# Genetic analysis of disqualifying traits in Nellore cattle

## TL;DR

This study analyzed the genetic basis of disqualifying traits in Nellore cattle to help improve breeding programs and reduce defects.

## Contribution

The study provides new genetic parameter estimates for disqualifying traits in Nellore cattle using Bayesian inference.

## Key findings

- Heritability estimates for traits like depigmentation and navel were high, suggesting genetic selection can reduce defects.
- Genetic trends for most traits declined over time, showing selection is effective in reducing defect incidence.
- The genetic correlation between feet and legs defects and yearling weight was weak and negative.

## Abstract

Morphological defects in beef cattle can compromise animal welfare, functionality and reproductive efficiency, generating economic losses and reducing longevity. Understanding their genetic basis is essential to support selection decisions and prevent the dissemination of defects in breeding programs. This study aimed to estimate the genetic parameters for defects of feet and legs (FL), mouth (MO), chamfer (CH), racial characterization (RC), depigmentation (DP), umbilical hernia (UH), testicular hypoplasia (TH) and navel (NV), evaluated as binary traits at 18 months of age, in Nellore cattle. The data was provided by the CRV Lagoa - PAINT® beef cattle genetic breeding program, which belonged to the company until 2020. The components of (co)variance and breeding values were estimated by Bayesian inference using Animal Models. The genetic correlation between FL and yearling weight (YW) was obtained through a two-trait linear-threshold model. Posterior heritabilities for FL, MO, CH, RC, DP, UH, TH, NV and YW were 0.16 ± 0.03; 0.23 ± 0.04; 0.19 ± 0.03; 0.39 ± 0.04; 0.69 ± 0.04; 0.38 ± 0.12; 0.19 ± 0.04; 0.53 ± 0.04 and 0.45 ± 0.01, respectively. When lineage effect was considered fixed, all traits showed high heritability (> 0.40). The genetic correlation between FL and YW was negative and of low magnitude (-0.06 ± 0.05 without lineage; -0.01 ± 0.09 with lineage). The estimated genetic trends for FL, MO, CH, RC, DP, TH and NV declined over the years, indicating a gradual reduction of their incidence due to selection, while UH presented unstable pattern. Overall, the results indicated that including disqualifying traits in breeding programs can lead to reduced occurrence of morphological defects in Nellore herds.