When it comes to preparing for the next joining period, it’s never too early to start thinking about your bulls.
Often, these blokes are away in a back paddock or at the out-block, out of sight and out of mind.
However, a recent study in south-west Victoria likened bulls to an elite sports team and provided some compelling reasons to prepare in advance to optimise performance.
Current industry recommendations are to use bulls 15 months to four years old, with bulls older than four years twice as likely to fail a fertility test as a bull under four.
Breed should be selected based on factors such as genetics, calving ease, farm preference and intended markets for non-replacement calves.
Bull power needs to be at least three per cent (three bulls per 100 cows), or four per cent if a synchrony program was used.
The key here is to remember that increasing bull numbers alone does not necessarily compensate for poor performers or poor management — a socially dominant bull but sub-fertile bull may serve more cows than other less dominant bulls, but not necessarily sire more calves.
Similarly, a sub-fertile bull team may take longer to get the job done, protracting the joining period and resulting in less early-calvers next calving period, and subsequently poorer herd fertility the next joining period.
Purchased bulls should have a known health and vaccination history. Main diseases of concern are pestivirus (BVDV), vibriosis, leptospirosis, bovine herpes virus and trichomonosis.
Bulls with unknown health status should be tested and screened for venereal diseases before having any contact with your herd.
Where possible, avoid poor conformation, straight hind legs and swollen hocks — these players are at a much higher risk of lameness and are likely to break down mid-season.
Eyes need to be clear in order to visualise cows for serving, and heads and jaws healthy and mobile to ensure normal eating during the joining period.
Temperament and size must also be taken into consideration, ensuring the safety of dairy staff and minimising the risk of injury to other animals on-farm is paramount.
Applying preventative hoof-blocks may have merits in some teams to help prevent or minimise hoof trauma and lameness, but again should not be used to mask any major underlying pathology.
Ideally, your bull team should be introduced to each other no later than two to three months prior to joining. This allows plenty of time for them to establish a social hierarchy well in advance of time, without the added stress of fighting just prior to or during a joining period.
A Veterinary Bull Breeding Soundness Exam (VBBSE) is always advisable prior to joining season commencement, ideally allowing enough time before for any changes to the game plan to be made if one or more of the team require benching.
It can be difficult to source additional players at late notice, and this can put your farm’s biosecurity at risk, and your team’s social hierarchy into turmoil.
Expect a 20 per cent failure rate at time of VBBSE and have adequate numbers of bulls to allow for this.
Defects in semen motility or morphology are not noticeable to the naked eye, and require a VBBSE and laboratory testing to determine.
Issues with sperm may be transient (for example, caused by a period of stress or illness in a bull, often taking up to eight weeks to fully recover) or permanent, compensable (overcome with enough numbers) or non-compensable (increased numbers will not compensate for the defect).
The cost of letting a faulty player go undetected can be disastrous.
Fat bulls can have reduced libido, and excessive scrotal fat deposits reduces semen quality.
Maintaining a moderate body condition score throughout the pre-joining and joining periods is recommended.
Excessive concentrate feeding can lead to laminitis and predispose to arthritis, and bulls are four times more likely to fail a VBBSE if fed grain in the pre-mating period.
Feeding the same quality pasture and forage the milkers receive should be adequate for most paddock bulls.
Depending on your management plan, periodic resting of bulls during the joining period may be warranted, running half the team at a time and rotating weekly, allowing bulls to rest and reducing the risk of breakdown.
How you manage your bench will ultimately depend on the length of your season and the size of your team, but as always it helps to plan ahead.
Finally, it is important to actually watch the game! Serving ability is often not performed during a VBBSE, so it may be down to you to make the final coaching call on whether your players are up to scratch.
You need to ensure bulls are achieving intro-mission and are maintaining acceptable libido, and you should routinely monitor for lameness and injury.
- Dr Lucy Collins
Lucy Collins works as an on-farm veterinarian in Kyabram with Apiam Animal Health, alongside her partner on his 600-cow dairy farm in Dixie. Dr Collins is completing her dairy residency with the University of Melbourne.