PROGRESSIVE PRODUCER
BULL MANAGEMENT FOR A SUCCESSFUL BREEDING SEASON by Zach McFarlane, Ph.D., Cal Poly Beef Cattle Production Systems Specialist How often do you think about your herd bulls during your breeding season? Do you know if they are breeding? How do you know if one bull is doing the majority of the work? These are just some of the questions I’ve asked my family and friends during this breeding season. These questions have been driving my research efforts at Cal Poly, where we recently finished analyzing the bull management and selection survey that was sent in the mail to CCA members starting in February 2020. Who knew that the COVID-19 pandemic would change the world as the breeding season was fully underway for many California producers last year? Fortunately, the California beef industry is essential – as evidenced by the responses from CCA members, bull development and management are essential topics for future research and outreach efforts. California’s approximately 660,000 head of beef cattle are dependent on bulls that are “range-ready” to produce calves across the state’s diverse regions. Bulls need to be functional on rugged coastal landscapes, rolling foothills, deserts and in high-elevation terrain. In 2017, approximately 93 percent of cows and 77 percent of heifers were bull-bred exclusively in the United States as indicated by the USDA National Animal Health Monitoring Services (USDA NAHMS) Beef Cow-Calf Management Practices Report. Therefore, we conducted
14 California Cattleman April 2021
a survey to investigate how California bull buyers manage bulls after purchase. Additionally, current research at Cal Poly has focused on bull activity during the breeding season and the effects on bull body weight, body composition and fertility. Bull Management Typically, bulls are fed to increase body condition prior to being sold. In fact, California bull buyers agreed (88 percent of survey respondents) that bull body condition was an important consideration for bull selection and purchase. Producers were also asked how bull body condition was managed after purchase. Most respondents (70 percent) indicated that bull body condition was not reduced prior to the breeding season. Changes in body condition during the breeding season may have an influence on semen quality and is an important management consideration for producers after purchasing a bull. Scrotal circumference is highly correlated with daily sperm production and semen quality. Studies have shown that testicle size, scrotal thermoregulation, and body condition can affect semen quality. Poor or excessive bull body condition negatively impacted the probability of breeding soundness examination passage rates. Furthermore, studies have illustrated that high-energy diets fed to
