Forage Facts

February 2002

In This Issue . . .

     - Planning for Forage Production Needs

     - Charts:  Ag Bag Storage Information

     - Charts:  Bunker/Trench Silo Capacities

     - Charts:  Silo Capacity Chart

     - Charts:  Chopper Box Capacity

When you begin planning for your forage needs, you need to consider your options and the factors that affect your ability to produce and store quality forages. These factors include the amount of land you have available, the fertility of the soil, the supplementation options available to you, and your storage facilities.

There are four questions you must answer:

1. How much forage/feed is needed?

2. Where to store the forage/feed? (land resources, cost per ton of recovered dry matter)

3. Storage capacity – How big?

4. Forage/feed delivery – How to feed the herd efficiently - labor/shrink

The factors that influence your forage needs are the number of cows you are feeding as well as their size and level of production. You can calculate forage needs for heifers as half of that of a mature cow.

• What is the dry matter intake of your cows?

• What percent of intake is forage?  Generally, we use 2 1/2 % of body weight to calculate forage intake.

• What about losses on the farm?  

          Sources of losses:

          - Storage - fermentation, liquid run-off, gases, birds, rats, wind, water,  

              spoilage

          - Feeding

          - Field losses

We have a 100 cow milking herd with 18 dry cows and 8 springing heifers, average body weight of 1400 lbs.

With forage intake at 2 1/2% of total body weight:

= 1400 lbs. x 0.025 = 35 lbs. forage DMI/cow

Estimate total forage intake for herd for the year:

= (35 lbs. x 126 head x 365 days)/2,000

= 805 tons forage dry matter

Lets say you feed a ration consisting of 75% corn silage 25% dry hay:

Corn silage = 805 tons x .75 = 604 tons DM

= 604 tons/.35 = 1725 tons as fed (65% moisture)

Alfalfa hay = 805 tons x .25 = 201 tons DM

= 201 tons/.85 = 236 tons as fed (15% moisture)

To assist you with your forage planning, we have included several charts and tables that list the capacities of various storage methods.

Ag-Bag International - Bag Information

Suggested Feed Out Rates Per Day

                                                  Winter rates (Oct - April)                              Summer rates (May - Sept.)

Capacity of Tons Per Running Foot of Bag

8’      1 ton

9’      1 ¼ tons

10’    1 ½ tons

11’    1 ¾ tons

12'     2 ¼ tons   

 

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Bunker/Trench Silo Capacities

Tons of Wet Forage/Foot of Length*

 

Bottom width (ft.)**

Depth (ft.)	20	30	40	50	60	70	80
8	3.4	5.0	6.5	8.1	10.0	11.3	13.0
10	4.3	6.2	8.4	10.2	12.2	14.2	16.2
12	5.2	7.5	10.0	12.3	14.6	17.0	20.0
14	6.0	8.7	11.5	14.3	17.0	20.0	22.7
16	7.0	10.0	13.1	16.3	20.1	22.7	26.0

*Capacities are based on 70% moisture silage weighing 40 lbs./ft³                                           Source: Cromwell et al. 1989

**Sidewalls slope out 1 ft. in 8 ft. of height

 

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Silo Capacity Chart

Size	Tons of silage at 65% moisture	Size	Tons of silage at 65% moisture	Size	Tons of silage at 65% moisture	Size	Tons of silage at 65% moisture
14x40	123	18x50	274	20x80	700	24x70	823
14x50	171	18x60	365	22x40	312	24x80	1027
14x55	201	18x65	421	22x50	433	26x50	590
16x30	109	18x70	459	22x60	549	26x60	771
16x40	161	20x40	256	22x70	690	26x70	969
16x50	218	20x50	339	22x80	853	26x80	1226
16x60	288	20x60	452	24x50	497	30x60	1037
18x40	206	20x70	568	24x60	651	30x70	1344

 

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Chopper Box Capacity at 65% Moisture

 

                                                                    Wagon Length (8 ft width)

Depth	16 feet	18 feet
4 feet	3.7 tons	4.1 tons
5 feet	4.6 tons	5.2 tons
6 feet	5.5 tons	6.2 tons
7 feet	6.4 tons	7.2 tons