Early pregnancy testing of dairy herds

Once the rush of the last few months has started to subside it’s time to think about how successful the season has been.

The mating period that we are currently in will set the scene for the next season (or two) in how the cows are going to calve down and what the requirements will be, i.e. labour, feed, milk in the vat etc.

How we determine this and get a handle on what will happen next year is through scanning the cows to determine how far in calf they are. This can be a bit of an afterthought so it’s worthwhile thinking about it now as the earlier we scan then the more accurate we can be. If we are scanning more than 14 weeks after the start of the mating period, then the early calvers can only really be called “well in calf”.

If we are looking for more detailed results then we need to start early, from around six weeks after the start of mating. This also gives us the ability to pick up those cows that have cycled and then gone quiet (“phantom cows”).

The earlier we pregnancy test (PD) relative to the first three weeks of mating can allow for additional inputs to non-pregnant cows if needed, conversely, the later we PD the less information we can give. If we PD at drying off for example it’s simply a case of yes or no.

The benefits of early pregnancy testing include:

  • Ability to intervene with phantom cows that have gone quiet (if testing early after the first three weeks of artificial breeding (AB)).
  • More accurate calving dates and prediction of your calving pattern with entry into Minda directly through Infovet.
  • Ability to split the herd depending on calving date (springer mob formation, off-farm grazing for late calving cows).
  • Assessing the effectiveness of your non-cycler treatment programmes.
  • Accurate estimation of conception rates and assessing AB performance.
  • Determining appropriate bull power and bull out date (depending on number of cows pregnant to AB).
  • Cows that are ‘not detectably pregnant’ or late calving may be identified promptly and culled or sold. This is especially important in years where feed may be in short supply.
  • Better feed budgeting, labour allocation and nutrition planning, based on predicted calving dates.

Often when we talk of early PD, we will look to do two rounds of testing, one six weeks after AB period and then again six weeks after the bull has been taken out. It is worthwhile noting here that if only the Empty/Rechecks at the first round are tested at the second round, some of the early cows to get in calf may slip and return as empty later in the season - or having slipped early will get caught by the bull and then calve late unless rechecked at the second round of testing.

Single rounds of pregnancy testing six weeks after the bull comes are out a good way of determining if the cows are pregnant or not, but it does make the aging of pregnancies less accurate due to the tendency of the foetus to drop down into the abdomen as it enlarges. As a result, this makes it harder to get the scanner positioned correctly (across the skull) in order to accurately age the foetus.

Please feel free to contact your veterinarian to discuss any questions you may have around early pregnancy testing and what it could mean for you.

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