Read this article of Jerry D. Olson, DVM, MS from the University of Minnesota about the correlation between the Rumination rate and the Displaced Abomasal metabolic disease:
Health and Reproductive Aspects of the Pericardium Cow

The Nederland’s, May - June 2003

First hint to upcoming problem can be seen five days before calving with a sudden reducing in Rumination rate on the 30/05/03. Calving on the 03/06/03, second hint we have a day after calving as Rumination rate is still very low, around 200 minutes. Usually Rumination rate dramatically reduced on the calving day only, but not in this case.
Milk production looks normal for the first 2 days, afterwards milk production also reduced for the next 8 days with around 10 Kg a day.
On the 8th Ketosis was found by the vet, cow was treat for Ketosis.
On the 9th there is some improvement in Rumination rate but at the next day Rumination is very low again.
On the 11th we have the first diagnosis of Displaced Abomasums
On the 13th the cow finally had a surgery on the farm.

Rumination rate is dramatically increased soon after the surgery, milk production slowly recovered.

Conclusion:
This Displaced Abomasal case story is typical to the grazing season in the Nederland’s. See how the general herd Rumination rate reduced as the grazing season started, this lack of a real effective fiber indicate the need to add other effective fiber sources to the cows besides the grazing.
Early response according to Rumination pattern of all the grazing cows could prevent
Displaced Abomasal cases.
Early response according to Rumination pattern of the present cow could save days of milk loss.


Health and Reproductive Aspects of the Peripartum Cow
Jerry D. Olson, DVM, MS
University of Minnesota

"Maintaining a functional fiber mat in the rumen is important For the prevention of abomasal displacement. "

The particles of Roughage material should be long enough to stimulate rumination and act as a functional particle trap.

Unfortunately, there is not an easy method for determining the quantity of roughage particles of adequate length to meet the aforementioned functions, especially when the forage is in the form of silage or ground hay.

However, an alternative method for evaluating the adequacy of roughage function can be an indirect method that measures the amount of time a cow spends ruminating. A minimum of 50% of the cows should be chewing their cuds when the cows are not being fed, moved to the milking parlor, or being milked. Cows eating adequate forage will be chew their cuds about 50% of the time where as cows eating inadequate forage will be ruminating less.

An adequate fiber mat can be maintained by feeding some of the roughage as long stem hay or ground hay or silage of adequate quantity and particle length.

The problem is in determining adequacy of quantity and length of Forage particles. Another factor to consider is that the fiber mat is in a dynamic state with new material being continually added and Old material being continually degraded. If the cow goes "off-feed"
For any reason, degradation of the fiber mat will continue to occur. When the cow resumes eating, there may not be a functional fiber mat left and the concentration of VFA's in the rumen effluent will be elevated until the fiber mat is re-established. Until the functional fiber mat is replaced, the cow is at increased risk of abomasal displacement."

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