Both nutritionists and dairy producers spend a lot of time reviewing forage analysis reports. Knowing what we are feeding and making needed adjustments for a consistent nutrient supply is crucial for success. This important task may be part of a buying decision, a final report card on a silage harvest, or part of the ration formulation step.
My guess is that each of us have some key nutrients on the report where our eyes go first. Then, there are a few other nutrients that will answer the question of how this forage will fit into the ration. I bet that this nutrient list of interest varies between people. There are probably also valuable numbers on the report that are routinely ignored due to lack of experience.
Though we likely have a different order of importance, there might be what we can call the big five values. These would be neutral detergent fiber (NDF), crude protein (CP), NDF digestibility (NDFd), ash, and dry matter percent (DM). Your list may be different. Maybe your list is not really a list at all but one number like relative feed quality (RFQ) or milk per ton (MPT). In any case, I think there is a less-noticed indicator that has become more of a predictor for me of how much I am going to like how a forage handles and feeds. This is a value that nutritionists will be familiar with, but most producers probably skip right over it. What is this sneaky-good metric with so much to say about a forage? It is abbreviated ADICP and might also show as ADF protein on a forage report. These terms are not synonymous, but they are getting at the same thing.
Acid detergent insoluble crude protein is the full name for this measurement. In the lab, it is protein that is not solubilized in an acid detergent bath. It is similar to the way ADF is determined. In either case, if a protein or a fiber is not broken down by an acid bath and subsequent rinse, it is probably also unavailable in the cow. Most producers are familiar with ADF but not so much with ADICP.
Where does it come from?
The protein in ADICP isn’t 100% unavailable to the cow, but it is close. It is classified as the slowest and most poorly digested protein in the pool system set forth in the nutrition modeling process. In a high-producing dairy cow with high intake and a high rate of passage, this protein is not much help. Let’s look at why protein ends up as ADICP and why I think it is such a good indicator that you probably won’t like a silage with high levels.
The primary cause of elevated ADICP in a forage is due to heating after harvest. An important part of this process is known as the Maillard reaction. This is a browning process where sugars in the plant react with protein, rendering both mostly unavailable to the cow. The sugar and protein in the ADICP is lost for feed value. Most dairy folks will know what “tobacco alfalfa” looks and smells like. It is actually a nice smell, and the cows seem to not mind at all; in fact, I think they like it. A big part of this heating process is the Maillard reaction, and the result will be higher levels of ADICP. Even though the cows like it, the feeding value is reduced.
In silages, this process is a bit trickier. The overwhelming smell of silage acids may mask the slight burned smell that is so evident in the brown alfalfa hay. But the nutritive result is the same. If the fermentation process is not ideal and excessive heat is the result, it is likely that ADICP will rise and the value of the silage will fall. If the values are correctly entered into a good nutrition model, the nutrient shortages can be addressed in the rest of a balanced ration. The nefarious part of higher levels of ADICP are the many other problems that seem to be in play with silages with high ADICP.
If you think of all of the potential risks to making good silage, nearly every one will raise ADICP. These include silage that is too wet or too dry, incomplete packing or covering, being too slow to pack and cover silage, and the presence of contaminates like ash and dirt. All of these risks are easily evaluated by a close inspection of a silage product with your eyes and your nose. In most cases, if your nose and eyes don’t like the silage, ADICP will be higher than desired. So, if you are unable to inspect silage in person, I think you can consider using ADICP as an overall “good feed” or “bad feed” indicator.
Know what to look for
First off, let’s discuss the unit for this metric. The best way to express it is as a percent of CP. Thus, when comparing a high protein forage like alfalfa haylage to a lower one like corn silage, you consider the number in view of the amount of protein in the forage. What are good levels for various forages? I see levels less than 5% for some really nice silages. With less awesome forages like a haylage that grew too long, was too dry at harvest, and had more ash than desired, this value could reach between 10% and 15%. Heat-damaged dry hay can also have over 10% of the protein as ADICP.
After all the details of how sugars and protein can become intertwined and undigestible during the ensiling or curing process, you can boil this down to one thing: if you see a silage with less than 5% ADICP, I bet you are going to like it. If the ADICP is over 10%, my guess is it won’t smell great, it might be too wet or too dry, and it may have visible mold and excessive spoilage. I often do rations using analysis reports of forages I have not actually seen, handled, or smelled. If the ADICP is higher than it should be, I will advise the dairy to be careful, send additional samples to the lab, and maybe ask for a fermentation analysis.
To sum things up, good silage has low ADICP. My guess is that this is an underutilized measurement that is usually overlooked as a producer studies a lab report. Maybe it doesn’t make it into your top five list of metrics to look at, but I bet you will find it to be reflective of the positive or negative realities of the values we all look at first. Maybe you should make it number six on your list.
