Managing haylage variation in rations (Part 2) – Jon Rasmussen, Vita Plus
In part one of this series, I discussed how we can better manage haylage in the field to minimize quality variation. Now, we will turn our attention to how dairy nutritionists manage haylage variation in the ration.
Twenty years ago, it wouldn’t have been out of line to state that dairy nutritionists mainly focused on the crude protein (CP) and neutral detergent fiber (NDF) levels to determine how much haylage and what other supplements were needed to balance the diet. In those days, we aimed for a specific NDF level in the diet and the cows would either agree or disagree if that was the correct amount. We would then make the necessary corrections to bring back milk production and health. These were slow and challenging learning experiences.
The frustrations with this dietary guesswork led to the development of NDF digestibility. With NDF digestibility, benchmarks indicated NDF could have higher or lower rates of digestion. This gave nutritionists some guidelines to help make diet adjustments. However, dietary guesswork remained as it was difficult to apply forage digestibility measures to diets with supplements that did not have the same digestibility measures.
The wonderful thing about these discoveries is that they forced us to keep learning and improving. In more recent years, another big improvement came with the discovery that we could utilize some of the fractions that made up NDF digestibility for forages and supplements. The main fraction that has helped advance diet formulation has been the undigestable NDF (uNDF). As haylage tends to vary more than corn silage in the amounts of NDF and uNDF, this knowledge has significantly reduced the guesswork in diet formulation.
To explain why this is important, let’s use an example diet with two different haylages being fed at the same level. Our example diet feeds 55 pounds of dry matter intake (DMI) and 15 pounds of haylage on a dry matter (DM) basis. The first haylage is first crop with 35 percent NDF and 15 percent uNDF. Some basic math will tell us we are getting 5.25 pounds of NDF and 2.25 pounds of uNDF from just the haylage. If we switch to feeding third crop with 30 percent NDF and 15 percent uNDF, we will now have 4.5 pounds of NDF and 2.25 pounds of uNDF.
Historically, we would have increased the amount of haylage in the diet by replacing first crop with third crop as an attempt to match NDF levels. Today, we know that isn’t a good idea as it will increase rumen fill and provide less energy to the cows. This helps take the guesswork out of diet formulation and keeps cow performance and health on the right track.
Developments, such as ash-free NDF (aNDFom), uNDF, and NDF digestion rates, have also helped us fine-tune diets and teach us not to get frustrated when including more haylage in our diets. This really helps in areas where hay is desired to be a significant part of the cropping rotation.
Feed quality and nutrition