Bull Soundness

EVALUATION AND BULL BUYING

Written by: Philip Edwards MBA, Beef Breeding Services Pty Ltd, Rockhampton.

How many times have you heard an auctioneer say, “He’s all semen tested, and 70% on the morphology, anyway there buyers, kick him away there, $50,000?”. Magically, as if the agent has guaranteed the everlasting soundness and fertility of this bull, we jump into bidding because we like the look of this amazing young sire, and the agent said he is “70% on the morph”. Amazingly, this has became the “norm”, and not for one second does the agent or the average buyer fully know what “Morphology” is, nor what is the minimum percentage requirement or how to correlate the information to their breeding program, just the fact the bigger the percentage, the better he must be.

Whilst morphology is highly important, and I will outline further of its relevance, often the overall soundness evaluation of a bull is over looked by bull breeders. It’s just a case of wanting to meet the minimum requirements for a sale, and bull buyers not demanding greater information to assist with their decision making.

Some years ago, I was part of a pastoral company that adopted the “Australian Cattle Vets (ACV), Veterinary Bull Breeding Soundness Evaluation (VBBSE)” as part of their yearly bull purchasing and sire testing (pre-putting bulls out with the herd). The adoption of the VBBSE for all bulls prior to joining was brought about by poor herd reproductive performance.

A change in genetic diversity was introduced by purchasing 8 young bulls from the Dubbo bull sales. These young sires were selected and purchased solely on type and EMA information, without soundness evaluation. Therefore, on arrival to the station, these eight 2 year old bulls underwent the VBSSE. When tested, 5 of the bulls had seminal infections, 3 passed motility, and only two of those 3 passed morphology. All bulls passed their physical examination, and on service ability, 7 of the 8 could physically serve a cow correctly, the 8th bull did a lot of mounting but was unable to actually service a cow. This bull, whenever in the position to thrust, would back off the cow. Even following a retest 2 weeks later, and after being out with females, this bull failed. Had all this information been available at the auction, clearly only 2 of the 8 bulls would have been purchased.

Honestly, it is a lucky dip without having something tangible to go by, and the VBBSE when conducted on your sale bulls, provides the best information for your catalogue, and for the buyer the reduced rick of purchasing a bull that could be sub-fertile.

Understandably, we all look for something different in the physiology of our bulls to suit our herd, and not all of us will agree on the choice of bull - just look at show ring judging and the varied opinions. This is all subjective and left to the eye, that is our individual choice, but it’s what you can’t see with the eye that produces the offspring, and too often we let our hearts rule our heads in this area.

At Beef Breeding Services, we collect and process a lot of semen at our collection centre in Rockhampton and our semen processing and testing laboratory in Brisbane. Not to mention the hundreds of bulls our vet soundness tests on farm, as well as our on-farm semen collection and processing service. We get to see it all, including sub fertile bulls that would not have passed a VBBSE.

So, what does a VBBSE consist of? Importantly, the ACV provides certification to their affiliated members, who have inspected and examined 500 or more bulls, passed both a theory and practical exam, the standing of an “accredited” VBBSE Vet.

The Physical Examination

A physical examination not only includes the structural soundness and appearance of a bull, but includes his tractability and gait, scrotal circumference, and an examination of the internal and external genitals.

Simple things such as a scrotal circumference are important, as under normal working conditions, a bull can lose 2cm in circumference in a 6-8 week joining period.

Why is this significant? Once a 2 year old bulls testicular circumference hits 28 cm, he can become sub fertile.

Semen Evaluation

A crush side collection is taken by either electroejaculation (most common) or manual palpation, and then assessed under a microscope. By viewing the collected semen under the microscope, the vet is able to ascertain if the semen is viable to obtain fertilisation. During this assessment the vet evaluates the motility, which is the activity of the sperm, generally referred to as the swirl, and the progressiveness of the sperm. Colour and density of the collection is recorded as well as evidence of infections (Pus).

During the crush side assessment some morphological issues may be identified, however a detailed report provided from laboratory analysis is the only way to ensure the percentage of good viable sperm are present with minimal defective sperm. The AVA has determined through research that for a sample to pass their testing, it must have a minimum of 30% progressive motile sperm. Through the use of a laboratory microscope, laboratory staff view the structure of the sperm cells to determine the percentage of normal sperm to the percentage of abnormal sperm in an ejaculate. This evaluation provides valuable information as to the viability of a sire to produce calves, to which the AVA have set standards for sire mating based on the percentage of normal live sperm.

>70% Single sire mating and Semen collection for AI >50% Suitable for multiple sire joining groups

Semen morphology is regarded as a heritable trait, and research has linked it to a number of key reproduction traits:

- Indicator of bull fertility. - Maturity and fertility of daughters. - The ability of daughters to return to oestrus after calving.

As producers, by utilising this information in your breeding objectives, and identifying and using bulls of good fertility/morphology, you can reduce the anestrous period of your females, which can potentially increase the ability to have more calves born at the beginning of your calving cycle. Obviously seasonal conditions and animal health must be accounted for.

Depending on breed, it has been noted that 20-40% of bulls will fail a morphology test, therefore while a bull may pass a crush side motility test, he may fail a full VBBSE. A bull must pass both fertility tests to be deemed “fertile”.

Fig 1. Examples of various qualities of semen

There are two terms related to this topic - “serving ability”, and “serving capacity”. I’d like to delineate between these, as animal ethics is of high importance to us all, and consideration must be placed upon how either can be achieved. Within the VBBSE, the serving ability component is often not applied, mainly due to the time required for the testing as well as the equipment for heifer restraint.

Serving ability, is best referred to as, “ensuring a bull can mount properly, penetrate and trust to ejaculate semen”. This can be simply done with a cow or heifer in heat. There is no need for restraints, but depending on the amount of bulls to be tested, the amount of females required may not be practical. The relevance of serving ability testing was evident earlier, as in the 8 bulls purchased, one bull was able to mount cows repeatedly, but unable to penetrate and trust to deliver the semen into the vagina. If this bull had been noticed in a paddock mounting without testing, highly likely he would be considered as a high worker, until the pregnancy test results came in at a later date.

Service capacity is “the study of how many times a bull serves over a given period of time”, namely a ten or fifteen minute period. As an example, one service by a bull in this period, would indicate a low capacity bull that could be mated to 25 cows. A bull that served 3 times maybe be a medium capacity bull, capable of covering 50 cows, while a bull serving 5 or more times in that period are regarded as high capacity and capable of covering 75 cows. To conduct this testing, females not cycling are used, and need to be restrained. Therefore, it is rarely utilised and impractical under general circumstances.

With consideration to the above explanations, producers can do simple testing of their own to help ensure their sires are sound. Utilising synthetic prostaglandin, cycle some females of each joining mob for when the bulls first go in. This is a simple way to take a little time to watch your sire serve and for you to be confident he will remain sound post serving. In my experience, it’s just not selling or buying a bull where this information is useful. Results from sire testing by the pastoral company previously mentioned, they identified 2% of their herd sires to have serving issues annually, generally these issues were due to the onset of arthritis. It is important to mention that some of these sires showing arthritic signs, were as young as 3 years old. These younger sires were loosely identified as the ones that had been finished on high grain rations for sales.

There is no exact science of a good bull vs a dud, or which one will have the most profound effect on your breeding - sometimes it is trial and error. Generally, we place a high focus on EBV’s to seek the traits we require to suit our objectives. As for fertility, we just buy a bull and put him out for joining, expecting they will go and do their job. By taking some time to fertility test in line with the VBBSE we can make leaps and bounds on our herd fertility, with the bonus of achieving more calves, and reducing cull cow rates.