Autumn Pregnancy Testing
Many farmers now choose to pregnancy test their herds in late spring or early summer. This provides them with a more accurate estimation of stage of pregnancy for their cows. Farmers who do not pregnancy test until late summer or autumn, are well advised to pregnancy test their herd as soon as possible.As pregnancy becomes more advanced the ability to accurately age the pregnancy deteriorates. The result of this will be that we can not consistently differentiate whether a cow is in calf to AI or the bull hence, it will not be possible to supply expected calving dates accurate enough to dry early calving cows off for a seven to eight week dry period.
By waiting until March or April when the early calvers are only two months from calving, our estimates can be out by six weeks or more on some cows due to the large variation that occurs in uterine and foetal development at this stage. It is necessary to dry these cows off to their AI dates. Some cows will have a longer spell because they have conceived to a bull mating three to six weeks after their last AI. This is unfortunate, but less of a problem than having cows calve earlier than expected.
Earlier pregnancy testing will also permit a more accurate identification of the cows to be induced and their anticipated induction date can be arranged. If these cows, which are August to October calvers are pregnancy tested in mid February, they will be six to sixteen weeks in calf. If they are not pregnancy tested until late March, at 12 to 22 weeks, it is much more difficult for us to be accurate with their estimated calving date.
If bulls are left with the herd through January or February there will be a handful of pregnant cows undetectable at a February pregnancy test. These will be late October-November calvers and most cases will be culled. Younger cows in this group that could be kept and induced can be rechecked in April or May.
Click here to view the rest of the 1999 February newsletter.