Understanding fibre to mazimise value of forage

Oct 18, 2019

With good silage stocks and most clamps containing high quality feeds, there is a great opportunity this winter to produce more from forage and reduce feed costs per litre.  Roy Eastlake from Lallemand Animal Nutrition says that key to this will be maximising intakes and to do this you need to understand fibre.

Fibre plays a central role in milk production and the utilisation of forages, influencing rumen function and regulating total dry matter intakes.  What you need to be producing are forages with high levels of digestible fibre.

When your forages are analysed the fibre fraction is usually described as Neutral Detergent Fibre (NDF) and lignin. Some analyses are now also reporting digestible NDF (NDFd), which is a better indicator of the digestibility and therefore value of the fibre.

Fibre digestibility is important as it affects the rate of fermentation in the rumen, the rate of rumen passage and ultimately dry matter intakes. More digestible fibre will be fermented faster in the rumen, stimulating higher intakes. Indigestible fibre sits in the rumen and can depress appetite.

Balancing fibre

We need to maximise NDFd whilst balancing the level of undigested fibre to increase dry matter intakes and feed efficiency.  For example, young grazed grass is very high in NDFd and contains little undigested fibre so passing through the rumen quickly and increasing dry matter intakes.  At the other extreme, high straw diets for dry cows are more lignified and  contain a much higher level of undigested NDF, so passing more slowely through the rumen and reducing dry matter intakes but maintaining a higher rumen fill.

Another factor to take into account to maximise rumen health is the effectiveness of that fibre at forming a rumen mat to stimulate rumination. Optimising rumination is essential to maintain high production levels and a healthy rumen environment. Physically effective Neutral Detergent Fibre (peNDF) is the proportion of fibre that stimulates cudding and the formation of a functional rumen mat. It can be measured in most diets by sieving with a Penn State separator.

While on average silages have analysed well this year, we are seeing generally higher lignin content which is a bad thing as lignin is indigestible, causing lower intakes.  Where lignin is high, the rumen will need to be supplemented with the optimum level of rapidly fermentable energy sources but these can increase the risk of acidosis.

To improve fibre digestion and stabilise the rumen environment where higher levels of rapidly fermentable cereals have to be fed, feeding the proven rumen specific live yeast, Levucell SC has been shown to increase both milk production and feed efficiency in numerous independent trials.

By understanding fibre better you should be able to maximise the contribution from forage this winter.