The Problem with Bullers

A "buller" is a steer that is being persistently ridden by its pen mates. It is a condition that occurs mainly in feedlots, although it can also be seen in stocker steers on pasture. On average, 2% to 5% of steers become bullers, but 10% or more can occur in individual pens. The cost associated with extra management and facilities necessary to handle bullers as well as injury and occasional death has been estimated to be $23-$25 per head (Brower and Kiracofe, 1978; Turgeon and Koers, 1997). Many cattle feeders perceived it as a bigger problem than economics alone can reflect because of the uneven distribution of bullers throughout the year. Heavy periods of bulling activity can lead to excessive demands on labor and pen space and pose a real challenge to management.

Despite the significance of the problem, no underlying physiological mechanism has been identified, and no guaranteed means of eliminating bulling is currently available. However, numerous factors appear to be involved (Brower and Kiracofe, 1978; Turgeon and Koers, 1997; Taylor et al., 1997). They include bunk management, feed composition, weather, season, pen size/density, mixing of cattle and improper/late castration. Additionally, the use of implants has been associated with bulling. Considerable effort has gone into determining which implants and implanting strategies can minimize its occurrence. Ralgro® implants, while enhancing performance, has a minimal effect on the occurrence of bulling.

In a study conducted in Colorado, 93,236 commercially fed steers were implanted with either Ralgro® implants or Synovex® S (Pierson et al., 1976). Results are presented in Table 1. The steers implanted with Ralgro® implants had approximately half the incidence of bullers as those implanted with Synovex S, a savings equal to $4,575.00 per 10,000 head fed, assuming $25 per buller.

Table 1. Incidence of bulling in steers implanted with Ralgro® implants or Synovex S and fed in commercial feedlots in Colorado.
Implant No. of steers No. of bullers Incidence (%)
Ralgro 51,216 1,123 2.19
Synovex S 42,020 1,691 4.2

Similar results were reported by Irwin et al. (1979) where buller incidence in steers implanted with DES (no longer approved for use) and Synovex S were 1.4% and 2.5%, respectively. Buller incidence was only 0.5% in steers implanted with Ralgro® implants. In this case, the steers implanted with Ralgro® implants had only one-fifth the incidence of bullers as those implanted with Synovex S.

Including Ralgro® implants in an E2+TBA (i.e., Revalor®-S or Synovex Plus®) implant program minimized bulling in a series of trials. This was demonstrated in a 147-day trial conducted in a commercial Nebraska feedlot (Booker et al., 1997) with 14,196 steers housed in pens with capacities of up to 600 head each. The steers were implanted with either (1) Synovex Plus on day 0, (2) Ralgro on day 0 and Synovex-Plus on day 70 or (3) Ralgro® implants on day 0 and Revalor-S on day 70. In addition to improving feed efficiency, the use of Ralgro® implants as an initial implant followed by Synovex Plus reduced total buller incidence by half when compared to Synovex Plus alone (9.93% vs. 5.06%). The distribution of bullers over time was also altered (Figure 1). Buller incidence was 3.99% for cattle receiving Ralgro® implants followed by Revalor-S. Again, assuming $25 per buller, a decrease of this magnitude would be worth $12,175.00 per 10,000 head fed.

Figure 1. Buller incidence (percent of cattle on feed) over time for steers implanted on day 0 with Synovex-Plus only or Ralgro® implants on day 0 followed by Synovex-Plus on day 70.

In another study conducted in the same commercial feedlot, buller incidence was reduced from 3.87% to 2.87% when Ralgro® implants were used on day 0 followed by Revalor-S on day 35 compared to a Revalor-S on day 0 with no reimplant (Jim et al., 1998). Delaying the Revalor-S until day 35 (no implant on day 0) did not significantly reduce bullers below that of the steers on the Ralgro® day 0/Revalor-S day 35 treatment.

It is clear from the studies cited that Ralgro® implants offered a significant economic advantage in reducing bullers compared to other implants in this series of trials.


Booker, C.W., G.K. Jim, P.T. Guichon, O.C. Schunicht and R.L. Sibbel. 1997. Comparison of zeranol (Ralgro)/trenbolone acetate (Revalor-S or Synovex Plus) implant programs to an estradiol benzoate/trenbolone acetate (Synovex Plus) implant program in feedlot steers. Intervet/Schering-Plough Animal Health, Union, NJ.

Brower, G.R. and G.H. Kiracofe. 1978. Factors associated with the buller-steer syndrome. J. Anim. Sci. 46:26.

Irwin, M.R., D.R. Melendy, M.S. Amoss and D.P. Hutcheson. 1979. Roles of predisposing factors and gonadal hormones in the buller syndrome of feedlot steers. J. Am. Vet. Assoc. 174(4):367-370.

Jim, G.K., C.W. Booker, O.C. Schunicht, B.K. Wildman and P.T. Guichon. 1998. Evaluation of Revalor-S implant programs on the performance, carcass grading and animal health of yearling steers in Nebraska. Hoechst-Roussel Agri-Vet, Somerville, NJ.

Pierson, R.E., R. Jensen, P.M. Braddy, D.P. Horton and R.M. Christie. 1976. Bulling among yearling feedlot steers. J. Am. Vet. Med. Assoc. 169:521.

Taylor, L.F., C.W. Booker, G.K. Jim and P.T. Guichon. 1997. Epidemiological investigation of the buller steer syndrome (riding behaviour) in a western Canadian feedlot. Aust. Vet. J. 75:45.

Turgeon, A., and W. Koers. 1997. Effects of pen size on the implant response of feedlot cattle. In Symposium: Impact of implants on performance and carcass value of beef cattle. Okla. State Univ. P-957.

Revalor is a registered trademark of Intervet International BV. Ralgro is a registered trademark of Intervet Inc. Synovex and Synovex Plus are registered  trademarks of Zoetis W LLC.