Effect of pulmonary arterial pressure on reproductive performance in Angus heifers located in south central Wyoming

Pulmonary hypertension (i.e., high altitude disease) occurs in locations above 1,600 m in elevation and causes heart failure and death. Pulmonary arterial pressure scoring is an effective indicator of pulmonary hypertension and high-altitude disease. The objective of this study was to look at the effect of pulmonary arterial pressure (PAP) scoring on reproductive performance in Angus heifers. First service conception (FSC), pregnancy rate, and pulmonary arterial pressure scores were obtained from the Colorado State University Beef Improvement Center for 2,503 Angus heifers between 1995 and 2016. All spring-calving females were exposed to estrous synchronization and one-round of artificial insemination. After a 10-d holding period heifers were exposed to natural service sires for 60 days. First service conception and pregnancy rate traits were determined using ultrasonography via rectal palpation at 30 and 60 days post artificial insemination. Pulmonary arterial pressure scores were collected at ~12 mos of age. Data were analyzed with ANOVA as a completely randomized block design, blocking by birth year. Fixed effect was pulmonary arterial pressure group [high (>42mm Hg) vs. low ( 0.05); however, high pulmonary arterial pressure heifers had lower pregnancy rates compared to low PAP heifers (0.86 vs. 0.91 ± 0.01; P = 0.03). Logistic regression supported these findings, identifying PAP score as a significant predictor of breeding season pregnancy rate (P < 0.05), indicating an inverse relationship between PAP score and pregnancy rate. Cumulatively, results show an unfavorable relationship between heifers with high pulmonary arterial pressure scores and overall pregnancy rate.