'The Art' of farm pregnancy testing

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Pregnancy Testing is an important event to schedule into the management calendar.  Depending on whether the enterprise is geared for dairy or beef production, there are differences in timing and use, but the aim is the same - determination of pregnancy. 

In a beef unit, pregnancy testing provides useful information that will impact management for the rest of the year.  If one distinct calving season is desired, any cows not in calf after mating can be culled.  If a separate group calving is manageable, empties (cows not in calf) may be returned to the bull and tested later.  Culling empties will increase herd fertility (by eliminating animals that are not able to get in calf within the timeframes desired).  This then has an additional benefit with respect to feeding – feedstuffs (both on pasture and bought in) can be in limited supply – there is no point in feeding empty cows, or carrying round those older individuals that hang on by getting in calf every other year! 

If all that is needed is a ‘yes’ or ‘no’, then cows can be tested from around 8 weeks post mating, right through to calving!  Accuracy in determining the stage of pregnancy drops the further in calf they are, but often this is not an issue – simply knowing if an animal is calf of not is a very powerful tool.  Very fat animals may be hard to test, and also may have problems calving, so keep an eye on body condition.

On a dairy, pregnancy testing is routine.  Having accurate calving dates enables and promotes more complete management throughout the rest of the year.  Dry periods and lead feeding are much more use if the calving date is known!  For optimal accuracy, cows should be tested from 6-16 weeks post mating.  Stage of pregnancy at the 6-9 week interval can be predicted to within 1 week, and at 9-16 weeks to within 2 weeks.  After this time, as the pregnancy develops, uterine access and foetal growth/size variation become issues in making an accurate estimate of age of the foetus.  Hence testing a 20-week cow may mean a missed lead feed or shortened dry period.  In reality dairy cows should be first tested 6-8 weeks after mating, which will allow time for empties to return to mating without drawing out the calving interval too much. 

Pregnancy testing will obviously identify empty cows.  Depending on the issue these may need treatment (non cycling, polycystic ovaries etc), or simply need further matings.  Problems with the reproductive tract can only be confirmed with an internal examination, so the test is useful for empty cows too!

Issues, such as bull problems, involved with service, be that artificial insemination or natural mating, will be picked up by prompt pregnancy testing – higher than normal empties can prompt investigation.  Infectious diseases, nutrition, and various other husbandry and management issues may come to light with a lower than normal conception rate.

As has been mentioned in previous updates and newsletters, bull management and bull pre-mating checks form a key part of herd reproductive management.