Farmers look to molasses to bring feed rations up to scratch
Looking more closely at dietary sugars will help unlock the value in this year’s silages. British Dairying investigates how farmers and nutritionists can promote more efficient rumen function and hedge against variable forage quality this autumn and winter.
As cows begin to be housed onto winter diets, farmers and nutritionists are facing up to some specific challenges. Rations are having to be formulated to make the most of variable quality grass silages, although quantities appear to be good.
Feed ingredients markets look likely to remain volatile, fuelled by the continuing events in Ukraine and the poorer UK grain harvesting conditions. Finally, milk prices seem unlikely to improve over the winter months, putting downward pressure on margins.
“There is no doubt that rations will need careful balancing to ensure cows can maximise forage intakes and then get the most from that forage,” comments Georgina Chapman at molasses blend specialist ED&F Man. “The good news is that we know enough to help tackle the specific characteristics of this year’s forages and build effective diets.”
Data from Trouw Nutrition shows that grass silages are reasonable quality but reflect the mild winter, with a higher proportion of over-wintered grass (figure one). Second cuts were affected by the wet summer, leading to a proportion of more mature crops.
Overall energy levels are slightly reduced and sugar levels are significantly lower. Lignin levels are higher, which will affect digestibility, while rumen fermentable carbohydrates and proteins are also reduced. “Many of the challenges when feeding this years silages can be tackled by looking closely at the sugar levels in the diet,” says Georgina. “Adding sugars, in the form of a molasses blend can help improve fibre digestion, which will release more of the nutrients in forage, while also improving the palatability of the ration to stimulate intakes.
“Sugars will also stimulate microbial production and supply rumen fermentable carbohydrates without the risk of sub-acute rumen acidosis (SARA), and can increase dry matter intake without causing rumen fill,
due to the unique low substitution effect of a liquid feed.” Most UK diets are typically around 2% sugars in the dry matter, but this is significantly below requirements. Early lactation cows require 6% sugars, while cows at peak require 8%. Even late lactation animals need 6% sugar in the diet, she notes.
“Filling this sugar gap provides cows with valuable rumen fermentable carbohydrates to fuel the rumen micro-organisms, which will encourage better feed efficiency’
Fibre is a crucial source of energy but when lignin and neutral detergent fibre levels are high, this energy is more difficult to extract. Any fibre that is undigested is excreted, wasting potential energy. “By stimulating the rumen microorganisms, sugars fuel higher levels of fibre digestion.”
The photo (below right) compares dung sieving from a herd where dietary sugar level was increased from 3% to 6% by adding a molasses blend to the diet. After six weeks, the outcome was a 17% increase in fibre digestion with significantly less in the top sieves, a clear sign that the cows are using the diet better.
“Adding the optimal level of sugars in the diet also influences rumen fermentation in two significant ways.