Proper forage sampling critical to formulation

Proper forage sampling critical to formulation

Proper forage sampling techniques result in having a representative analysis of the feed on the farm and are vital for formulating a balanced ration.

By TAYLOR HOLTERMAN, SCOTT BASCOM and TIM SHERVEN*

ANY number of variables on a dairy farm can affect milk production, but one variable that is commonly overlooked is whether or not the nutritionist formulated the cows' diet using an accurate corn silage sample.

Agri-Nutrition Consulting and Rock River Labs recently teamed up to showcase how poor corn silage sampling techniques will cause significant errors in ration formulation. Specifically, they wanted to determine the exact variation in nutrient analysis from sample to sample across the silage pile.

 

Experimental setup

Samples were taken from a corn silage pile consisting of a uniform variety and similar harvest date. Eleven locations were sampled and composited (Figure 1).

 

Results

Among sampling locations, there was considerable variation in moisture, neutral detergent fiber (NDF), crude protein (CP) and starch (Figures 2-5), so taking a representative sample is vital to getting an accurate forage analysis.

To determine the effect sample variation would have on ration formulation, rations were then formulated using the samples shown in Table 1: a composite sample, the sample with the highest starch content (M2) and the sample with the lowest starch content (T1).

Rations were balanced to support 75 lb. of milk at 3.5% fat-corrected milk for a mature Holstein cow. The ration, along with corn silage, contained soybean meal, high-moisture shell corn (HMSC), mineral and a fixed amount of haylage (Table 2).

As demonstrated in Table 1, the composite and low-starch rations were similar; however, the high-starch ration was considerably different. The high-starch corn silage sample was 57% moisture, compared to 64% in the composite and low-starch samples.

If using the high-starch sample (M2) to develop a ration, corn silage would end up being underfed because that sample was 43% dry matter, yet the actual corn silage dry matter was 36% (Table 3). The formulated ration will be "unbalanced" because the forage analysis used does not accurately represent the nutrient profile of the feed available on the farm.

Keep in mind that cows producing 75 lb. of milk will eat approximately 46 lb. of dry matter per day. Hence, the actual diet the cows would be consuming with a ration formulated based on the high-starch sample would be short on non-forage carbohydrates (NFC) and net energy of lactation (NEL).

As a result, cows would not reach target milk production with such a diet, which would lead to a decrease in income over feed cost compared to feeding a ration balanced with an accurate representative sample of the feed on the farm.

 

Application

Rations formulated based on a forage analysis from poorly sampled forages can be costly. Forage samples that don't represent the feed available on a farm may have a significant negative impact on income over feed cost and herd health.

In order to avoid flawed ration formulation, it is vital to employ proper sampling techniques on the farm. Follow recommendations for taking representative samples from bunker silos and other feed storage structures.

Proper forage sampling techniques result in having a representative analysis of the feed on the farm and are vital for formulating a balanced ration.

*Taylor Holterman is a marketing intern, Dr. Scott Bascom is director of technical services and Tim Sherven is an independent consultant and ration analyst with Agri-Nutrition Consulting. A photo gallery of proper silage sampling techniques is available online from Feedstuffs' sister publication, Hay & Forage Grower, at hayandforage.com.

Proper forage sampling critical to formulation

1. Samples used for example ration

Sample

Description

Moisture

CP

NDF

Starch

pH

T1

Low starch

64.1

7.6

46.9

31.7

4.00

M2

High starch

57.0

6.5

36.8

43.4

4.47

Composite

Actual

64.3

7.3

45.2

33.3

3.87

 

2. Rations to support 75 lb. of milk

 

Composite

Low starch

High starch

 

-Lb. dry matter/head/day-

Corn silage

22.20

21.37

28.30

Haylage

10.00

10.00

10.00

HMSC

7.63

8.59

0.81

Soybean meal (48% CP)

5.94

5.81

6.67

Mineral

1.11

1.12

1.13

 

3. Ration as consumed if sample M2 is used for formulation

 

Actual consumed

Target ration

 

-Lb. dry matter/head/day-

Corn silage

26.2

28.3

Haylage

11.1

10.0

HMSC

0.90

0.81

Soybean meal (48% CP)

7.62

7.43

Mineral

1.26

1.13

Forage NDF, % dry matter

31.6

35.7

NFC, %

33.2

41.3

NEL

0.66

0.69

 

Volume:86 Issue:23

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