PSXI-2 - Preliminary investigations into developmental origins of pulmonary arterial pressure in beef cattle

Abstract: High pulmonary arterial pressure (PAP) is a predisposing factor in the development of high mountain disease in cattle. Since PAP testing is often utilized to prevent disease, a better understanding of the genotype X environmental interactions that drive PAP may lead to the development of additional management and selection strategies. Hypoxia during gestation promotes adaptive fetal programming, a hallmark of which is altered cardiovascular development and disease. However, to our knowledge, no studies have investigated the link between maternal gestational environment and offspring cardiovascular performance as indicated by PAP score. Thus, the objective of this preliminary study was to evaluate the impact of temperature during gestation on yearling PAP in offspring from cattle residing at high altitudes. Yearling PAP data from Colorado State University’s Beef Improvement Center located near Saratoga, Wyoming (7,200 m elevation) was used in the analysis. Data were collected on individual Angus animals born from 1993 to 2021. There were 8,080 individuals with PAP phenotypes averaging 42.23 ± 9.59 mmHg. PAP testing was performed in individuals at an average age of 338.1 ± 46.4 d. Local historical temperature data from September to March, representing the time frame of middle to late gestation, were collected from the (National Oceanic and Atmospheric Administration (NOAA) database) and averaged. This historical average was compared to the yearly mid- to late gestational average temperatures to classify whether an individual animal went through gestation in an above or below-average temperature year. To determine the influence of temperature during gestation on PAP, a single trait linear regression model was used to regress PAP on age at PAP, sex, and temperature classification. The effects of age (P < 0.005), sex (P < 0.0005), and temperature classification (P < 0.05) all accounted for a significant amount of variation in PAP. The least-square means for temperature classification were 42.8 ± 0.51 and 42.3 ± 0.17 for above and below-average temperatures, respectively, which suggests that cows experiencing colder temperatures during gestation produce calves with lower yearling PAPs versus those from cows experiencing warmer temperatures. The internalization of maternal blood during cold temperatures may protect fetal oxygen and nutrient delivery, promoting normal heart development in a high-altitude environment.