Many dairy producers face a lack of forage or poor-quality forage supplies this year. Given these less-than-ideal circumstances, it’s imperative to know what you’re dealing with in order to avoid negative consequences on milk production.
Traditionally, nutritionists have looked to crude neutral detergent fiber (NDF) to tell them more about a farm’s current forage supplies. However, we’re learning that it’s actually NDF digestibility that is the more important factor to consider when faced with a forage challenge.
If forages are slow to digest, the rumen will have a high fill potential, meaning more undigested forage will accumulate in the rumen. If forages digest quickly, the fill rate will be low and less forage will accumulate in the rumen. Both of these situations - fast or slow fiber digestion - can have an impact on feed intake, milk production and feed efficiency.
NDF digestibility testing is a way to gain insight into the speed at which forages are digested in the rumen. This information can help you be more efficient with current forage quality and supplies.
If a cow consumes a diet containing forages with low NDF digestibility, she will eat less because the passage through the rumen will be slower. Digestion of the feed ingredients will be higher and feed efficiency will be increased. However, if the low NDF digestibility has not been accounted for, milk production may drop off. In this situation, if you know the NDF digestibility is too low, you can remove forage from the diet and replace it with purchased ingredients to maintain intakes and milk production.
Conversely, when forages are in tight supply or feed ingredients are limited you can add less digestible forages to the ration to fill up the rumen, slow down the rate of passage, increasing digestibility and feed efficiency of the diet.
It’s a balancing act between available forages, fiber digestibility and managing feed costs, but knowledge gained from NDF digestibility testing can help you optimize fiber in the ration when you’re faced with a forage challenge.