Farm Animal Vets - Endell Veterinary Group

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Bull and ram fertility testing

For many years we have tested bulls’ fertility with an artificial vagina, but this requires the presence of a female animal in heat, is time consuming and poses a risk to those who handle the bull. Consequently, the service has not been used very often.

Keeping a defective bull or ram can be a costly business. Figures from the SAC show that the average cost of keeping a bull is about £1000 per year. Large studies into bull and ram fertility have shown that about three in ten are defective.

Infertile bulls and rams are rare, but in 2004 we found two infertile bulls in two small suckler herds. At one PD session none of the twenty-five cows presented were pregnant, and at the other only two out of thirty females were pregnant. In both instances it was too late to turn a new bull out to get the animals calving in the spring/summer.

It can be very difficult to identify an infertile bull, particularly on farms where several bulls are kept and there is no accurate recording of which animals have been running with which bull at what time, but finding a sub-fertile bull or ram can be even more of a challenge.

A sub-fertile bull or ram will get some animals pregnant, but it will take several services and therefore more time. As most people calve their animals only in the spring or the autumn, the consequence of a sub-fertile bull is more empty females at the end of the breeding season. A sub-fertile bull will also lead to a spread out calving pattern. This is not only a nuisance, as pregnant animals need to be checked longer (which has an impact on labour costs), but it will also lead to a variation in the age of the calves, which will have an impact on calf health. Calf scour pathogens, for instance, need time to build up. Therefore, calf scour is normally a problem at the end of the calving season, but the longer the calving season, the worse the problems. A variation in calf ages can also result in an increased risk of pneumonia as older calves carry and spread pathogens to which they are immune to younger and more susceptible animals.

Therefore, sub-fertile bulls and rams are just as much of a nuisance as infertile bulls and rams. They cost money and create a health risk, and should therefore be identified.

The Electroejaculator

Since late 2004, we have been using an electroejaculator to test bulls’ semen. It is a sophisticated version of the one we use to test rams with. Unlike the old ram probe, the new electroejaculator stimulates more accurately the internal male sex glands and has less effect on the nerves of the hind legs. We have bought a special ram probe as well so we can now also test rams with it. As bulls can be tested in a crush, it is a very safe (for human and animal), quick and easy way to test a bull’s fertility.

The Procedure

When the bull is entering the crush, his gait inspected. His feet are inspected when in the crush. He gets a full clinical examination of external and internal sexual organs and the size of the testicles is measured. This reflects directly on the quantity of the semen. After manual stimulation of the internal sexual organs, a probe is inserted and gentle electro-stimulation is applied until ejaculation.

The semen is scored for volume, concentration and contamination before being examined under a microscope. All this takes place on-farm. Under the microscope, the sample is examined for gross motility and motility of individual sperm cells. A sample of the sperm cells is stained and back at the surgery the morphology of 100 sperm cells will be examined.

Our Initial Findings

Semen is extremely sensitive to cold shock. Consequently semen testing cannot be done in poor weather conditions because it could lead to poor semen motility and tertiary abnormalities of morphology (high numbers of loose heads and bent tails).

As most of our progressive beef suckler clients have had their bulls tested and we have tested the first few sweeper bulls in dairies, we have examined over seventy bulls already. We have seen a range of abnormalities: scrotal hernia, testicular deformation, small testicles, “broken penis” and, of course, reduced ability to mate due to lameness. The semen showed: contamination with urine and pus(!), deformed sperm cells (a wide variation), but the most common abnormality of semen was poor motility, ie: less than 30% of sperm cells with a forward progression.

Most, if not all, bulls were re-tested before a negative advice was given. The bulls that were condemned ranged in age from eighteen months to twelve years. Some were after a pre or post sale check, others had been on the farm for many years. Some bulls were tested following poor PD results, but by far the most were routine tests.

It has become clear that an annual bull fertility check can be very beneficial, as bulls can become sub-fertile at a later age. Most farms spend a lot of time and money checking their cows’ fertility, so why not also pay attention to their bulls’ fertility, which is equally vital?

Ram Testing

An often forgotten, but vital component of all flocks are the rams. If undetected, an infertile or sub-fertile ram can have a significant effect on lambing percentages and overall flock profitability. We would therefore recommend that all rams, but particularly new additions to the flock are examined at least 2 months prior to tupping, to ensure that they are fit for purpose. This gives enough time for replacements to be sought if any rams are found to be inadequate.

The fertility of a ram can be relatively reliably assessed by physical examination alone. Fertility examination includes gross examination of the testicles (including measurement of scrotal circumference), scrotum and penis. The rams are also checked to ensure they have no lameness or other abnormalities or disease that would affect their ability to service the ewes. At Endell’s we have the equipment to perform electro ejaculation for semen collection. This can be used to further assess any ram found to have abnormalities on gross examination. Semen is examined for volume, colour and consistency as well as for the motility of the sperm and any microscopic abnormalities.