rapport fe/fa a indiqué une absence de goulots d'étranglement sévères. La taille effective de la population s'est située sur l'extrême supérieur de la plage de valeurs rapportées pour les races ovines menacées. Les connaissances en diversité génétique et l'appréciation des coefficients de la taille effective de la population serviraient à soutenir la cause de la conservation.

Resumen

El ganado ovino Nilagiri, de aptitud doble (lana fina y carne), es oriundo de los montes Nilagiri de Tamil Nadu. Estos animales son conocidos por su capacidad de adaptación a altitudes elevadas y a sistemas de cría con bajos insumos. En la actualidad, esta raza está amenazada, quedando menos de un millar de ejemplares censados, de los cuales cerca de la mitad se mantienen en la Estación de Investigación en Mejora de Ganado Ovino de Sandynallah. Se están realizando esfuerzos para la conservación in situ de la raza. Se han estudiado, para la raza, el intervalo generacional (GI), el nivel de compleción del pedigrí, el coeficiente de endogamia (F), el parentesco medio (AR), el tamaño efectivo de población (Ne) y el número efectivo de fundadores (fe) y ancestros (fa). El análisis de genealogía fue llevado a cabo con datos, de 1965 en adelante, disponibles en la estación de investigación para un total de 5 051 animales, usando ENDOG ver. 4.8. Valores altos de completitud del pedigrí (más del 80 por ciento para la quinta generación), el equilibrio en el porcentaje de ancestros entre vías paternas y maternas y un elevado número de generaciones completas equivalentes (7,12) para la población de referencia son indicativos de la profundidad de la genealogía. El GI, F y AR fueron, respectivamente, de 3,36 a|ños, 2,17 por ciento y 3,45 por ciento. El Ne basado en el número máximo de generaciones y el incremento individual en consanguinidad fue de 298,83 y 97,25, respectivamente. Los resultados de fe y fa fueron de 59 y 41, respectivamente, para la población de referencia. El valor de consanguinidad F estuvo lejos de ser crítico y el ratio fe/fa indicó ausencia de cuellos de botella severos. El tamaño efectivo de la población se situó en el extremo superior del intervalo referido para razas ovinas amenazadas. El conocimiento de la diversidad genética y de los coeficientes del tamaño efectivo de población sería de ayuda para la causa de la conservación.

Keywords

pedigree analysisNilagiri sheepeffective population sizeinbreedingrelatednessanalyse généalogiquemoutons Nilagiritaille effective de la populationconsanguinitéparentéanálisis de genealogíaovejas Nilagiritamaño efectivo de la poblaciónconsanguinidadparentesco
Type
Research Article
Information
Animal Genetic Resources/Resources génétiques animales/Recursos genéticos animales , Volume 53 , December 2013 , pp. 11 - 18
Copyright
Copyright © Food and Agriculture Organization of the United Nations 2013 

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