Pregnancy testing is a great opportunity to gather information about the success of your mating programme and to plan for the management of cows around calving. Using accurately dated pregnancies, you can establish your 6 or 8 week “In Calf Rate”. This is by far the best measure of reproductive performance of your herd – talking about “empty rate” really only indicates how late you left the bull out, and how many inductions you are prepared to do! The higher your 6 week ICR, the more compact and efficient your calving will be, the more days in milk you will get, and the more successful the next mating will be.
Some farmers like to identify cows into fortnightly calving groups to bring home from run offs and feed into the springer mob. Others like a distinction made between AI and bull mating calves. Inductions for the management of late calving cows will be available until the “Code” governing their use is reviewed in 2009. Pregnancy testing is the time to identify which cows to induce and when.
We can accurately age pregnancies from 30 days post conception to about 84 days. However young pregnancies can be missed (especially with a scanner) and there is a high rate of embryonic loss up until about 6 weeks. For these reasons we don’t like to confirm any pregnancy much less than about 40days, and a cow can’t be definitively called “empty” if she’s had contact with a bull within the last 6 weeks. It is inaccurate to be sorting calves into groups by age any more than 12 weeks after the mating date.
The best time to pregnancy test is therefore about 6-10 weeks after the mating date for the cut-off you want to identify:
8-12 weeks after PSM
6-10 weeks after end of AI
6 week ICR
12-16 weeks after PSM
6-10 weeks after last natural calvers mated
6 weeks after last bull contact.
At pregnancy testing time, make sure all results are clearly recorded against tag numbers on paper (and remember to put this years date on it!). Make a copy, and keep one at the cow shed, and one at the house.
Of course, Clutha Vets are happy to tailor a pregnancy testing programme and do all of this with you. We can then use MINDA mating records, or our own computer program, to generate lists of which cows are which. Please speak to a vet now to sort out how you can use pregnancy testing as a powerful tool in your farm management. Don’t just ask for “Pregnant”, “Late” and “Dry”.
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