Pregnancy Scanning

There are four main reasons why you may choose to pregnancy test your herd early:

Firstly: if you have used CIDRs and have got a suspiciously high non-return rate then a pregnancy test at day 50 or thereabouts after mating will confirm pregnancy or otherwise to that mating.

Secondly: If early embryonic loss is suspected or long returns are occurring then pregnancy testing will give you information in good time so that you may be able to do something about it. This may involve mineral checks, BVD status, manual palpation If ovaries etc.

Thirdly: To define your conception date where records are poor or non-existent, or simply to confirm conception at recorded date, or that it is an AI conception. This testing is done 12 weeks after the planned start of mating (PSM). You cannot accurately date pregnancies over 12 weeks.

Fourthly: It is a legal requirement that cows that are to be induced must be between 12 and 6 weeks away from calving. An accurate conception date must be known and the most practical time to test in this case is 18 weeks after the PSM.

The end of season scanning is done 6 weeks after the bull is removed from the herd.

There are limitations to scanning. Carryover cows are very difficult to scan, usually because they are very fat and there is limited movement in the colon, so these are best done manually.

Cows that are over 5 months pregnant generally are difficult to detect because the uterus drops down into the abdomen out of reach of the probe.

Cows should not have gorged on crops immediately before scanning.

In some cases the pregnancy is off to one side where the probe cannot reach and manual checking is necessary.

Our setup is self contained. We have a battery operated unit with a heads-up display, so we do not require a power source and we are not limited to a fixed monitor. We have a dairy caddy which allows us to move in the pit of a herringbone shed, provided the floor of the pit is smooth, without obstructions and access to the cows rear ends are not obstructed by droppers or milk lines etc.

All cows with no detectable pregnancy on the scanner are re-checked manually at the end of season scanning. On very early scannings, this is not done as a significant proportion of cows are not pregnant or not detectably pregnant manually anyway.

In other situations, it is important the cow is suitably restrained and that we have safe and easy access to the cow. Carrying an expensive scanner on our backs does impair our mobility. An expensive and fragile probe can also be difficult to maneuver.

Early scanning, and particularly if we are dating pregnancies, can take a while. We are generally able to do 50-80 cows per hour.

It would be a help if you have records, so that we can confirm dates. It does make it quicker. The procedure also requires labour. People are needed to move the cows and also to record the information. This person recording should have knowledge of the cows and their expected mating performance.

There are some risks to scanning. In particular there is a danger the probe can penetrate the colon leading in most cases to fatal peritonitis. Whilst, to our knowledge, this has never happened to us, where it has happened to scanners – they have commentated that they felt nothing unusual.

It is important to introduce the concept of gentleness and patience. Often the insertion of the probe will induce a peristaltic wave which pushes the probe back out again. Scanners must allow this to happen which takes time and patience. You have to wait for the bowel to relax again before trying again so bear with us! The aim is to pregnancy test the cows – not kill them!

Finally there is the concept of embryonic loss.

In general if you take 100 cows and mate them then in 90 of them the sperm and egg will meet and produce an embryo. In 13 days time, only about 70 embryo’s will implant or attach to the uterus. Uterine infection or inflammation or scarring prevents the rest from implanting. Other diseases, mineral deficiencies, stress and hormonal imbalances can cause further losses.

These are statistical figures and obviously if you have initiated procedures such as metrichecking your herd and treated affected cows, the probability of conception and embryo survival is increased.

But again, statistically, research figures suggest that 1.5% of cows with 49 day pregnancies will lose them in the next two weeks.

Similarly 0.3% of cows with 15 week pregnancies will lost them in the following two weeks. Some of these losses can be explained by disease but a good proportion occur in the absence of any diagnosed disease.

It is postulated that the embryo is genetically aberrant and dies. A similar situation occurs in humans.

There may be up to 3% losses between end of season scanning in March-April and drying off in late May. As a result in past seasons some large herds have also scanned at drying off as the cost of over wintering these cows exceeds the cost of pregnancy testing.