FEEDLOT HEART DISEASE: PHENOTYPIC AND GENOMIC INSIGHTS INTO CARDIOVASCULAR REMODELING IN BEEF AND BEEF-ON-DAIRY CATTLE

Abstract

Feedlot heart disease (FHD), also referred to as bovine congestive heart failure, is an increasingly important cause of morbidity and mortality in cattle raised at low to moderate elevations. The objectives of this study were to determine the incidence of heart remodeling in Angus-influenced beef and beef on dairy feedlot cattle and to evaluate phenotypic relationships between heart score and economically relevant production traits. Data were collected from 4,644 cattle harvested between 2020 and 2024, including 2,453 beef cattle and 2,191 beef × dairy cattle raised at elevations ranging from 700 to 1,100 m. Heart scores (HS: 1–5 scale) were assigned at harvest using a standardized postmortem grading system. Additional phenotypes included hot carcass weight (HCW), marbling score, ribeye area (REA), backfat thickness (BF), average daily gain (ADG), and average daily dry matter intake (ADMI). Phenotypic correlations were estimated using Pearson and Spearman methods, and least-squares means were obtained from linear models that accounted for harvest date, sex, and age.The incidence of moderate-to-severe heart remodeling (HS ≥ 3) was greater in beef cattle (23.4%) than in beef on dairy cattle (15.4%). In beef cattle, heart score exhibited weak but significant phenotypic correlations with HCW (r = 0.08), marbling score (r = -0.11), ADG (r = 0.15), and ADMI (r = 0.13; P < 0.05). In contrast, heart score was not significantly correlated with production traits in beef × dairy cattle. Least-squares means revealed that beef cattle with HS 3 had the heaviest carcasses (405.5 ± 2.4 kg), whereas cattle with HS 4 had the lightest carcasses (382.4 ± 43.0 kg; P < 0.05). The heritability estimates for the beef cattle were 0.23(0.05) and the estimate for the beef on dairy cattle were 0.06(0.04). These results showcase that there is a genetic component to cardiopulmonary responses in cattle. There were no identifiable genes that contributed but several significant peaks at chromosome 9, 6,7, and 20 displayed genetic associations with growth traits found in the same SNP windows. This gave evidence that this trait is more likely polygenic and is tightly surrounded by exponential growth in these hyper responding animals. These results demonstrate that heart remodeling is more prevalent in beef than beef on dairy feedlot cattle, not only because of the prevalence rate but also due to the lack of variability in the dataset associated with the beef on dairy cattle. Overall cardiovascular remodeling is associated with unfavorable changes in carcass merit and feedlot performance in severely affected animals. Although phenotypic relationships were generally weak, increasing severity of heart remodeling was associated with reduced carcass quality and performance, emphasizing the importance of incorporating cardiovascular health into future selection and management strategies aimed at reducing the incidence of FHD.