I had the opportunity recently to sit in a room with leading dairy nutritionists from across the U.S. Among other things, our discussion covered the ration forage percentage common in each of our regions. It was very interesting to learn about the factors influencing ration characteristics in each area. It will be no surprise to report that the further west you go, the less forage is fed. This is the case for both lactating and nonlactating diets. The overwhelming reason for the geographic trend is annual rainfall and ease of forage production.
Consider that in adjacent fields an Upper Midwest or Eastern dairy may put in drain tiles to make tillage possible. In the same fields in the High Plains, there might be a drilling rig popping a 300-plus foot hole in the ground to reach the Ogallala Aquifer. Further west, there may be an irrigation ditch running full yet passing by a fallow field on a dairy as it heads toward someone with more senior water rights. It makes sense, then, that forage inclusion in the resulting typical diet can range from over 60% to around 30%. That is a big difference considering the dairy cows being fed in New York, Minnesota, Kansas, or California have pretty much the same nutrient requirements.
How can we build successful rations in these disparate situations? The answer is found in the fact that cows have nutrient requirements, not ingredient requirements.
Depends on how you use it
Keeping this in mind, why is “forage quality” one of the most common terms analogous to successful dairy production? First, let’s better define what most would understand when hearing the term “good quality forage.” For hay and silage, characteristics including high protein, low fiber, and high digestibility would top the list. From these lab-derived nutrients, we would make further calculations to describe good forage as having high milk per ton or relative feed quality (RFQ). These metrics might even be used to pick which forage wins the hay contest at the county fair or even in Madison!
Since we live and work in an economic dynamic of buying feed to sell milk, shouldn’t the best quality forage be the one that has the best economic return for the producer? “Ah, yes,” one might say after a minute of thought. “Of course, you probably shouldn’t buy the top hay since it is probably overpriced. Drop down a little on RFQ, and you will get a better buy.” Yes, this is true, but this isn’t really what I mean. My point here is that a dairy cow has a requirement for nutrients including protein, fiber, starch and other sources of energy, and various details like vitamins and minerals. The best quality forage for a particular ration is the one that fits the best when considering the cost and nutrient content of the other ingredients that will be fed alongside.
I say often that the calculations we do to build diets is math you can’t do in your head. If you plan to not use a nutrition model to carefully formulate a diet but instead feed your cows a ration of 100% forage, then yes, the “highest quality” forage you can find will probably make the most milk. But if you plan to combine multiple ingredients together that complement each other, the simple quality assessment will fall short if maximum margins are your goal.
Two examples
This decision between seemingly higher or lower quality forage options has two very different realities depending on if you are growing or buying the forage. When purchasing forage, utilizing a good analysis from the lab along with information and prices of the other ingredients available will allow for the best decision to be made. If you are growing the forage, the decision depends on the plan your economic analysis would suggest, and then variables like rain, wind, and heat units will play the final role. Let’s look at an example of each that allows economics and nutrient values to help you decide what truly is the best quality forage for a particular diet.
First, let’s consider a dairy that purchases alfalfa hay to supply around 10 pounds of dry matter in a lactating diet. The first choice is an early cut hay that, in every respect, would qualify as a number one hay. Assume the protein is high at 24%, neutral detergent fiber (NDF) is low at 31%, and that this fiber has excellent digestibility at 30 hours (NDFd30) of 50%. Due to the high protein and digestible NDF, the NDF undigested at 240 hours (uNDF240) is very low at 12%. This sounds like a really good hay choice that should support high milk production when included in a balanced diet. Assume the cost is $275 per ton out West.
The second choice is also a nice alfalfa hay, but due to a few more days of growth, the protein dropped to 19% and NDF rose to 40%. This more mature hay lost some digestibility, so NDFd30 is lower at 44% and uNDF240 is higher at 17%. Assume this hay is a bit cheaper at $225 per ton. In every respect, this hay, by itself, would support less milk. But since we don’t plan to feed it by itself, let’s use the model to help us decide which hay is the best purchase.
In reality, we would need to know the price of every ingredient to be fed along with the hay we choose. For this exercise, let’s just consider two ingredients that would have variable inclusion rates depending on which hay we buy: soybean hulls and canola meal. If we choose what we would consider the better-testing hay (choice A), we would feed for example, 4 pounds of canola and 2 pounds of soybean hulls with a higher inclusion of the hay. If we choose the more moderate-testing hay (choice B), the canola might jump to 5 pounds and the soybean hulls up to 4 pounds. So, if the hay cost is $275 and $225, which should we buy? Well, it depends on the price of the canola and the soybean hulls. It is likely that other ingredients in the ration would move up or down as well, but the nutrients supplied by the canola and soyhulls offer the opportunity to, in a sense, “fix” the lower quality hay. If canola and soybean hulls are cheap, the lower cost hay is likely the choice. If these purchased grain ingredients are high, it is likely a better choice to pick the more expensive and better testing hay. As mentioned before, this is math you can’t do in your head.
The situation of growing your own forage is much the same with an added dimension that may not always track in purchased forages. Assume we are considering a small grain silage crop like wheat or triticale. If we harvest in the flag stage, we may have crude protein in the high teen levels, high sugars, and surprisingly low and highly digestible NDF. The problem here is that the yield will be lower and thus cost per ton will be higher. It will also likely be more difficult to harvest and ensure a good fermentation process.
But if canola or other protein sources like soybean meal are expensive and digestible fiber sources like soybean hulls are either difficult to get or are also expensive, this lower yielding, more expensive silage is probably the best cost option for the final ration. However, if the purchased protein and by-product ingredients are abundant and cheap, the better choice will likely be to let the crop grow a few more weeks and harvest a much higher yielding forage that will be cheaper in the ration. When feeding this material, the inclusion per cow may be a little lower and the grain ingredients will add the lost protein and digestible fiber needed for the cow.
The “right” choice is not always the same
In the real world, it is rarely this cut and dry. However, these principles should always be present in the mind of a dairy producer growing or buying forage. No matter if the forage fed is considered high quality or more of a high fiber, low protein option, the ration put in the bunk should be the same. When we have “low quality” forage to feed, we should not expect less milk production. If there is enough availability of various protein ingredients and digestible fiber-rich by-products like soybean hulls and beet pulp, the correct diet can still be put in front of the cow. Though much of the effort in this process happens in the lab and on a computer, the physical form, forage length, and other factors of these forages must be considered when the ration is mixed on the farm. Adding or removing knives and varying mixing time for different rations is a must to be sure that every diet is placed in the bunk in the correct form. A Penn State Particle Separator can be used to ensure this step is completed correctly.
One last note: Forage quality does include things like being free of anti-nutrients such as mold, mycotoxins, dirt, and excessive weeds. We know what good feed is when we see it. We just need the lab to complete the final details and then let the computer help us make the best decisions for the final ration fed to the cows. The right forage choice will be the one that offers the highest margin while supporting good cow health.
