Expert Answers - May 16, 2008

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Answer provided by Keith Bolsen, professor emeritus at Kansas State University and a well-known silage expert, and Ruthie Bolsen, managing director of Keith Bolsen & Associates in Austin, Texas.


Q: What should dairy producers do with surface-spoiled corn silage: feed it or pitch it?

A: There will be an estimated 14 to 18 million tons of corn silage within the top 3 feet in bunker silos and drive-over piles this year. Unfortunately, not all corn silage is sealed and not all seals are effective.

Results from a Kansas State University trial that determined the effect of feeding surface-spoiled, "slime" corn silage on DM intake and nutrient digestibility are shown in Table 1. The original top 3 feet of corn silage in a bunker silo was not sealed for 90 days and allowed to deteriorate. The original top 18-inch layer was visually typical of an unsealed layer of silage that had undergone several months of exposure to air and rainfall. It had a foul odor, black color, and mud-like,"‘slime" texture. This extensive deterioration produced very high pH, ash, and fiber values. The original bottom 18-inch layer had an aroma and appearance associated with wet, high-acid corn silages, i.e., a bright yellow color, low pH, and very strong acetic acid smell.

The surface-spoilage was fed to steers fitted with ruminal cannulas. The four experimental rations contained 90 percent corn silage and 10 percent supplement (DM basis), and the proportions of silage fed were: A) 100 percent normal, B) 75 percent normal/25 percent spoiled; C) 50 percent normal/50 percent spoiled, and D) 25 percent normal/75 percent spoiled. The proportion of the original top 18-inch and bottom 18-inch spoilage layers in the composite surface-spoiled silage was 24 and 76 percent, respectively.

Results showed that surface-spoiled ‘slime’ corn silage depressed DM intake, destroyed the forage mat in the rumen, and significantly reduced organic matter (OM) and neutral detergent fiber (NDF) digestibility.

Table 1. Effect of surface-spoiled, slime corn silage on DM intake and nutrient digestibility

Percent of the surface spoilage ‘slime’ in the ration (DM basis) in parenthesis.

 
Ration

 Item

 A (0)

 B (5.4)

 C (10.7)

 D (16.0)

DM intake, lb per day

17.5

16.2

15.3

14.7

 OM digestibility

75.6

70.6

69.0

67.8

NDF digestibility

63.2

56.0

52.5

52.3

The predicted combined effects of silage management and feeding practices that are associated with creating and feeding surface-spoiled, ‘slime’ corn silage to growing cattle are presented in Table 2. Surface spoilage decreased the net value of liveweight gain from about $3 to over $26 per ton of crop ensiled.

Table 2. Predicted economic impact of feeding ‘slime’ corn silage to growing cattle1

 
Combination

 Item

 A

 B

 C

 D

Surface-spoiled ‘slime’ in the ration, % on a DM basis

 0

 2.7

 2.7

 5.4

Corn silage NEg, Mcal per lb of DM

0.45

0.45

0.425

0.40

DM recovery, % of the crop ensiled

87.5

87.5

82.5

77.5

DM intake, lb per day

17.00

16.50

16.50

16.00

Avg. daily gain, lb

2.25

2.12

2.00

1.75

DM per lb of gain, lb

7.55

7.80

8.25

9.15

 2Silage per lb of gain, lb as-fed

19.85

20.5

21.65

24.05

Gain per ton of crop ensiled, lb

88.2

85.4

76.2

64.4

Lost gain per ton of crop ensiled, lb

---

2.8

12.0

23.8

 3Value of lost gain per ton of crop ensiled, $

---

3.08

13.20

26.18

1 From data from Whitlock et al. (2000). 2 The corn silage is 33.3 percent DM. 3Liveweight gain was $1.10 per pound.

The KSU research showed that each 1 percent surface-spoiled, ‘slime’ corn silage in the ration could decrease NDF digestibility by 1.3 percentage units. Michigan State University reported that 1 percentage unit of NDF digestibility equals 0.55 lbs of milk per cow per day. Thus, 1 percent surface-spoiled, ‘slime’ in a ration could decrease milk production by about 0.7 lbs per cow per day. This is about $38 per cow per year, when milk is $18 per hundredweight. In poorly managed bunker silos and piles, it is possible for a feeder to consistently put 1 to 2.5 percent ‘slime’ in a ration. This could decrease milk production by about 1.5 to 2 lbs per cow per day.

Bottom line: Now is a good time for dairy producers to discuss with everyone on their “feeding team” the importance of keeping surface-spoiled corn silage out of every ration every day!!



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