Forage fiber plays an important role in the ration, says Mike Allen, dairy nutritionist with Michigan State University.
Forage slows the rate that cows eat, thereby preventing slug feeding, he says. “This is particularly important in group-housed situations where there’s limited bunk space, but it’s important for most other situations as well.”
Forage fiber also is extremely important for forming the rumen mat. “The rumen mat entraps small feed particles and that increases digestibility and the efficiency of conversion of feed to milk,” Allen says.
It also increases digesta mass and volume. “Greater digesta mass and volume is beneficial because it reduces the risk of DAs (displaced abomasum) and reduces the risk of acidosis or low ruminal pH (because it provides buffer),” Allen says.
"With greater pH we see greater fiber digestibility and reduced milk fat depression," he said during a recent webinar hosted by Dairy Herd Management.
Greater digesta in the rumen increases pH three different ways: 1) It stimulates mixing and absorption of acids from the rumen, 2) it buffers directly and 3) it stimulates chewing and saliva flow.
However, the downside of a more filling diet is it can limit feed intake and milk yield. During the web seminar, Allen presented data showing that as forage neutral detergent fiber (NDF) concentrations increase, intakes go down. This is why Allen advocates using forages with lower NDF concentrations when feeding a high-forage diet.
Data also show that the milk production of high-producing cows responds positively to a lower forage NDF concentration. The response is linear with level of milk yield, Allen says, so as milk yield increases, the response will be greater.
"Forage NDF is very important for how cows respond to the diet," Allen says.
To learn more about forage fiber concentration and its role in high-forage diets, click here.