What is in Manure?

Manure can be both a blessing and a curse on many farms.  It is a great fertilizer for the crops, but it also has to be managed diligently from when it comes out of the cow to when it is spread on the field to ensure that it is all ending up where it should.  From collections systems to storage and spreading there are many things to consider about manure management, but one benefit to manure is often overlooked.  It is a great indicator of the health of your cows and how well they are utilizing the diet that is being fed to them.

There is a great deal of effort put into creating a well balanced ration and presenting it to the cow, but after that the cow and her rumen microbes are in control and do we really know what is happening in there?  Yes, we know a great deal about how feeds are digested and utilized, but every farm and every cow are different.  Therefore, the only way to determine how cows on your farm are utilizing your diet is to look at the manure.  Many producers look for loose manure as an indicator that there might be too much protein in the ration or too many concentrates in general.  Some even look at whether there are corn kernels in the manure.  Identifiable corn in the manure is a good sign that not all the corn in the ration is being utilized for milk production.  

However, not many look beyond the looseness of the manure or whether there is corn in it.  There is more that can be learned from the manure and it requires that a manure sample be taken and sent to a lab for analysis.  Manure analysis do not need to be done as often as forage analysis, but looking at it once or twice a year might yield some surprising information.  From an environmental perspective looking at the phosphorus content of the manure will give you a good idea as to whether the diet is providing the right amount of phosphorus to the cow.  Manure phosphorus levels should be between 0.55% and 0.7% in a diet that is meeting the phosphorus requirements of the cow without providing too much.  Manure can also be analyzed for neutral detergent fiber to determine how well the fiber portion of the ration is being utilized.  Starch is also a great thing to measure because it will quantify how much of the starch from the corn in the manure is being excreted.  

In order for manure analysis results to be useful they first need to be taken properly.  The general rule is that 15% of a specific group or up to 20 cows should be sampled.  The sample should be of fresh manure, which means palpating cows or obtaining samples from piles that have recently hit the floor and are not contaminated with feed or bedding.  As with any sampling, it is important that the sample is representative of the entire group.  Samples from all the cows in a group are mixed together and sub-sampled.   The sub-sample is placed in a well sealed container and shipped overnight to a lab that performs manure analysis, or should be frozen if not mailed immediately.  This analysis can take two to three weeks to perform.  The results need to be interpreted relative to the ration that specific group was eating at the time of the sampling.

Having done many manure analysis I understand that it is not something that folks are eager to do, but it is another tool that can be utilized on the farm to help ensure that the ration is being utilized as efficiently as possible.