Effects of Feeding Spoiled Corn Silage on Intake and Digestibility

Dr. Ronald L. Boman
USU Extension Dairy Specialist

I was recently privileged to attend a seminar on �Important Factors Often Overlooked in Forage Management� given by Dr. Keith Bolsen of Kansas State University. This very practical and informative presentation was sponsored by Intermountain Farmers Association of Utah and they are to be congratulated for arranging such an outstanding seminar. I picked up the following five (5) points from Dr. Bolsen�s presentation:

  1. Innoculate the silage-- use lactic acid cultures of 100,000 cfu/gram of silage;
  2. Pack the silage-- use enough single wheel weighted tractors and pack in 6 to 12 inch layers;
  3. Cover the bunker-- use plastic (6 mil) weighted with used tires (or something better if you know of it) to exclude air and water;
  4. Manage the feed-out face-- by keeping the surface smooth and perpendicular and remove enough each day to keep spoilage down; and
  5. Pitch the spoilage-- remove the spoiled material and feed only well preserved and good quality silage.
I want to expand on the fifth point. I see too many dairy operations where the spoiled silage on the top and the sides of the bunker (or even in Ag Bags where the plastic has been punctured) is being mixed with the �good corn silage� and included in the TMR. Dr. Bolsen cited research in which 0, 25, 50, and 75% spoiled material (from the original top three feet of uncovered bunkers) was purposely included in the total corn silage in the diet of rumen fistulated steers. Steers were fed 90% of their dry matter as corn silage and 10% as supplement. I will only report on the 0 and 25% levels of spoilage, because most dairies would not exceed the 25% level. Table 1 shows the difference in intake and digestibility of the normal corn silage ration compared to one in which 25% of the corn silage came from the original top three feet of spoiled material. Notice the lower intake of dry matter and lower digestibility for the diet containing the spoiled corn silage.

Table 1. Effect of level of spoilage on intake and nutrient digestibility of steers fed corn silage.
Normal Corn Silage 25% Spoiled Corn Silage
Dry Matter Intake (lb/day) 17.5 16.2
Digestibility (%):
Dry Matter 74.4 68.9
Organic Matter 75.6 70.6
Crude Protein 74.6 70.5
Neutral Detergent Fiber 63.2 56.0
Acid Detergent Fiber 56.1 46.2
Source: L.A. Whitlock et al., Kansas State University Dairy Days 2000. Manhatten, Kansas.

The addition of surface-spoiled corn silage had a statistically significant negative effect on dry matter intake and all of the digestibilities that were measured. IN ADDITION, WHEN THE RUMEN CONTENTS WERE EVACUATED, THE �FORAGE MAT� WAS PARTIALLY DESTROYED IN THOSE STEERS RECEIVING A PORTION OF THEIR DIETS AS SPOILED SILAGE. The �forage mat� is important to normal rumen motility (contractions). When rumen motility is adversely affected, the rumen microbes suffer, and passage rate and nutrient absorption decline. Some researchers have suggested that spoiled silage may be one of the contributing causes of lowered butter fat. Covering corn silage bunkers with plastic and weighting the plastic with used tires or other material isn�t rocket science, but according to Dr. Keith Bolsen there are few other effective alternatives. Spoiled silage can occur even in the best packed and covered corn silage, and it behooves us to take the time and effort to �pitch the spoilage� so that we don�t adversely affect the dry matter intake (palatability) and the digestibility and nutrient utilization of the rations we feed our dairy cows and heifers. ©