283 Heterosis and its potential influence on pulmonary arterial pressure in beef cattle

Abstract

Abstract High altitude disease (HAD) is a hypoxia-influenced pathologic condition experienced by cattle raised at high elevations (> 1,524 m). Pulmonary arterial pressure (PAP) is a common diagnostic tool used as an indicator of susceptibility to develop HAD. Given PAP is moderately heritable, possibilities to genetically reduce the incidence of HAD are feasible. However, an alternative strategy could be given by heterosis, since non-additive genetic effects have been related to survivability and environmental fitness. Therefore, objectives of this study were to determine heterosis and breed percentage effects on PAP measurements. A total of 1,083 cattle with varying percentages of Simmental, Angus, Hereford and Red Angus breeds were used for the study. Such animals’ available information included PAP records, PAP test date, PAP technician, sex, herd of origin and breed percentages of parents. A general linear model was utilized to estimate the effect of heterosis on PAP. Contemporary group (defined as a combination between herd, PAP date, PAP technician and sex) was included as a categorical fixed effect; whereas the age at PAP measurement and the degree of outcross were included as linear covariates. Similarly, breed effects were estimated by including breed percentages of Simmental, Angus, Hereford, Red Angus and “Other” breeds as linear covariates in the model. The general average for PAP measurements in the entire dataset was 41.29 ± 0.22, with range of 26 and 108 mmHg. The estimated regression coefficient for PAP on heterosis was -1.834 ± 1.676 mmHg/percent of outcross (P = 0.276), whereas, the range of breed effects on PAP was 15.08 mmHg. These results suggested that heterosis had no significant effects on PAP measurements. However, further research including other multibreed populations is required in order to better understand if increased levels of heterozygosity could potentially be related to lower PAP scores.