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Nieves Núñez Romero
Posted on Thursday, May 12, 2005 - 4:31 am:   

¿Does anybody have any information whether it is possible to determinate the minerals in animal feed with nir?

Regards,

Nieves, Spain
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Dennis Karl (Dennisk)
Posted on Thursday, May 12, 2005 - 3:08 pm:   

Hi Nieves, Your message seems to have resent itself. I think the others who responded indicated it is not generally possible to do what you want to do. Our experience in our animal feeds laboratory is that you will be wasting your time. We struggle to simply measure the total ash content with any degree of accuracy and precision. Certainly we would not be able to measure individual minerals in compounded stock feeds.
We have been able to use NIR very successfully to measure minerals such as Na, K, Ca, Mg and P in fresh forages. However when inorganic minerals are added to forages for any reason, eg Mg salts to treat cattle for grass staggers,this addition was completely 'invisible' to the NIR.

Hope this helps
Regards
Dennis
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k. Lee
Posted on Thursday, May 12, 2005 - 4:23 pm:   

Would x-ray fluorescence work for minerals in feed? It will work with little sample prep and is non-destructive, and I think it is relatively easy to perform. I don't know about the sensitivity.
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hlmark
Posted on Thursday, May 12, 2005 - 6:24 pm:   

If I remember correctly, XRF can detect minerals, but the sensitivity will very much depend on the type of instrument as well as the details of its design.

Energy-dispersive XRF, as I recall, is generally good down to about 0.1%, but tends to be insensitive to atoms of low atomic number, e.g., sodium and lighter atoms.

Wavelength-dispersive XRF is more sensitive and deals better with low atomic weight compounds, but quickly gets very expensive.

I used to know more, but it's been a long time.

Howard

\o/
/_\
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Dennis Karl (Dennisk)
Posted on Thursday, May 12, 2005 - 7:26 pm:   

Howard is quite correct. We have also investigated using XRF and it is insensitive to sodium and potassium. Contrary to a comment by K Lee,sample preparation does actually require a lot of effort and attention to detail. Because of the small 'foot print' of the area being measured the 'sampling' by the energy beam is critical. Feeds require grinding down to very fine particle size to reduce this 'sampling error' problem.
Our experience has shown that you cannot go past AAS (or ICP if your sample numbers can justify it)for accurate determination of minerals in feeds.

Dennis

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