322 Mid-finishing pulmonary arterial pressure compared to late-finishing pulmonary arterial pressure as indicators of heart score.

Abstract Pulmonary arterial pressure measured in beef cattle at a year of age is used to indicate pulmonary hypertension and an individual’s susceptibility to high-altitude disease. When measured at 14 months of age, PAP is related to heart score, an indicator of Bovine Congestive Heart Failure (BCHF). A genetic correlation between 14-month PAP and heart score of 0.94 ± 0.17 has been reported. The relationship between PAP collected around a year of age, at low elevation in a feedyard, and degree of BCHF as indicated by heart score remains unknown. Therefore, the objective of this study was to determine if pulmonary arterial pressure (PAP) measures taken in beef cattle during the mid-finishing period are predictive of heart score. The degree to which an individual is experiencing BCHF at harvest is measured by a heart scoring system developed by Dr. Tim Holt that assesses the degree of physiological remodeling of the right side of the heart. Scores range from 1 to 5, where 1 represents a physiologically normal heart and a 5 represents a heart with severe remodeling. Yearling PAP and heart scores were collected on 107 Angus-influenced steers (n=67) and heifers (n=40). All 107 cattle were finished at the same elevation. Yearling PAP was collected around the average age of 405 days for all cattle. The average PAP was 45.38 mmHg, with minimum and maximum values of 33 and 77 mmHg, respectively. The distribution of heart scores was 33, 60, 12, and 2, corresponding to heart scores 1, 2, 3, and 4, respectively. There were no scores of 5. A simple linear regression model was used to evaluate the relationships between heart score and PAP. Effects in the model for PAP included heart score, sex, and PAP age in days as a linear covariate. Heart score (P< 0.006) and age (P< 0.05) were significant sources of variability in PAP. Yearling PAP least squares means were 46.7 mmHg, 43.4 mmHg, 48.1 mmHg, and 58.7 mmHg, corresponding to heart scores 1, 2, 3, and 4, respectively. In summary, PAP measurements taken around a year of age during an animal’s mid-finishing point may be used as an indicator of BCHF, potentially leading to earlier detection of feedlot heart diseases.