Genetic parameters and trends for growth traits in Blanco Orejinegro cattle.

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 the years 1980 to 2019 was used. The following data were used: 7,304 birth weight (BW) records, 1,281 records of body weight adjusted to 120 days (W120), 4,791 records of weight adjusted to 240 days (W240), 3,339 records of weight adjusted to 480 days (W480), and 1,364 records of weight adjusted to 720 days (W720). The relationship matrix included 13,612 pure animals belonging to the Colombian Corporation for Agricultural Research - AGROSAVIA and the Producer Network program. A total of 1,224 individuals were genotyped with chips of different densities and all were imputed up to 50,932 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 7 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.