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Compact calving is key

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Compact calving is key

Cows in spring calving herds should be back in calf by now, writes Brian Hughes, Teagasc Advisor, Swinford. Cows that are bred about now will be due to calve in the last days of April or the early days of May. Once calving extends into May it can hardly be described as spring calving.
Calving target
In most herds there will be a few tail-enders but these should not be more than a few percent of the herd. Our target for the calving season is to have 90% of calving within an eight to ten-week period.
 How does your herd perform in this regard and have you got the necessary records to calculate calving spread? Breeding charts are available from Teagasc offices on which all the necessary information can be recorded to enable you to calculate the most significant measures of breeding performance. Sometimes it is said that compact calving is not important and instead calving interval is the crucial measure of breeding performance, ie once each cow has a calf within a 12-month period it doesn’t matter so much when the calf is born.
While calving interval is important I think it is likely that where there is a very wide calving spread the calving interval is also poor, ie much longer than 12 months between calvings.
There is a trend in larger herds where there is spring and autumn calving to let the late spring calvers run into an autumn calving herd and let the late autumn calvers become spring calvers. While this may be a convenient way of holding on to good cows it certainly results in a calving interval well over 12 months and probably around 14–15 months.
Management
Compact calving is an indicator of good herd management and good discipline in other areas. In itself it also produces an even group of calvers that can be managed uniformly. This can give better average performance in that a uniform group have similar requirements in feed, management and parasite control. For example, in relation to group grazing or creep meal feeding, a group of four-month-old calves are more easily managed than a group ranging in ages from two to seven months.
Similarly, when it comes to sale, an even group of calves are more attractive. Where all weanlings are sold in the autumn at the end of the grazing season, it’s the few late born calves that fetch the poorer price and reduces the average group price.
Remove the bull
In order to keep calving compact, the bull can only be left with the herd at the most for 12 weeks. To have a cut of date to spring calving of May 1 the bull should be removed about now.
Another reason to remove the stock bull is to avoid weanling heifers getting in calf. With a big increase in heifer exports to Spain, it is bad for the reputation of Irish weanlings to discover a proportion of them in-calf.
Scanning
Scanning can be used to identify cows that are not pregnant and allow an early decision on whether to keep them in spring calving. Breed them for autumn calving or finish them for sale. If stocking rates are close to extensification limits, early sale of culls can be enough to keep within limits for the last few census dates.
Scanning can be done at about 30 days after breeding which in the case of AI can be determined accurately. If a bull is running with the cows you have to wait until at least day 28 after bull removal to ensure scanning can detect all pregnancies. The procedure will also identify cows carrying twins, which can be given extra feed pre-calving and special supervision at calving.