NIRS Training Workshop
Paolo Berzaghi joined us to present sessions at our summer NIRS training workshop held July 30th and 31st, 2002 at the Pyle Center on the University of Wisconsin, Madison campus.
Training topics included spectra and file handling, using NIRS for lab quality control, and local calibration development. We also learned about using NIRS to determine if wet chemistry values are good. The training was a great success and thanks to all who participated!
If you would
like any information from the training sessions, please contact Patty Laskowski
Results of Summer 2002 Board Elections
Thanks to everyone who participated in this year’s board elections, including those serving on the nominating committee: Dave Taysom, Mick Goedeken, and Don Sapienza.
Those Elected are as follows:
Brian Shreve, Commercial Lab sector
Mike Siedell, Gov. & University sector
Sam Stratton, Plant Breeder sector
The Board of Directors to take office, or continue serving their terms, for the 2002-2003 fiscal year beginning on October 1 will be as follows:
Steve Peterson, AgSource Coop
Christine Henderson, Stearns DHIA
Brian Shreve, Servi-Tech Labs
Don Sapienza, Pioneer HiBred
David Johnson, CAL-WEST Seeds
Sam Stratton, FFR Coop
Neal Martin, US Dairy Forage Research Center
Dan Undersander, UW Agronomy
Mike Siedell, Univ. of Nebraska at Lincoln
Summary of the Released Equations
- Susan Selman
The Corn Silage Digestible NDF (dNDF) and NDF Digestibility (NDFD) Package hit the shelf June 2002 for participating labs. The samples were supplied by commercial testing labs for analyses to be completed at Marshfield. The samples were either oven dried or micro waved before 48 hr in vitro testing and subsequent equation development. We are recommending oven drying for this assay before scanning. When looking at samples that have been split, either oven or micro waved; the fiber content of the micro waved samples tends to be higher. We believe the fiber content is changing by using the microwave. Now that corn silage season is going to be approaching us soon, we need to remember to save spectra that are spectrally different to help update the equation for the next season.
As an added bonus the Legume-Grass Hay and Haylage dNDF and NDFD Package hit the shelf at the end of June 2002. Again, our consortium members supplied most of the samples. The analyses were completed at Marshfield, with most of the samples being oven dried before 48 hr in vitro testing. We have added a handful of micro waved samples to this equation to broaden our database. We are also recommending oven drying for this assay before scanning. The fiber content tends to be higher on samples that have been micro waved. Updating this equation is essential, with such a small database, saving samples with spectra different from the equation is beneficial.
Don’t worry plant breeders, your equation for dNDF is just as important. The samples for this equation were collected by the breeders. We tried to add a Canada sample set to help increase the database; but it was clearly a different population from the breeders’ set. So the Canada samples were not added to your equation. Updating your equation is very essential because of the very small database. Please remember to submit both your spectra and samples from the various harvests (and locations if possible).
For calculating the dNDF and NDFD from each other please remember to use the NDF2 supplied with these equations, otherwise NDF from original equations should be reported. Reasoning for this is that the original equation and the dNDF equation are from different populations. The original equation has had samples added from over the years. The dNDF equations are from small databases, but with continued updating this will help make the NDF2 a more robust equation.
What’s Going on with IVTDMD?
- Susan Selman
IVTDMD is a wet
chemistry measure of the digestibility of the feed stuff.
In the release
of the hay and haylage dNDF and NDFD package, as well as in the corn silage
dNDF and NDFD package, the term IVTDMD will be found.
In Vitro True Dry Matter Digestibility is the
incubation for 48 hours of feed stuff in rumen fluid and buffer. The undigested residue is extracted in
neutral detergent solution. In Vitro’s
are based on direct measurement of fiber degradation. Alone, the number has value in determining which feed is more
digestible. Example: two hays were
analyzed as having IVTDMD of 75% and 82% digestibility. It’s clear which has the higher digestibility
(82%). This assay has been taken a step
farther, though, being used in determining NDFD (NDF Digestibility, % of
NDF). NDFD is the % of total cell wall
that is digestible. Example: two hays
were analyzed having IVTDMD of 82% for each but the NDFD were 53% and 46%. In this example the hay with the 53% would
be more digestible. NDFD is an
additional tool to help accurately assess forage quality.
Best part of all of this is that it ties in with the
new RFQ.
Status of Relative Forage Quality (RFQ)
- Dan Undersander
John Moore (retired beef cattle nutritionist, University of Florida) and Dan Undersander (forage agronomist, University of Wisconsin) have reported on RFQ at the National Forage Testing Association Symposium, Dubuque, IA, the American Forage and Grassland Council National Meeting, Bloomington, MN, and the Florida Nutrition Conference, Gainsville, FL. In all cases the new index was well received.
The key differences between RFV and RFQ are the use of NDF digestibility in the TDN and intake functions for legumes and legume/grasses mixtures and a separate equation for grasses (both warm and cool season). The equations are based on in vivo animal data where possible.
RFV and RFQ are designed to have the same mean and range so that rules of thumb and pricing from RFV should apply to RFQ. However, individual values will differ significantly between the two indices as shown in the graph below where individual samples may differ by 50 pts.
An initial data analysis indicates that RFV and RFQ were linearly related for scissors clip (hand clipped alfalfa from first cutting in Midwestern states). This means that we can use the forage quality sticks and previous scissors clip.
This raises the question: where will RFV and RFQ likely be different? We are initiating several studies to get a better understanding of factors affecting digestible fiber and you will likely hear much more about this in the future. Following is a summary of the little we know:
· Fiber is more digestible when grown under cooler conditions. Therefore
o First cutting will tend to have more highly digestible fiber than later cuttings growing under higher temperatures.
o The same crop grown in northern states or Canada will tend to have more digestible fiber than when grown in states to the south.
o Alfalfa grown in higher mountain valleys of the West will have more digestible fiber than that grown in lower valleys.
·
Fiber
of leaves is both lower in content and higher in digestibility. Therefore harvesting losses will result in
greater RFQ loss than RFV
· RFQ is reduced by heat damage but RFV is not.
In summary, I expect bigger differences between RFV and RFQ on harvested forage than fresh cut, and bigger differences between different cuttings.
For
your information, a copy of the article, Relative Forage Quality: Indexing Legumes and
Grasses for Forage Quality from
June, 2002 is included here.
Using NIRS Equations Based on Biological Assays
|
SED: |
2.376 |
Num. |
Samps: |
52 |
|
|
|
Means: |
20.644 |
21.761 |
Std. |
Devs: |
6.776 |
5.741 |
|
Bias: |
-1.117* |
Bias |
Limit: |
0.6 |
|
|
|
SED(C): |
2.117* |
SED(C) |
Limit: |
1.3 |
|
|
|
Slope: |
1.128 |
RSQ: |
0.914 |
|
|
|
Because we have seen that components such as RUP, soluble protein, and digestible fiber appear to be different between microwaved and oven dried samples in the resulting NIRS scans, we are recommending oven drying only for those NIRS equations that are based on biological assays. Microwaving may be changing some of these components in a way that alters the report of how they would actually respond in the animal.
Digestible Fiber Analysis of Alfalfa and Grass/Lgume Mxtures
-Dan Undersander
The NIRS Consortium released IVTDMD and dNDF, with a calculation for NDFD for alfalfa and grass legume mixtures equations this June. The equations seem to be working very well. Farmers and nutritionists who have used digestible fiber in their ration balancing have been extremely satisfied.
When we first released the equations last spring, we monitored performance very carefully. There were reports that values were low. In response to these concerns we sent two ground check samples to several laboratories and compared results. The results were as shown in table below:
|
|
Bias |
|
|
Lab number |
NDF |
NDFD |
|
1 |
1.8 |
5.0 |
|
2 |
-2.4 |
-4.0 |
|
3 |
-0.9 |
-2.4 |
Note that biases for both parameters followed the same trend for both labs. We felt that we needed to add to the equation but also that part of the problem was differences in sample handling and preparation. We used the samples that labs had submitted earlier, selected 52 samples, and had UW Marshfield run in vitro on these samples. These samples were added back to the equation and performance has improved greatly (performance is shown in table below). New equations have been released to all participating labs.
For dNDF of added samples
The revised equations seem to be performing very well and we will continue to monitor them with your help.
A few important considerations to help improve output of results:
1) We should try to use common terminology. The recommendation is to follow NRC and use dNDF for digestible NDF expressed as a percent of dry matter and NDFD for digestible NDF expressed as a percent of NDF.
2) We recommend reporting the following parameters: IVTDMD and NDFD. We do not recommend reporting the NDF2 from these equations or dNDF. We feel that these additional parameters will simply confuse the public.
3) The equation estimates its own NDF2. This term, not NDF from other equations, must be used to convert dNDF to NDFD. This NDF2 estimate will be close to other estimates but not the same. It is based on spectra from 5000 instruments not trimmed to 4500 as other equations. We are in the process of converting all equations to 5000 instruments to improve accuracy.
4) Be prepared that TDN values calculated from this estimate are lower than historic TDN values and some may consider them erroneous but the 2001 NRC for Dairy Animals has lowered TDN values for many feedstuffs.
5) The new test is very sensitive to heat damaged hay or haylage and will give significantly lower values where heat damage is present. Nutritionists have never adjusted energy down for heat damage but the little research that has been done suggests it should be.
Spectra Collection for Equation Updates
Labs should collect any spectra that does not fit current equations. Collect spectra for 3 to 4 weeks or until a good file is formed. After this, send the spectra to Susan, after which she will review the spectra and determine which spectra require the sample to be sent to Susan (and chemistry if available). It is expected that this process from time of the lab sending in spectra to Susan slselman@facstaff.wisc.edu (ph:608-264-5232) selecting the samples and replying to the lab should not take more than 10 days. Especially with the drought in the Dakotas, Nebraska, and Kansas, these samples might be good to keep for equation updates. Some labs have already submitted spectra. Keep up the good work!
Forage Check Cells- Reminder
Most labs have sent an old soybean check cell in to Susan for repacking and have received their new Consortium Forage Check Cell. If you haven’t had your equation checked, please follow the directions Susan sent with your new forage check cell equation. Then send in your chk and eqa files to Susan. Most equations need adjustments to fit each lab’s NIRS instrument.
For further information on any of these topics, please contact Patty Laskowski.
Patty
Laskowski
NIRS
Consortium
5205
Schluter Rd.
Monona,
WI 53716
ph:
608-661-7678
fax:
608-442-5378
Email:
pmlaskowski@facstaff.wisc.edu
