Bull power for performance, production and profit of Australian beef herds

Bull power for performance, production and profit of Australian beef herds, by Dr Geoffry Fordyce published in FutureBeef 27 August 2020.


The term ‘bull power’, encompasses what defines bulls as being fertile and how to manage them. Bull power has two elements: selection and management to achieve fewer and better bulls. This brief note discusses elements of bull management, as selection of fertile bulls is covered thoroughly by Beggs et al. (2013), (Veterinary bull breeding soundness evaluation), which have been widely adopted. The following discussion assumes the bulls being used have been vetted as sound as per Australian Cattle Veterinarians standards, ie, BullCheck. In addition, reproductive disease management is not presented as it covered extensively elsewhere; however it should be mentioned that bull power adjustment should be complemented with a biosecurity plan that considers vaccinations for your heifers, cows and bulls and potential risks from neighbours.

The problem

Fervently-held paradigms about bull management are one reason for relatively-low adoption of appropriate bull management recommendations. The traditional approach to bull requirements is the use of ‘mating percentages’. Typically, beef producers cite values between 2% and 6% as being necessary. All too often such values are without foundation in evidence-based science, that is, they are traditional opinions.

Opinions are reinforced by beliefs such as those listed and discussed briefly (Table 1).

Table 1. Some facts v myths on bulls

Myths Facts
Mating is 'work'!! Typical language includes 'work load', 'bulls are working hard'. Mating is NOT work. In the absence of bull competition, a mating requires less than a minute of painless diversion from normal eating, ruminating, and sleeping. However, seeking oestrus females does constitute some walking.
Bulls in poor condition is indicative of a ‘high mating load’ or ‘working well’! If pasture is adequate, poor condition of bulls usually indicates high fighting ‘load’, usually because of too many bulls. Experiments conducted in very large paddocks with huge female groups (X,000+) and many rivers under challenging wet season conditions demonstrate clearly that matching mating needs to bull capacity results in fat bulls and no sub-fertility.
Many more bulls are needed in large paddocks with difficult terrain and vegetation The evidence is missing. Oestrus females and bulls seek each other constantly. Just as single humans know where to find each other on Friday nights, it appears cattle have the same capacity despite plenty of hills, rivers, tree cover, distance and poor weather.

One of the primary outcomes of excess bulls is loss of control. As the number of excess bulls increases, the infrastructure and management needed to control them increases. Seasonal mating becomes almost impossible to achieve with excess bulls around. As control is lost, the opportunity for transmission of reproductive diseases increases.

Bulls needed

The simple answer to how many bulls are needed is, minimum requirements plus one for multiple-sire paddocks. This will avoid problems due to acquired bull sub-fertility during mating.

It is NOT recommended that ‘mating percentages’ be the basis of calculations to determine bull requirements. Rather, calculate bull needs by matching mating capacity of bulls to mating requirements of the females. The latter is calculated for peak mating periods.

An example calculation is shown in the box below.

The analysis in Table 2 (below), works through the economic opportunities associated with matching bull capacity to female need. Halving the bull herd, which has virtually zero risk if vetted bulls are used, halves the substantial bull costs/weaned calf.

Table 2. An analysis of bull power for a naturally-mated beef herd.  The top section shows the overall situation.  The bottom section shows six options compared, one per column: using a large v small number of bulls, and use of 0%, 50% or 100% of home-bred bulls.

Mating     Disposal  
First bull mating age 2   Annual bull mortality 2%
Last bull mating age 7   Annual bull cull 10%
Females mated 1000      
Calves branded 700   Finances  
Peak mating duration (days) 30   Net cost/bull bought $5,000
Pregnancies in peak mating 70%   Net cost/bull homebred $1,500
Female cycles/pregnancy 1.5   Net return/bull sold $2,000
Bulls mating/cycling female 2   Annual variable cost/bull $50
Mating capacity/bull/day 5   Annual fixed cost/2 AE $300
Calf wastage 10%   Annual BBSE costs $1,000
Options analysed                
Number of bulls in herd 30 15 30 15   30   15
Bought bulls 100% 100% 50% 50%   0%   0%
Bulls:Mated females 3.00% 1.50% 3.00% 1.50%   3.00%   1.50%
Peak mating/day needs 54 54 54 54   54   54
Bull herd mating capacity/day 150 75 150 75   150   75
Peak mating/bull/day 1.8 3.6 1.8 3.6   1.8   3.6
Minimum bull herd needed 11 11 11 11   11   11
Min new bulls needed/year 2.4 2.4 2.4 2.4   2.4   2.4
Bulls purchased annually 6.7 3.4 3.4 1.7   0   0
Annual business cost for bulls $32,718 $16,859 $20,958 $10,979   $9,198   $5,099
Cost/calf for bulls $47 $24 $30 $16   $13   $7

In the above calculations, an average maximum of five matings per bull each day is used.  Bulls can easily do this if the females are available (See the anecdote box). Every hour, a typical fertile bull produces more than enough sperm (estimated at 50,000/second) for 10 fertile ejaculates. At the bull to female ratios typically used, his mating limits are defined by his libido and access to females. In a typical low-fertility, continuously-mated northern forest herd with 4 bulls per 100 cows and the peak conception period is three months, a bull may get an average of just two mating opportunities per week!  No wonder they then fight viciously for the honour of mating. This HUGE gap between bull capacity and mating needs emphasises the opportunity to reap the benefits of reducing capital investment in bulls.

If the number of bulls being used is too many, almost invariably groups of two or three bulls will be found in the paddock away from cows during peak mating. Bulls establish, patrol and defend defined territories where they have dominance for mating. The most dominant hold territories close to or around waters. Bulls without territories either form small bull groups or become ‘lone raiders’ moving across territories. When bull numbers become excessive, fighting becomes much more intense, resulting in severe injuries such as broken legs. This occurs when the ratio of bulls to females is higher than 3.5%.

A common argument against using fewer and better bulls is that reducing your own bull herd allows easier access of neighbour’s bulls, when the neighbour clearly has vastly too many bulls. In this situation, the business owner must find solutions that suit them both. In regions where infrastructure is limited, taking advantage of improved bull power may best be tackled by a group of neighbouring businesses. (Note introductory comments about biosecurity.)

What happens when mating needs are not considered against bull capacity – An anecdote

About 20 years ago I visited a station to assess heifers in a reproduction study. 1,700    2-year-old Brahman heifers were mustered from one mountainous forest paddock. As I began my ultrasound examinations, it was obvious that almost all females that had reached puberty (44% = 750) were already pregnant – to 6 bulls that were found with the mob. The business had just purchased 53 bulls, waiting in another yard, to go out with these heifers. That capital investment was wasted!

The benefits of fewer and better bulls

A major benefit of fewer and better bulls is better control of mating. There are fewer bulls to source, use and recover.  It opens up the possibility of secure seasonal mating in many situations. It provides a substantial contribution to venereal disease control measures.

Table 2 clearly shows the large financial benefits of fewer bulls. Also shown is the significant further contribution of home breeding objectively-selected bulls, which enables a business to hold genetic improvements achieved by astute selection in the female herd.

Genetic improvement opportunities improve when access is created to bulls of higher genetic merit from the same budget; and, beware of the myth that price indicates genetic merit.

Embarking on the use of fewer and better bulls has an excellent track record with no reported cases of failure where bulls have been vetted according to ACV standards and single-sire mating is not practiced. Therefore, the risk is almost nil. A case study presented by Smith et al. (2016) showed a north Queensland producer reduced bulls from 16 to 4 for a group of 400 maiden heifers, based on matching need to bull mating capacity, saving the purchase of 12 bulls in that year. Adoption of better bull power management has since enabled the business to consistently reduce annual business costs by many tens of thousands of dollars.

More information

In 1992, Dr Dick Holroyd from Queensland DPI led a workshop on bull fertility (Holroyd 1992), which led to extensive detailed bull power research over the following decade (Holroyd et al. 2000; Holroyd et al. 2005). An incomplete series of papers was published from these reports (Bertram et al. 2002; Fitzpatrick et al. 2002; Fordyce et al. 2002; Holroyd et al. 2002; McGowan et al. 2002). All available information was summarised at an annual conference of the Australian Cattle Veterinarians (Fordyce 2002), leading to publication of ACV standards, with a more recent revised edition (Beggs et al. 2013). These publications are the primary evidence-based references on bull fertility for naturally-mated Australian beef herds.


Beggs D, Bertram J, Chenoweth P, Entwistle KW, Fordyce G, Johnston H, Johnston P, McGowan MR, Niethe G, Norman S, Perry V (2013) Veterinary bull breeding soundness evaluation.  Australian Cattle Veterinarians, Brisbane.

Bertram JD, Fordyce G, McGowan MR, Jayawardhana GA, Fitzpatrick LA, Doogan VJ, De Faveri J, Holroyd RG (2002) Bull selection and use in northern Australia. 3. Serving capacity testsAnimal Reproduction Science 71, 51-66.

Fitzpatrick LA, Fordyce G, McGowan MR, Bertram JD, Doogan VJ, De Faveri J, Miller RG, Holroyd RG (2002) Bull selection and use in northern Australia. 2. Semen traitsAnimal Reproduction Science 71, 39-49.

Fordyce G (2002) Bull fertility: Selection and management in Australia. Annual conference proceedings (Editor: G. Fordyce), Australian Association of Cattle Veterinarians, Indooroopilly, Australia.

Fordyce G, Fitzpatrick LA, Cooper NJ, Doogan VJ, De Faveri J, Holroyd RG (2002) Bull selection and use in northern Australia. 5. Social behaviour and managementAnimal Reproduction Science 71, 81-99.

Holroyd RG, Bertram JD, Burns BM, De Faveri J, D’Occhio MJ, Doogan VJ, Fitzpatrick LA, Fordyce G, Jayawardhana G, McGowan M, Miller RG (2000)  Bull selection and use in northern Australia (Bull Power).  Final Report, Project DAQ.104, Meat Research Corporation, Sydney. https://www.mla.com.au/research-and-development/search-rd-reports/final-report-details/Productivity-On-Farm/Bull-selection-and-use-in-northern-Australia/1812

Holroyd RG, Doogan VJ, De Faveri J, Fordyce G, McGowan MR, Bertram JD, Vankan DM, Fitzpatrick LA, Jayawardhana GA, Miller RG (2002) Bull selection and use in northern Australia. 4. Calf output and predictors of fertility of bulls in multiple-sire herds. Animal Reproduction Science 71, 67-79.

Holroyd RG, Bertram, J., Doogan VJ, Fordyce G, Petherick JC, Turner L (2005)  Bull Power: Delivery of adequate normal sperm to site of fertilisation.  Final Report, Project NAP3.117, Meat and Livestock Australia, Sydney. https://www.mla.com.au/research-and-development/search-rd-reports/final-report-details/Productivity-On-Farm/Bullpower-Delivery-of-adequate-normal-sperm-to-site-of-fertilisation/2853

Holroyd RG (1992) Bull Fertility.  Proceedings of a Workshop (Editor: RG Holroyd), Rockhampton, 8-9 September 1992.  Department of Primary Industries, Queensland.

McGowan MR, Bertram JD, Fordyce G, Fitzpatrick LA, Miller RG, Jayawardhana GA, Doogan VJ, De Faveri J, Holroyd RG (2002) Bull selection and use in northern Australia. 1. Physical traits. Animal Reproduction Science 71, 25-37.

Smith DR, Fordyce G, Moravek T (2016) Reduced costs when using recommended bull to female mating ratios. Proceedings of the North Australian Beef Update Conference, 15-18 August 2016, Rockhampton. p205.

Last updated:
30 April 2021