343 The relationship between pulmonary arterial pressure phenotypes and oxygen consumption in beef cattle

Abstract The objective of this study was to determine if a phenotypic relationship between pulmonary arterial pressure (PAP) and oxygen consumption exists in beef cattle. Pulmonary arterial pressure is used as an indicator of pulmonary hypertension in cattle which is indicative of the susceptibility to both high-altitude disease and feedlot heart failure of an individual. Cattle with greater PAP are typically hypoxic and have initiated expression of compensatory mechanisms their cardio-pulmonary systems employ to combat this alveolar hypoxia. In turn, this causes an increase in PAP and, ultimately, right-sided heart failure. If hypoxic individuals consume more oxygen as a compensation mechanism, oxygen consumption as a trait could be used as an indicator of the prediction of PAP and feedlot heart failure and would be especially useful for cattle in deep phenotyping systems. Data used in the study included cattle with PAP measures on a total of 132 individuals. The data consisted of both steers (n = 99) and heifers (n = 33) from a ranch located in southern Wyoming at an elevation of approximately 2,195 m. After weaning on the ranch, cattle were transported to Colorado State University’s Agriculture Research, Development and Education Center located in Fort Collins, CO (elevation: 1,558 m). Oxygen consumption was measured using a Greenfeed system (C-Lock, Rapid City, South Dakota). To determine if a relationship exists between oxygen consumption and PAP, a simple linear regression model was used to regress PAP on average daily oxygen consumption. Effects included in the model were sex and phenotypic PAP. Average daily oxygen consumption was measured in kilograms per day and averaged 6.6 ± 1.66 kg with a range of 2.3 to 10.45 kg. Pulmonary arterial pressure averaged 42.6 ± 7.96 mm Hg and ranged from 33 to 81 mm Hg. In this data, sex did not account for a significant amount of variability in phenotypic PAP (P > 0.05). Oxygen consumption did account for a significant amount of variability in PAP (P < 0.05), and it was found that with every 1 kg increase of oxygen consumption, PAP is estimated to increase 1.02 mm Hg. These results indicate that a statistical relationship between oxygen consumption and PAP exists. Although these findings suggest that greater oxygen consumption leads to greater PAP, further research is required to fully comprehend the relationship between beef cattle PAP and oxygen consumption.