Genetic Diversity and Population Structure of Sardo Negro Cattle

TL;DR

This paper studies the genetic diversity and population structure of Sardo Negro cattle in Mexico to support conservation and breeding strategies.

Contribution

The study provides a detailed pedigree analysis of the Sardo Negro cattle breed to inform conservation and genetic management.

Findings

The average inbreeding coefficient is 2.5%, with a 0.9% increase per generation.

Only 21 individuals account for 50% of the genetic variability, indicating a founder effect.

Abstract

In animal food production, the breeding of environmentally adapted breeds in different geographical regions is essential to maintain ecological balance and be able to respond to future challenges such as climate change, emerging diseases or resource availability. The Sardo Negro breed of cattle (Bos indicus) originated in Mexico and has been described as a hardy, milk and meat producing breed in tropical climates where high temperatures, humidity and pathogens have a negative impact on non-adapted animals. As a new breed with productive potential, the primary objective is to characterize its genetic diversity and population structure in different herds. To this end, a pedigree analysis was conducted using the genealogical data of 8653 animals. The animals belong to six subpopulations corresponding to different herds located in the Mexican states of Veracruz and Chiapas, where few matings between related animals were observed, as well as a low proportion of individuals with offspring. The gene flow among subpopulations also avoids genetic isolation. This information will help conserve population diversity and maintain the gene pool, phenotype, and resistance to environmental changes through artificial selection.

Livestock production in Mexico takes place in a wide range of agroecological regions, with approximately one-third of the cattle population raised under tropical conditions, where heat stress and disease pressure limit the performance of poorly adapted animals. The Mexican Sardo Negro cattle breed (Bos indicus) is environmentally resilient and is used for both meat and milk production; however, information regarding its population structure and reproductive management remains limited. Therefore, the genetic diversity and population structure of this breed were evaluated through pedigree analysis to support conservation strategies. Genealogical records from 8653 animals belonging to six herds located in the states of Veracruz and Chiapas, Mexico, were analyzed using ENDOG V4.8, PopRep and GRain software. The average inbreeding coefficient was 2.5%, with an increase of 0.9% per generation, a mean generational interval of 7.9 years, and a maximum pedigree depth of nine generations, although pedigree completeness was low in distant generations. The difference between the effective number of ancestors (32) and founders (37) suggests the absence of bottlenecks; however, the fact that only 21 individuals account for 50% of the genetic variability is indicative of a founder effect. Overall, the population exhibits an acceptable level of inbreeding, highlighting the importance of planned mating strategies to maintain genetic diversity and ensure the long-term conservation of the Sardo Negro breed.

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