How Long Does A Cow Need For Her Dry Period?
Gone are the days for many farmers where it is possible to dry off the whole herd for 2 months and have a break from milking. The tight financial situation for such farmers means that cows need to be producing as much milk in autumn as possible to help produce any profit for the year.Apart from that reason, some farmers will choose to milk through because they can make more money during the high paying months of March to June. Building up a feed wedge for winter can still be achieved simply by slowing the rotation if necessary and continuing to feed supplements to the milkers such as silage hay and grain.
A cow still producing 18 litres in April will need about 6-8 kg dry matter more than she would if dry. If this were all as grain, it would cost an additional $1.20 in feed costs per day to keep her milking. At 30c/litre x 18 litres this is $5.40 per day giving a net profit per cow of $4.20.
The milking and shed costs need to be taken into consideration, however, if a relief milker is needed whilst having a well earned rest, it is easy to show a substantial economic benefit from keeping cows milking rather than drying them off.
Cows need an optimum 7 weeks for the udder to be spelled long enough to then be able to commence another lactation unhindered from the previous one. Once the spell is less than 6 weeks, her production in the new lactation will start to be affected. A dry period of longer than 7 weeks may help her to put on condition but will be of no extra benefit to the udder. About 10% of cows will calve up to a week early and a small number will calve more than a week before they are due. In the past farmers have chosen to give cows 8 weeks or more which allows these cows to have at least 7 weeks spell. This practice gives most cows a 9-10 week break because they are usually dried off in batches every 2-3 weeks, the earliest calvers having at least 8 weeks. If cows are dried off once weekly, this will shorten the dry period for many cows in the herd.
Cows that are 49-56 days from their expected calving date will average 52 days and very few will calve more than 10 days early giving them less than 6 weeks. The trend today is to have cows in the condition score required for calving at drying off. It is difficult to put condition score on cows in the dry period unless they have a long spell or seasonal conditions are favourable.
It is only possible to carry out this dry cow program if anticipated calving dates are reasonably accurate. Herds where diligent heat detection has occurred for most of the joining period or where early pregnancy testing (before Christmas) has occurred, the predicted calving dates should be reliable. The later the cows are due, the more likely that heat recording will be inaccurate. Usually heats are missed so cows will calve later than expected. Too diligent heat detection will result in some cows being recorded to false heats who subsequently calve to an earlier service. The whole herd would need to be dried off at least 6 weeks before calving to avoid such an occurrence.
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