Question
Hi Eoin
I was recently talking to a dairy farmer who does his own A.I and during the conversation he told me that ,generally speaking angus and belgian blue bulls are the only sires that will ensure that a cow calves on her due date and not carry over for days or in some cases, weeks. Charlaois on the other hand are notorius for the opposite, hence a cow going two weeks over and having a massive calf and a difficult calving. If all this is broadly true, and you want to have charlaois calves all the time but you are afraid of the difficulties involved with the breed,is it possible to induce calving if you know the exact date the cow went in calf, and therefore reduce the risk associated with the breed. Am I being ridiculous?
Reply
Inducing cows to calve early by the injection of steriods and prostaglandins is certainly an option to reduce calving difficulty. There are a number of issues to consider, however, before implementing this as a standard policy with all or most of your cows.
i) Firstly, it must be remembered that all breeds have their own specific range for normal gestational length, i.e. the average length of gestation/pregnancy for the Aberdeen Angus breed is 280 days; the Hereford breed is from 282 days; the Charolais breed is 284-287 days; the Simmental breed is 284 days; the Limousin breed is 287 days. Most of the continental breeds tend to have slightly longer gestation periods of 285 – 290 days (9.5 months approx.). Therefore, it should not be surprising if cows are not calving at 9 months exactly every year – in fact this would be slightly early for most breeds.
ii) There is no doubt that if a cow has a gestation length of >290 days, she will have a larger calf and the risk of calving difficulty rises greatly. However, as long as large terminal sires such as Belgian Blue and Charolais bulls are used on good suckler cows, as opposed to heifers, the majority of calvings will occur without the need for assistance or with minor assistance. Therefore, calves would want to be of high value before deciding to implement a blanket policy of inducing cows with the added financial expenses this would incur.
iii) While on one hand inducing cows to calve early will reduce the risks of calving difficulties and the associated costs (caesarian sections, veterinary fees, increased calf mortality, calving fractures etc.), there are some side-effects to the induction of calving, including: a) increased incidence of retained placenta, b) reduced viability of the calf, especially if induced too early (< 270 days gestation), and c) potentially poor milk production if induced too early (at 260 days or less) – hence the importance of knowing the insemination date. These side-effects, with retained placenta and subsequent uterine infection/metritis being the most common, also have significant economic costs attached to them.
My advice is to tailor the choice of sire to the cow in question, with increased weight placed on reduced calving difficulty in the €urostar index. Do not use the Charolais bull on heifers. I would advocate inducing cows when they have passed 290 days in calf or cows with a previous history of calving difficulty. If there is any doubt in your mind, however, as to the accuracy of your records for insemination dates, definitely contact your veterinary practitoner for reproductive examination so that the cow is not induced too early. Your vet can also advise you on the value of inducing late-calving cows with a view to creating a more compact calving season – my view is that cows can be very successfully induced after 270 days gestation, with reduced incidence of side-effects the closer to 280 days gestation.
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