Rumen health seminar: Unlocking the benefits of fibre

Key points

Ensuring cows have access to physical effective fibre and sufficient time to ruminate is essential for maintaining rumen function, animal health and productivity.

Lallemand Animal Nutrition Technical Services – Dairy, Tony Hall, says fibre is a key determinant of digestibility, rate of passage through the gastrointestinal tract and dry matter intake.

“Our number one goal is to make sure the ration is digestible in the animal,” he says.

“Digestibility liberates the energy in the ration for the animal that will contribute to milk production or improvements in body score and fertility.

“The second goal is to make sure the ration is palatable.

“Finally, we want to make sure the ration is hygienic and does not contain anything that’s going to make them sick, disrupt rumen function or steal nutrition that should be available for the cow.

“Digestibility, palatability and hygiene go hand-in-hand with good ensiling method – cutting at the right growth stage, using a strain specific inoculant, keeping oxygen out of the bunk and managing the face during feeding out.

“Good ensiling makes sure as much of the nutrients that were in the paddock are presented to the cow, reach the rumen and are digested, rather than being wasted along the way.”

Tony encourages producers to measure physically effective fibre rather than Neutral Detergent Fibre (NDF).

Physically effective NDF considers the physical characteristics of a feed, particularly particle size, that influence chewing activity, the production of saliva and the mixing of liquids and solids in the rumen.

“Physically effective NDF should represent at least two least two thirds of the total dietary NDF,” Tony says.

“Knowing the level of physically effective fibre allows you to replace a forage or roughage in the ration so that the percentage of milk fat produced is effectively maintained.”

Forage fibre particles greater than 1.18mm using a vertical separation test (Ro-tap sieve shaker) or greater than 4.0 mm using a horizontal separation test (Penn State shaker box) are considered physically effective.

“Even the simplest comparison of a fresh TMR or PMR before and after feeding shows that cows can easily sort ingredients by size,” Tony says.

“They don’t want to eat the long particles because they want to consume the most nutrients for least effort.

“Dry TMRs and PMRs are particularly prone to being sorted.

“Likewise, that’s why baled silage is not a great complement for PMR systems – your cows going to spend all day sorting out or chewing through the longer chop length.

“Everything is a trade-off.

“Coarse rations reduce DMI because the cow has to chew more when eating and is less efficient in terms of feed conversion.

“Processed rations increase DMI, rumen fermentation, acetate:propionate ratio and feed conversion efficiency – but can depress milk fat.”

Tony says one of the greatest benefits of intensive feeding systems is that it gives cows more time to do what they are designed to do – ruminate, especially while lying down!

“Digestibility and rate of passage are a delicate balance,” he says.

“Cows have to be able to digest forage – but they also need sufficient time to actually absorb that digested forage before it is passed.

“We want our cows to eat everything that is presented and then go lay down and chew the cud.

“Rumination, the process of turning the rumen over, gets the fatty acids mixed in and close to the rumen wall, where they can be absorbed.

“Grazing cows are really busy – they have to walk to and from the dairy, eat as much as they can, walk to water and then walk back to the dairy.

“They simply don’t have enough time to get everything done in a 24-hour block of time, particularly eating enough and ruminating.

“Providing a TMR or PMR feeds turn the table in your favour by maximising DMI.

“Cows eating a TMR can consume 50% more feed in half the time, which gives them 50% more time for ruminating or lying down.

“In effect, TMR-fed cows are eating for 4 or 5 hours a day instead of say, 9 to 11 hours a day.

“That’s an extra 5 or 6 hours when they could be ruminating, lying down, and making more milk component yield.”