2012 Field Project: Impact of spring weather on alfalfa quality – week of May 14th sample results

MSU Extension has coordinated a short-term field project to collect data to examine the unusual weather's effect on alfalfa quality.

The measure of fiber most commonly used to balance diets of lactating dairy cows is neutral detergent fiber (NDF). The optimum concentration of NDF for alfalfa fed to lactating dairy cows is 40 percent. Alfalfa containing 40 percent NDF allows reasonable grain concentrations in the diet while maintaining adequate NDF concentrations. Research at Michigan State University (MSU) demonstrated that both GDD (growing degree days, base 41 degrees Fahrenheit) and PEAQ (predictive equations for alfalfa quality) provide good estimates of NDF for first cutting alfalfa in normal years. However, we don’t know if these relationships hold this year because of multiple killing frosts after substantial growth in many locations.

Scissors-cut samples were taken the first and second and third week of May from 16 alfalfa fields across the state. New fields located in Falmouth, McBain, and Marion, Mich. were added to the samples. Samples were analyzed by wet chemistry for NDF and correlations with PEAQ stick measurements and GDD were evaluated.

Results of the May 14-15, 2012 sampling:

 City

 5/1-2
 LAB NDF

 5/7-8
 LAB NDF

 5/14-15
 LAB NDF

 5/14-15
 PEAQ

 5/14-15
 GDD

 5/14-15
 GDD NDF

 West Olive

 28.7

 35.5

 36.2

 38.4

 752

 40

 Zeeland

 29.7

 37.4

 37.8

 39.2

 752

 40

 Zeeland

 30.5

 37.2

 37.6

 36.4

 752

 40

 St Johns

 28.3

 33

 34.4

 32.6

 698

 38.5

 St Johns

 30.5

 35.5

 41.2

 36.1

 698

 38.5

 St Johns

 29.4

 36.2

 38.5

 36.1

 698

 38.5

 Portland

 31.1

 35.4

 35.8

 35.9

 693

 38.3

 Coldwater

 31.0

 36.4

 35.9

 38

 873

 42.9

 Quincy

 29

 36.5

 36.7

 39

 873

 42.9

 Jonesville

 30.6

 35.1

 37.8

 *

 840

 42.2

 Brown City

 26.4

 30.2

 32.3

 32.9

 644

 36.8

 Brown City

 28.1

 32.8

 35

 35.2

 722

 39.1

 Marlette

 26.4

 30

 30.5

 32.5

 640

 36.7

Falmouth



 27.6

 **

 527

 32.7

 McBain



 26.9

 **

 527

 32.7

 Marion



 30.6

 28.7

 527

 32.7

* field was harvested before PEAQ measurement was taken
** alfalfa was not tall enough to measure using PEAQ stick

For fields that have been previously sampled, LAB NDF only increased 1.4 percentage units from 34.7 percent to 36.1 percent over the last 7 days; an average increase of 0.2 percentage units per day. However, the increase ranged from -0.5 to 5.7 percentage units across locations. NDF predicted by PEAQ increased 3.7 units over the last week while NDF predicted by GDD increased 3.3 units, both were greater than the 1.4 units increase measured by the LAB.

For all locations (including the 3 new locations), NDF predicted by GDD was 3.6 percentage units higher (38.2 percent) than the LAB values (34.6 percent) with a range of -2.7 to +6.2 units. NDF values predicted by PEAQ was 0.1 percentage units lower than the LAB values with a range of -5.1 to 2.3 units. However, PEAQ was not measured on several samples (see table footnote).

Overall, the increase in predicted NDF values by GDD and PEAQ was not reflected in the lab values. NDF values predicted by PEAQ are now closer to the lab measured values than GDD predicted NDF values.

This year, because of setbacks in growth by the multiple frosts, we are predicting that alfalfa should be at 40 percent NDF around 850-900 GDD. Typical recommendations are to begin cutting alfalfa at 750 GDD for upright silos and 680 GDD for horizontal silos. According to data collected in the upper Midwest over several years, alfalfa typically averages 38 percent NDF at 680 GDD and 40percent NDF at 750 GDD. Filling horizontal silos with layers of alfalfa of increasing maturity will allow harvest to begin a little earlier because the layers of alfalfa are blended as the alfalfa is removed from the silo. Visit the MSU Enviro-weather website for the Alfalfa Cutting Model predictions for GDD corresponding to your area.

Alfalfa harvest began last week (week of May 14) for most locations in Southern Michigan. Central Michigan and the Thumb area began harvesting the week of May 21. Weather forecasts are predicting GDD to reach 850-900 in the East central part of the state on Friday May 25, 2012 and in the McBain sampling area around the first week of June. Sampling will continue for the week of May 21 and results again will be reported through MSU Extension News

Financial support for this project has been provided by Byron SeedsCumberland Valley Analysis Services, Inc.Mycogen Seeds, and Pioneer Hi-Bred Int’l.

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