Background:

Genetic association studies have been increasingly used in cattle breeding programs. However, inconsistent results -such as positive, negative, or absence of association- across studies restrain reproducibility and proper implementation, propitiating the occurrence of bias.

Objective:

To identify and classify potential sources of bias and determine possible strategies to avoid it in genetic association studies in cattle.

Source of bias in genetic association studies:

Genetic and genomic sources of bias include effects associated with the gene loci governing expression. Sampling-related and statistical biases are related with factors such as stratification and database size.

Strategies to correct bias in genetic association studies:

Correction strategies differ in nature. Genetic and genomic strategies are based on determining the appropriate approach to obtain and report the genetic information. Sampling-related and statistical strategies are based on grouping individuals with certain traits that lead to a reduction in heterogeneity.

Conclusion:

It is necessary to consider the methodology used in previous studies to establish a hierarchy of sources of bias and facilitate decisions on the use of tools to reduce inconsistencies in the results of future studies.

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