Winter dairying

Right fibre content to slow feed’s passage

THE importance of getting the physical nature of diets correct this winter has been witnessed first hand by Mark Voss.

“Over the last few weeks, as cows have settled in on winter rations, a common observation has been feed is flying out of the cows and they just aren’t milking,” says Mr Voss, senior system specialist with Keenan.

“Closer inspection usually points to the same cause, forage quality and, more specifically, fibre levels in the diet.”

He says fibre, both the amount and type, is essential for efficient rumen fermentation by controlling the rate of feed passage through the rumen and the ability of the rumen bugs to harvest nutrients from the diet.

If you get fibre content right the effect will be to slow down rumen passage, reduce pH fluctuation and increase performance

Mark Voss

In many cases, this year’s grass silage is passing through cows very quickly. This may be because it is very leafy and low in fibre, says Mr Voss, or because it is wet and acidic, leading to an increased acid load in the rumen and acidotic conditions. He also believes the situation has been exacerbated by the maize analyses.

“Some farmers have been forced to take wet crops of maize, which has resulted in wetter acidic crops.

“The overall effect is food is being retained in the rumen for too short a time, leading to low nutrient recovery, something which is exacerbated by the high acid load in the rumen.”

Control

To improve performance, Mr Voss says it is important to control intakes and slow the rate of rumen passage down to give the rumen bugs time to do their job.

According to Mr Voss, there are three components to the solution. He advises farmers to look at the source of concentrates in the diet and include as many digestible fibre sources, as opposed to starch sources.

For example, he suggests replacing rolled cereals with a product like beet pulp to increase fibre levels and reduce acid loading.

The second component will be to include rumen buffers to help reduce pH, but by far the biggest component is to get a cow ‘back to being a cow’ and digesting more fibre from forages.

“Farmers need to get back to the basics of effective physical nutrition, which means delivering the correct distribution of particle sizes and fibre while ensuring the optimum bulk density.

Proportion

“We have seen good results this year where the proportion of fibre has been increased and where fibre sources have been mixed. A range of fibre sources is important to achieving better rumen stimulation.

He says there have also been good results from adding hay, which also improves diet palatability.

“Whichever fibre source you use it is vital it is chopped to the correct length, around 4-8cm, to retain its physical characteristics and it is effectively mixed into the diet.

“If you get fibre content right the effect will be to slow down rumen passage, reduce pH fluctuation and increase performance.”

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