A “fall slump” in milk production is a common occurrence on many dairy farms. It is characterized by some or all of the following: a moderate to large decrease in milk production, a decrease in intake, loose manure and cycling intakes.
Fall slumps are often a result of feeding corn silage that has not had adequate time to complete the fermentation process. Depending on the specific crop and conditions, most silages require three to six weeks before the fermentation process is complete.
The fall slump may occur because fresh corn forage contains high levels of fermentable sugars that can put the rumen into sub-acute acidosis. The condition occurs most with corn silage because it is usually the highest proportion of forage fed in the diet.
Fall slumps are most apparent when cows are switched abruptly from old corn silage to freshly cut corn forage. This occurs frequently on small farms that have only one silo for corn silage.
A fall slump may also occur when switching from one corn silage to another because the new year’s silage may be lower in nutritive value. Not accounting for differences in the dry matter and nutrient content of the new silage when changing silos can certainly cause problems.
Several approaches can be taken to minimize the incidences of a fall slump. First, for those dairymen that have adequate forage inventory and silos, plan to allow new corn silage to ensile for at least two to three months before feeding.
Next, when switching from one silo to another, try to make the change gradually over a minimum of a 10- to 14-day period. This is obviously very difficult to do if you only have one silo.
For this reason, a case could be made to encourage farmers with only one main silo for corn silage to also put up a small bag (or drive-over pile) of corn silage every year that can be mixed with new silage and fed out during the fall.
Last but not least, new forages should be tested for dry matter and nutrient content and diet formulations should be adjusted accordingly. PD
—Excerpts from University of Delaware Kent County Agricultural Extension blog, September 2009
Limin Kung
Animal Sciences
University of Delaware
lksilage@udel.edu
