Make a Good Cow Soup

One of the papers presented at the American Dairy Science Association meeting in June discussed the variability in forage test results from different labs. Researchers at Utah State University sent three forage samples to twelve laboratories in duplicate for three months. Results were not encouraging. Relative feed value (RFV) for the same alfalfa hay ranged from 101 to 176. NDF ranged from 35 to 54% with a standard deviation of 3.5 units for the same hay. Even crude protein varied from 21 to 29%.

So, it made me think about the prediction accuracy of our dairy nutrition models considering the intrinsic inaccuracy of the inputs, i.e., the nutrients.  I’m not a modeling guy but I admire the progress dairy scientists have made in predicting cow performance with a mathematical model. Sometimes they work great. But assembling a giant digestive jigsaw puzzle with some of the wrong puzzle pieces only looks like part of the picture. Like the old saying,” garbage in, garbage out”.

So, what do we do?

The good news according to Jerry Severe, one of the authors of the paper, is that some of the labs had much less variability than others. The National Forage Testing Association ( evaluates and certifies labs. I’ve found that the dairy forage labs I work with are very cooperative if there is a question about a result. They are always striving to put out the most accurate results in the least amount of time. But I don’t hesitate to cross check with other labs or with duplicate samples.

Make sure you get a representative sample of the feed. I don’t want the lab to have to subsample the feed I send in. It creates one more opportunity for error. Use the bag that the lab provides – not a full sleeve with the fingers full of feed too.

I titled this column, “Cow Soup”, because like soup, the right combination of ingredients makes great tasting soup. The same is true for the rumen. Optimum fermentation for healthy cows with high production is achieved when the individual ingredients complement one another. This is the associative effect of the individual ingredients in the rumen. Each ingredient affects the digestion of another, just like each ingredient enhances the others in good soup without overpowering the flavor.

Practiced nutritionists have knowledge and experience of how each ingredient digests and how they might affect the rumen fermentation. It’s not just about balancing for nutrients. The balance of the ingredients that provide these nutrients is also a factor for microbial protein production, metabolizable energy, dry matter intake and milk production. You can deal with some variability in lab results if you know from experience what blend of ingredients makes a good ration.

I occasionally use Fermentrics to check the associative effects of ingredients. Fermentrics is a diagnostic test that measures the rate of gas production from fermentation of the TMR or individual forages in rumen fluid. I’ve found that the digestion kinetics and microbial biomass provided by Fermentrics are better than a simple nutrient analysis for predicting production. 

In the end, the cows are the ultimate lab. I think it will be a long time before a computer model will replace a little manure on the boots.


Reference: Severe, J. and A.J. Young. (2017). J. Dairy Sci. Volume 100 (suppl. 2) page 264.