Giving cows a 60 day dry period is standard operating procedure all around the world. Research studies performed 35 years ago showed that no dry period reduced milk production in the next lactation by 18 to 29%. This research was accepted by dairymen and so the 60 day dry period has become common practice.

I was involved in a research study 30 years ago that gave half the cows a short dry period (30 days) and half the cows a long dry period (60 days). The results showed that the short dry period only reduced milk production a small amount during year one. However, a second dry period significantly decreased milk production during year two.

The concept of 305 days milking and 60 days dry has been the standard for many years. There were seasonal demands for milk and milk products so calving cows every 365 days was profitable. Today our cows give much more milk so we have a much different kind of animal. It is time to test the length of dry period again using our high production cows of the 21^st Century.

Two large dairies and one smaller dairy in Western USA have been experimenting with no dry period verses a 60 day dry period. The experiment is still in progress but preliminary results are very surprising.

The experiment was designed to look at net profit between cows and heifers milked with a conventional 60 day dry period verses those milked continuously with no dry period. Total input costs of feed and labor are being compared to total milk income. Several heifer groups verses cow groups are involved in the study at each of the three dairies.

The research is showing that both milk production and net profit significantly decrease when heifers do not receive a 60 day dry period. When they looked at the results for mature cows, they found exact opposite results.

Mature cows did show a mild decrease in milk production when they were milked continuously with no dry period. However, the milk made during the dry period has more than made up for the loss. The total net income for mature cows with no dry period has averaged $170 more per cow per year. These results strongly indicate that we should continue to examine the profitability of continuously milking mature cows.

The research also reported preliminary results for selected health parameters. They were as follows:

1)	Continuously milked mature cows had the lowest culling rate of any group.
2)	Continuously milked mature cows had no difference in dystocia or calf mortality.
3)	Not one continuously milked mature cow had been culled by mid-October for mastitis
4)	Rebreeding conception rates for continuously milked mature cows has been 55% compared to 26 percent for the 60 day dry period groups.

Comments by Dr. Whitmore.

I was happy to see someone take a close look at the profitability of the dry period. These results are only preliminary so we need to look at the final results at a later time.

It is interesting that they observed less mastitis in the continuously milked mature cow group. Wow! Less mastitis and $170 more profit are too good to ignore. I am thinking of trying this on 10 cows. Maybe you can get your clients to try this on a few cows.

I am sure we would need to use frozen colostrum for the continuously milked new born calves. Large dairies may have adequate fresh colostrum for these calves. I will let you know our results if we try this program on Hill Top cows. Remember that it has a negative effect on first calf heifers.

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