Veterinary advice: Role of the vasectomised bull in efficient breeding

This year, with poor milk prices and increased stock numbers putting pressure on all farmers, finding on-farm efficiencies has never been so important.

With the breeding season rapidly approaching for spring calving farms, we need to make some savings.

A cow calving in May is estimated to make €400 less profit per lactation than a cow calving in February, due to higher feed costs and reduced yield.

Pregnancy rates are a combination of conception rates (percentage of inseminations that result in a positive pregnancy) and submission rates (percentage of females presented for insemination in a three-week period).

Over 90% is the acceptable submission rate. Submission rate depends on the number of cows cycling, and heat detection of the cycling cow.

There are many aids to detecting heat: tail paint; scratch cards; Kamar heat detectors; pedometers and movement collars.

But there is no substitute for the teaser bull, on which who I am going to focus for the rest of this article.

A teaser bull is one that has been vasectomised.

A vasectomy is a surgical procedure to cut and seal the “vas deferens”, or the tube used to transport semen from the testicles to the penis, thereby rendering the bull infertile.

Unlike castration, the testicles here are still fully functional, and continue to produce testosterone, so the bull keeps all the characteristics of a bull (size, personality, and libido, or the want to breed), but will not get females pregnant.

The vasectomised bull can still ejaculate but, in short, he is now “firing blanks”.

This bull, wearing a chin ball full of paint, is ideal for seeking out and identifying cows in heat, including many of those silent heats that even the best of stock-men fail to see.

Bull selection is important.

A herd of 100 cows needs at least two vasectomised bulls.

They will be mating with in-heat cows, and exhaustion and injury from overworking is not acceptable.

The surgery can be done in yearling bulls and older, but must be done at least eight weeks prior to the planned start of the breeding date.

Therefore, for 2017 breeding, your bull can be vasectomised from now onwards.

He must be negative for BVD and IBR, and be of good health.

He must have good legs and feet, and be of similar height to the cows he will be mounting.

After the surgery is performed, the bull is not ready to work straight away.

First of all. he needs time to recover from the surgery.

Secondly, he will still have a stock of viable sperm upstream beyond the surgery site.

This semen, in the bull, can remain viable to create pregnancy for almost two months, so waiting eight weeks after surgery to introduce the vasectomised bull is recommended.

If you are under time pressures, another option is to introduce the vasectomised bull to a group of cull cows four weeks after surgery, allowing him to empty himself after about five or six ejaculates.

The infertile bull can now be introduced to cows a little earlier.

For anybody that already has their bull vasectomised for this year, the chin ball should be fitted to the vasectomised bull at least one week before the planned start of breeding, to allow him to get used to it.

During the breeding season, the bull must have his chin ball refilled at least once daily, as the paint will last for only 15-20 mounts.

He will still have the same personality as a breeding bull, so appropriate caution must be taken whenever handling him.

For this reason, fit the vasectomised bull with a nose ring.

The young, inexperienced bull will typically cover the in-heat cow with numerous marks over her head, sides, rump and back, whereas the experienced bull in his second year or after will be more discreet.

The stock-man may have to look a little harder to find the paint marks on the cow’s back after the older bull.

If you have any further questions or would like to arrange bull vasectomy, contact your vet.


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