Monitoring Dry Matter Intake

Dry matter intake (DMI) is the biggest driver of milk production so it only makes sense that it should be monitored as closely as milk production.  Dry matter intake is a measure of what is presented to the cows minus what is remaining when the next feeding is provided.  It can be impacted by a number of factors, but unless you have a good idea as what the true DMI on your farm is it will be very hard to trouble shoot when a problem does arise.

In order to track DMI the dry matter of the ration and the refusals need to be monitored regularly.  If the herd is fed using a component feeding system then the dry matter of the individual ingredients also need to be tracked.  Like any type of analysis, getting a good representative sample is the first and most important step to the process.  Sampling a total mixed ration can be difficult, but taking a sample right at the mixer is one of the best ways to get a good sample.  A refusal sample should be taken from the refusal collection from the entire herd, not just what was in front of a couple of animals.  Once the sample is taken it is dried in either a Koster tester or a microwave oven until the weight of the sample no longer changes.  The dried weight is then divided by the wet weight to determine the dry matter percent.  Although there will be fluctuations in dry matter from week to week, if there are big changes then mixing of the total mixed ration should be investigated to make sure it is being done properly.  

The other aspect of monitoring DMI requires that the amount of feed being presented to the cows is known.  Mixing and delivering the ration as close to what is on the feed sheet should always be the goal.  Scales that are not calibrated correctly or not working well can significantly change what is being presented to the cow.  Therefore, checking the scales every week is a good practice to get into and does not take a lot of time.  A less precise way to monitor mixing of the ration is to track feed inventory on the farm.  If grain bins are getting empty faster or slower than would be expected based on the formulated ration this indicates a problem.  Either there is a problem with mixing the proper amount of each ingredient, or pests (birds/rodents) are eating the feed from the storage area.  Pests can also eat the feed once it is in front of the cow, which can make DMI look greater than it actually is.  Pests will not only impact feed inventories and DMI, but they can also spread disease so trying to eliminate them should be a priority.

Lastly, in order to get the full picture of DMI on the farm, the refusals from each group of animals needs to be weighed.  Depending on the feeding situation on the farm this job will be easier for some than others.  However, it is worth the effort because simply eye-balling it is not always the best method of estimating how much the cows are not eating because gradual changes in intake may go undetected until they reach a significant threshold.  If problems in intake are detected early it may be possible to correct them before they lead to big changes in milk production.  Therefore, taking the time and effort to weigh back refusals a least a few times a month will keep the eyeballing method honest and may head off some bigger problems.