Since 1940, efforts have been made to preserve the Blanco Orejinegro (BON) cattle breed by maintaining gene banks. Nine years ago, a BON genetic improvement program was implemented to increase genetic gain based on control of productivity and the use of performance tests, polygenic and genomic evaluations, and selection indices. The objective of this study was to estimate genetic parameters and trends for growth traits by using polygenic (PM) and genomic-polygenic (GPM) models. Productive information from years 1980 to 2019 was used. The following data were used: 7304 birth weight (BW) records, 1281 records of body weight adjusted to 120 days (W120), 4791 records of weight adjusted to 240 days (W240), 3339 records of weight adjusted to 480 days (W480), and 1364 records of weight adjusted to 720 days (W720). The relationship matrix included 13612 pure animals belonging to the Colombian Corporation for Agricultural Research - AGROSAVIA and the Producer Network program. A total of 1224 individuals were genotyped with chips of different densities and all were imputed up to 50932 SNPs. Polygenic and genomic-polygenic models were used to estimate genetic parameters and correlations between the genetic values estimated by each model. A generalized additive model with smoothing was used to estimate trends of genetic values from 1980 to 2019. Heritabilities between 0.29 and 0.40, genetic correlations between 0.13 and 0.94, and phenotypic correlations between 0.23 and 0.72 were observed. Close-to-zero genetic growth was observed for BW and W120. Genetic trends for the other traits were positive, with higher growth in the last seven years. The heritabilities observed in this population indicate that the traits measured would respond to selection. Greater genetic progress can be achieved in W240, W480 and W720 by continuing with genetic evaluations and developing performance tests and strategies to make genetic material readily available to producers.

Selection indices are used in genetic improvement programs, with the purpose of selectins simultaneous for several economically important traits. The objective of this study was to construct equations for selection indices in the Blanco-Orejinegro (BON) breed and to determine the index that would generate the greatest genetic progress. The information used included birth weight (BW), body weights adjusted to 120, 240, 480, and 720 days old (W120, W240, W240, 480 and W720, respectively), age at first calving (AFC) and interval between first and second calving (IBC) estimated breeding values. Two Smith and Hazel indices were calculated using variances (I1) and literature (I2), with a part two indices designed using information from experts and breeders (I3 and I4). Las características de mayor peso fueron para a*=W120, a**, a****=W720 y a***=W240 respectivamente. In general, the estimated indices obtained similar reliability and expected genetic differences I1 generated a decrease in direct BW. I2 generated the largest increases in BW and AFC. I3 and I4 generated positive changes in growth and reproductive traits, with I3 generating the greatest genetic gains in the population, especially for W240.

Los recursos genéticos se pueden catalogar como el patrimonio biológico más valioso que posee un país. Su conservación debe ser considerada como un compromiso prioritario y necesario para contribuir a la producción agropecuaria. Los bancos de germoplasma de la nación colombiana son repositorios destinados a la conservación de la diversidad genética de diferentes especies de interés agrícola y pecuario.