News & Advice

A bull is a bull isn’t he?

Sep 6, 2022 | Bull Fertility, Dairy, Dairy Farm Reproduction, Dry stock

Katrina Roberts, Herd Health Veterinarian

How likely is it really that your bulls would fail a fertility test? Is it worth testing? Do we really need to bother? (Spoiler alert – yes!)

Well, I’ve been crunching the numbers to see what the results of Anexa’s bull fertility testing tells us, so I can provide some data behind why we sound like a broken record around bull testing!

Over the last 7 years of recording our bull testing, we have passed only 89.5% of the bulls tested. Therefore, there is a 1-in-10 chance that the bull you are buying/leasing is not fit for purpose.

There are definitely some seasonal differences when I look at the numbers, with the most common year-to-year variation being the pass rate in yearling bulls. Last year we had a high retest rate and failure rate in this age group with only 75% passing (meaning 1 in 4 failed!). Although we don’t have concrete data on the cause of this variability, the summer/autumn and winter nutrition is most likely a significant factor – the bulls just weren’t able to grow enough, to be fully fertile in time for the mating period.

When we find bulls that are sub-fertile (low fertility) or infertile, it allows you to make decisions based on that information – you might be able to return/replace those bulls, or you may choose to increase your overall bull numbers. The cost of bulls in the current environment may mean that just adding more bulls to your bull team may not be the most economic or enjoyable solution for your farm. Knowing that the bulls you have are good to go at the start is a good insurance policy.

When yearling bulls are not checked before going in with the heifers, they will not be able to get your heifers pregnant at the rate that you want or expect if they are not yet mature enough. I have certainly seen quite a few batches of heifers with less than ideal calving patterns this season (remember our InCalf target is 85% of heifers calved by the end of week 3 after the herd’s planned start of calving (PSC)). With this year’s long autumn dry and poor feed reserves this winter I would predict that we may see a low pass rate in our yearling bulls again this season.

Of course, growth/maturity is not the only concern – bulls can fail a fertility test for a range of reasons. Our bull fertility testing aims to offer a good service (excuse the pun) to identify bulls that are fit for purpose. Testicular size, internal and external genitalia, general health, frame size, and a semen exam are all part of the process (BVD testing, and vaccinations can also be included if not already done).

We see our farmers put so much effort into the front end of mating – getting feed and mineral rights, teaching their team about picking cows on heat, choosing the sires for their herd so carefully, and then once they are past halfway through mating, the bulls are put out and let go for it. You put your trust in the bulls that they can do the rest of the job for you. But is this trust well founded?

Don’t leave it to chance – book your bulls in to be fertility tested. For more information talk to your vet or check out our bull fertility testing web page.

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