Research shows bull temperament can impact productivity

Producers in the beef cattle industry primarily select cattle based on temperament to ensure safety. 

However, emerging research indicates temperament can significantly influence the productivity and economic outcomes of beef operations. 

A bull’s temperament can greatly affect its reproductive success, as stressed or aggressive bulls may undergo hormonal changes leading to reduced libido and lower semen quality, which in turn results in decreased pregnancy rates. 

Research suggests both physical characteristics and temperament should be considered when selecting breeding bulls, as temperament is a highly heritable trait. 

Given its impact on production and reproductive efficiency, temperament is a critical trait in most breeding programs.

Temperament research

Researchers at the University of Tennessee (UT) investigated the relationships among temperament, behavior and growth in bulls during the 2013-14 Junior Bull Test at the UT Bull Testing Station in Spring Hill, Tenn. 

The study focused on 60 Black Angus bulls, and data collected included weight, average daily gain (ADG), frame score and ultrasound measurements of carcass quality. 

Temperament was assessed by assigning scores from one to five, with one indicating docile behavior and five indicating aggressive behavior. 

Data loggers recorded behavioral data, including daily lying time, the duration and frequency of lying and total steps taken over a specified period of time. 

During the 84-day testing period, it was found total lying time between day 59 to day 84 was significantly greater for excitable bulls compared to calm bulls. 

The study also revealed excitable bulls exhibited higher frame scores and ADG than calm bulls, as well as more backfat.

Temperament and reproductive research

Studies indicate reactive female cattle experience higher rates of pregnancy loss and lower success rates in artificial insemination programs.

Similarly, reactive bulls are linked to lower semen quality, reduced ability to regulate testicular temperature and decreased conception rates in natural mating systems. It’s also been observed excitable bulls tend to have a smaller scrotal circumference.

One of the primary hormones released during stress is cortisol, and research has shown blood cortisol concentrations are elevated in temperamental cattle compared to calm ones. 

According to a March 2025 article in the Animal Reproduction Science Journal, a reactive temperament is associated with poor productivity and reproductive performance in bulls.

The article states, “Although temperament does not directly influence testosterone production and sexual precocity in male cattle, there is a trend showing higher cortisol levels and poor reproductive performance are related to greater animal reactivity.” 

Additionally, overly reactive bulls with elevated cortisol levels may face physical challenges when attempting to mount cows. Thus, a calm temperament is crucial for a breeding bull.

“High concentrations of cortisol can suppress the production of luteinizing hormone, influencing the production of testosterone,” the article notes. “A decrease in testosterone concentrations, together with an increase in scrotal temperature, can lead to a transient impairment of semen quality and growth rate.”

Additionally, the increase in scrotal temperature can affect spermatogenesis and semen quality.

Spermatogenesis, the process of sperm production, is directly regulated by testosterone, which is essential for initiating and maintaining the development of mature sperm cells within the testes. Without sufficient testosterone, spermatogenesis cannot proceed properly.

Breeding for temperament

Historically, breeding programs have focused on measurable traits directly linked to profitability, such as body weight. 

However, over time, traits like reproduction and longevity have gained attention, and there is now an increasing interest in behavioral traits that facilitate management.

Given the negative implications of poor temperament in individual bulls – and its impact on the herd through their offspring – producers’ emphasis on this trait is well justified. 

The primary focus should be on selecting a bull with a calm and docile disposition, a trait which is highly heritable and can significantly enhance the overall temperament of the herd, as these genetics are passed on to calves. 

This approach can lead to easier handling, reduced stress and improved safety for both animals and humans, while improving temperament of future progeny.

Implementing management strategies to enhance herd temperament, such as early acclimation to human handling and factoring temperament into selection and culling decisions, will improve cattle performance and the productivity of beef operations with temperamental cattle.

Melissa Anderson is the editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.