Formulating effective diets this winter will require a precise approach with particular focus on the impact on the rumen, particularly if specially created forage extender blends are being considered.

With the forage shortage intensified by the drought and the early opening of clamps, many farmers are looking for options to keep cows milking this winter. Dr Liz Homer, ruminant technical development manager with Trouw Nutrition says that it is going to be essential to make sure that rations are formulated to optimise rumen health and performance, but admits it will be a challenge.

“With carry over stocks low after the delayed turned out, farmers were in need of a good forage producing season but this hasn’t been the case with variable first and second cuts. It is anyone’s guess what third and subsequent cuts will produce," she said.

“The acreage of cereals cut for wholecrop has increased significantly and while the maize harvest will be earlier which could allow maize to be included in diets sooner, it will not increase the quantity produced."

Dr Homer said the skill is going to revolve around accurately assessing silage stocks and budgeting to ensure forages last through until turn out, even if this means reducing intakes per day. A dry autumn may help preserve feedstocks by allowing some livestock to graze longer or possibly to be kept out on fodder crops.

It will then be essential to make optimum use of available forage and to ensure that supplementary feeds allow the diet to fully meet the cow’s requirements.

The supply of many supplementary feeds is already tight and prices have increased accordingly. Distillers dark grains are unavailable, and there is limited sugar beet available. While a greater proportion of the straw crop is being baled this year, prices remain high. Fibre sources to maintain levels in the diet are in short supply.

In response to this situation, many feed suppliers are formulating forage extender blends and while they certainly have a place, Dr Homer says it is important to understand what they are designed to do and the impact they may have on the total diet.

She said: “Forage extender blends are being developed to promote fibre, fill and rumen function, containing combinations of ingredients such as wheat feed, soya hulls, straw, urea and molasses. They are being formulated as a higher fibre, moderate energy blend with more slowly fermented carbohydrate although the precise way they behave in the rumen will depend on the proportion of ingredients included. Generally they are low protein, typically around 16%.

“Typically substitution rates are expected to be 4kg silage dry matter for 4kgDM from a forage extender."

Dr Homer stresses it is vital to look beyond the headline ME and crude protein values and to understand the implications for nutrient supply from the total ration, particularly with regard to rumen health. Don’t expect the rumen to function as normal if forage intakes are reduced.

She says the inclusion of more slowly fermented fibre sources like straw and soya hulls could have an impact on rumen fermentation and the effective digestion of fibre.

“The rumen needs a supply of rapidly fermented carbohydrates (RFC) sources like ground wheat or barley to supply the rumen microbial population. A shortage will reduce fibre digestion and also lead to lower glucogenic energy supply which will have a negative impact on both fertility in early lactation and milk production.

Due to wheat being more expensive than maize this season, many feed compounders will be looking to swap raw materials. Although on the surface starch and energy levels may appear higher when you exchange maize for wheat, they behave differently in the rumen.

Wheat is more rumen fermentable than maize, but maize has a lower acid load and much higher bypass starch and glucogenic energy. So it is important to consider what is needed in the total ration to balance forages.

“If RFC are low, one solution could be to increase molasses up to 1kg/cow/day in the total diet to support fibre digestion by balancing sources of rapid and slow fermentable carbohydrates and proteins in the rumen, and boost glucogenic energy supply.”

She also warns that the inclusion of urea can affect the balance of energy and protein in the rumen by increasing the supply of rumen fermentable protein. She advises assessing the balance of rapidly and slowly fermented protein. If possible, and if prices are favourable, consider feeding more bypass proteins like soya to balance forage extenders.

“Forage extender blends can play a crucial role this winter on many businesses,” she continues. “However, it will be really important to know the precise formulation of the extender blend and to understand the impact on the formulation of the total diet. You can then fine tune the diet to promote optimum rumen performance.

She added that it is also important to bear in mind the effect of including blend in place of forages on overall diet dry matter. The target for a TMR is 50%DM. Including a blend at around 85%DM in place of a forage at say 35%DM could make diets too dry so it may be necessary to add water to reduce overall dry matters.