Pregnancy testing - what do you want to know???
Apart from more sophisticated scanning equipment and some interest in foetal sexing, it is fair to say that there is little new on the technical front when it comes to pregnancy testing cows. However, it is worth a fresh look at how best to use the information that can come from it.
Historically, for many operators we've progressed from simply deriving pregnant/empty status, to clearly identifying earlies and lates (ie those expected to calve before or after a predetermined date), primarily as a tool to assist wintering decisions or calving induction planning. Either of these two pregnancy testing options may still meet your needs.
Critical management information
As operators subtly shift to management systems that strive to maximize total days in milk and extend lactation lengths, whether in seasonal or biseasonal herds, it is becoming increasingly important to nail down predicted calving dates. This information should strongly drive drying-off decisions, but always needs to be considered alongside cow condition score and feed budget data.
Take the common case of late-July calving cows, dried off in CS 4.0 or less around 20th May or later. Given the energetics of body weight recovery in heavily pregnant cows in the depths of winter, achieving a target CS of 5.0+ by calving for such cows is pie in the sky. Their milking performance, fertility and health will be significantly compromised. An indicative calving date considered along with CS would provide critical detail on which smart drying-off decisions can be made.
Get your timing right
You could rely on what is seen and recorded on farm to generate an expected calving report, but herds with high heat detection efficiency, and therefore reasonably accurate due calving lists, are the exception rather than the rule. For most, properly timed pregnancy testing is a means of confirming conception dates and identifying cows that have held to unobserved returns, or not conceived at all.
Accurate ageing of pregnancies requires early testing. Beyond approx 14 weeks, the pregnant uterus falls over the brim of the pelvis, making accurate palpation or scanning of its contents more problematic.
Having made the decision to pregnancy test early, the optimum time would be SIX weeks after the end of artificial breeding (AB). For most, this would occur in late December through to January. Cows diagnosed in-calf could confidently be expected to calve in a time period equivalent to the length of your AB period. Detail on number of weeks pregnant could be provided for even greater forward planning. The second wave of testing would be timed for the standard 6-8 weeks after the end of mating.
The downside of early pregnancy testing is three-fold:
- Expected ‘normal losses'. The reality is that when pregnancy testing 14 weeks after planned start of mating, an average normal loss from pregnancy testing to calving would be 3.7% (based on extensive NZ survey data). This figure may include for example losses from a grumbling BVD problem, a trace element deficiency etc. In a 300 cow herd this would be 11 cows. A loss of 20 pregnancies in a 300 cow herd can still be considered as the upper end of normal.
- Technically more demanding so takes slightly more time.
- Potentially occurs at a time when summer holidays for you or your team might be high on the agenda.
Early pregnant cows will command a premium this season for next. There will be value in knowing which ones they are - early pregnancy testing is the tool to do it.
Decide what herd pregnancy information you need and discuss the best way to obtain it with your Totally Vets veterinarian. Planning for improved outcomes could start here.
