3. Peak mounts received by bullers ranged from 18 mounts/10 min to 34 mounts/10 min and each buller showed dramatic variation in mounts/10 min during subsequent observations (Fig 3a-g).

1
Normal and pathological mounting (bulling
behaviour) in feedlot steers J.L. Clavelle and
J.M. Stookey Large Animal Clinical
Sciences Western College of Veterinary
Medicine University of Saskatchewan, Saskatoon, SK
Jean L. Clavelle
Joseph M. Stookey

• Introduction
• The Buller steer syndrome is characterized by the
  repeated mounting of a steer (referred to as
  the buller) by a group of steers (known as the
  riders) that persistently follow and perform the
  mounting behaviour. Because bullers may suffer
  loss of hair, trauma to the rump and tail head,
  exhaustion, broken bones, or may even die from
  injuries, treatment (removal from the pen) is
  necessary. The annual incidence of buller steers
  is reported to be between 2 and 5 of all feedlot
  steers, however the incidence per pen is
  variable, ranging from 0.0 to 11.2 on a per pen
  basis (Taylor et al., 1997).
• Materials and Methods
• Animals A total of 14 pens of beef steers
  (average pen size of 206 animals per pen) from a
  large commercial feedlot in central Saskatchewan
  were used.
• Methods In the absence of bullers, 12 pens were
  observed in a pre-determined order for a 4-min
  period each daylight hour. The total number of
  mounts was recorded to determine the frequency of
  mounting in the absence of a buller.
• True Buller steers, as determined by our
  definition, received a minimum of 7 mounts and 10
  chin rests and were followed by at least 7 riders
  during 4 minutes.
• Upon finding a True Buller, 4-min observations
  of each pen were suspended in order to observe
  the buller steer. Continuous observation was
  used to record buller mounts and continued until
  sunset, the buller was removed from the pen, or
  until the buller received no mounts for 20
  minutes.
• Results
• 1. Two peaks in mounting were observed in pens
  without bullers one during mid-morning and one
  during late afternoon, prior to sunset (Fig 2).

3. Peak mounts received by bullers ranged from 18
mounts/10 min to 34 mounts/10 min and each buller
showed dramatic variation in mounts/10 min during
subsequent observations (Fig 3a-g). 4.
Peak mounting occurred at a different time of
day for different buller steers (Fig 4).
5. The identification and removal of
bullers may be dependent on the time of arrival
of pencheckers. Seven out of 10 buller steers
were not removed since mounting had either ended
or not yet started by the time feedlot personnel
entered the pen that day. This has serous
implications for the welfare of unidentified
bullers and presents a problem for treating this
condition.
3a
3b
Number of mounts
M
M
M
Time of day (2400 hrs)
3d
3c
M
M
M
M
3f
3e
a) b)
3g
Fig. 1 a) A buller steer being mounted and
surrounded by several steers and b) Buller with
characteristic mud pattern over tailhead, rump
and flank with hair loss over the tailhead.
M
Fig. 3a-g Number of mounts received by the buller
steer during each 10 minute observation period
are shown (individual graphs represent individual
bullers). M represents missed observation.
Yellow bars indicate 10-min observations when
bullers met True Buller criteria.

• Objective
• To describe buller mounting behaviour and normal
  mounting behaviour (not associated with bullers)
  in a large group of feedlot steers

Fig. 4 Each line represents the period of time
individual bullers met True Buller criteria
(bold line) and when buller received mounts
although did not meet True Buller criteria
(thin line).
Conclusions Mounting behaviour in the absence of
a buller shows a pattern similar to the eating
pattern and general activity of cattle. Mounting
frequency is episodic, so the identification and
removal of bullers is dependent on the time
pencheckers enter the pen relative to peaks in
buller mounting.
References Taylor, L.F., Booker, C.W., Jim, G.K.
and Guichon, P.T., 1997. Aust. Vet. J. 75, 45-51.
Acknowledgements This research received
financial support from the Agricultural
Development Fund. We would like to thank the
management and staff of Goldenhill Cattle Co. for
making their animals and facilities available for
this project.