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STOCK VET VOICE
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internal pelvis, and a prominent pubic symp They may have a body shape more like a ste If you are synchronising your heifers, you ar progesterone-releasing device in very far, c At pregnancy scanning, it is typically hard to small and underdeveloped
Image 1: Twin heifer calves may be retained as repl
Twinning and Freemartins Words by: Lisa Whitfield
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aving just come in from calving tangled twins on a local dairy farm, it became clear that twins are generally considered problematic for many dairy farmers. While some farms love them, and will keep live twin heifers as a novelty in the herd, others don’t keep any twins, to try and reduce the incidence of twinning in the herd. Twinning is not all that common in dairy cattle – and it seems to vary widely by farm. I have heard reports of up to 10% of a herd having twin calvings. Anecdotally, from farms I have worked with, it seems that the number would probably sit between 1 and 2% of calvings each year. There is no readily available data on twinning rates for the New Zealand dairy herd. I have seen the amount of extra work it can create in springtime when there are more calves born than cows which have obviously calved.
Did you know that with the right timing and the right ultrasound machine, twins can be identified relatively easily at scanning? Going through the springer mob with a fine tooth comb to Twin heifer calves may be retained as replacements. make sure a cow isn’t missed adds a lot of time to days which are already full. If you are lucky, you have enough breed variations and good records, which allow you to narrow down the pool of cows a mystery calf could or two if you know which cows definitely have twins have come from. I don’t envy people with purebred when it comes around to calving time. The ideal time herds having to figure out which cow had twins. to identify twins is when a pregnancy is less than 90 Twins also makes the dam more likely to have days old. The use of a curvilinear scanner by the person calving trouble, and reproductive problems postscanning also improves the likelihood, as this gives a calving. deeper and wider field of view into the uterus (22cm), Lisa Whitfield The most common problem calving presentations I see compared to the traditional linear scanners used (12-15cm). when twins are involved is the first calf being in Freemartins are one of the big headaches associated with twins breech position so needing assistance, or the calves being tangled it seems. A freemartin refers to the female twin which is born to up with each other. Did you know that with the right timing and the same pregnancy as a male calf. In over 90% of cases these the right ultrasound machine, twins can be identified relatively female calves are infertile. easily at scanning? It does take a few extra seconds per cow to Shared blood supply between the calves results in abnormal check at scanning, but even if not all twins are identified, it is development of the reproductive organs, primarily of the female useful to know of as many as possible and may save a headache calf. Many people keep freemartins for the freezer, however, 78
Dairy Exporter | www.nzfarmlife.co.nz | September 2021
