Influence of nutritional management and pulmonary hypertension risk on fertility in developing beef bulls

Commodities

• Animals: bovine

Practices

• Animal Production: animal protection and health

High altitude disease, caused by pulmonary hypertension (PH), presents a significant risk to all segments of beef cattle production, especially to the sustainability of beef operations raising cattle above 1,500 m. Mortality is estimated to be 3-5% among cattle raised at high altitudes; however, can reach 30-40% in lowland cattle brought to higher altitudes or in offspring from untested sires (Holt and Callan, 2007; Bailey et al., 2016). Despite efforts to reduce the frequency of PH, the disease has become increasingly problematic for the beef industry regardless of elevation. Literature has indicated increasing concerns of PH in feedlot cattle at moderate elevations (Stearns et al., 2024). Pulmonary hypertension has direct economic consequences tied to reduced performance, increased morbidity and mortality, and drastically limiting the use of cattle that could provide genetic-based herd improvement. Pulmonary arterial pressure (PAP) testing cattle at altitude is currently the only available method to determine if an animal is susceptible to PH and select against high-risk individuals. Utilizing high-energy diets in developing bulls is a common practice to identify bulls with superior genetics for growth performance. Pre- and post-weaning growth are important for producer profitability; therefore, beef cattle producers are interested in selecting bulls with superior genetics for growth. Furthermore, energy intake is often increased during development to hasten the onset of puberty (Kenny and Byrne, 2018). Previous research, however, has reported excessive fat deposition in bulls had detrimental effects on semen quality (Coulter et al., 1997; Barth and Waldner, 2002; Bartenslager, 2018). Additionally, high PAP has been demonstrated to be associated with increased growth in weaned calves (Shirley et al., 2008) and in feedlot cattle (Neary et al., 2015) suggesting an influence of nutrition and growth on PH. There is currently no published research evaluating the relationship between PH, nutritional management, and bull fertility. Therefore, this proposal aims to evaluate the influence of nutritional management on fertility in beef bulls divergent in PH risk. Additionally, we propose a broader investigation of the impact of PH risk on sire fertility to evaluate the relationship between PH and reproductive efficiency. Determining the relationship between PH, nutrition, and fertility will allow producers to make more informed management decisions, improving animal health, reproductive efficiency, and productivity, as well as the economic sustainability of beef cattle production. Furthermore, improving animal health and reproductive efficiency will allow producers to maintain herd size and productivity necessary for livestock grazing, critical to rangeland health and environmental sustainability in the western U.S. Increasing survivability and performance of cattle managed at high altitudes would increase the number of calves marketed, improving producer profitability and the amount of high-quality protein produced, positively impacting the agriculture community and society as a whole. Results will be disseminated through existing state/regional industry and extension meetings. A series of new stand-alone educational programs will be developed at the University of Wyoming to educate producers and extension professionals on research results, PH, and bull development. Data will also be presented in peer-reviewed publications, extension bulletins, and popular press articles.

Research Objectives:

1. Determine the impact of nutritional management during development on growth performance and semen quality in yearling beef bulls divergent in risk for pulmonary hypertension.
2. Investigate the impact of pulmonary hypertension risk on semen quality in beef bulls.

Education Objectives:

1. To disseminate results of this research, as well as increase the general understanding of brisket disease and bull development to producers in the intermountain west and surrounding regions.
2. Educate producers, industry leaders, and stakeholders on issues surrounding high altitude disease and bull development through experiential learning to improve the sustainability of beef cattle enterprises.
3. Increase awareness of pulmonary hypertension in cattle to producers and industry leaders outside of the intermountain west region.