Expanding the Digestible Fiber Pool
Probably the greatest advancement in dairy nutrition over the last 30 years has been our increased understanding of digestible fiber. NDF [neutral detergent fiber] was considered monolithic and there were no differences when we plugged in the NDF of corn silage, alfalfa, warm and cool season grasses. Now, with metrics such as NDFD30 and uNDF240 we know there are tremendous differences. Properly testing and attributing value to digestible fiber has allowed milk production to dramatically increase and for better utilization of forages in dairy diets. The next frontier will be an increased focus on feed efficiency and will also be centered on expanding the digestible fiber pool.
NDF has long been considered a negative because too much NDF can limit intakes and therefore milk production. But with a new look at fiber we are seeing that effect as a potential tool for increased feed efficiency. To discover how much digestible fiber our forages have, we need to look at the two parts of the equation – the NDF and the digestibility % of that NDF, or NDFD30. So, if a sample is 36% NDF with a 50% NDFD30 we'll have 18% digestible fiber [dNDF30] in 30 hrs.
This dNDF30, along with uNDF240, is key to increasing the forage percentage in the diet and increasing feed efficiency. By expanding the digestible fiber pool, we are able to decrease concentrate and increase rumen retention times to allow for even further digestion and more energy. This combination allows the cow to get more value out of every pound of feed. More milk with less manure is a powerful combination if it can be accomplished without losing body weight.
How do we get there? Historically, many farmers have used corn silage and alfalfa as the pillars of their forage program. While corn silage has better digestibility then alfalfa, neither had a very large fiber pool [NDF] and so while low-lignin alfalfa and BMR corn are improvements in the digestibility of the fiber, they only affect one side of the dNDF equation. For instance, a 4% increase in the NDFD30 of a 35% NDF alfalfa sample will only increase the digestible fiber levels by 1.4%.
To truly increase the digestible fiber pool in our forage systems, we need to be looking at forages that have higher amounts of fiber that are very digestible. European cool season grasses like Meadow Fescue, Italian Ryegrass, and Festulolium, warm season annuals like BMR sorghum sudan or BMR millet, and winter small grains like triticale can all fit this description if the right varieties and management are used. By increasing the amount of digestible fiber in our forages we can increase forage inclusion rates, lower intakes, and still maintain animal performance.
Daniel Olson is a 7th generation dairy farmer and the founder of Forage Innovations, a forage consulting company that help bring innovative forage systems and solutions to innovative dairy farmers in 24 states.
