We offer some practical tips and pointers on optimising rumen function to make the most of this year’s ‘challenging’ silages, and to maximise intakes and cow performance
Driving rumen efficiency will be key to making the best use of diets this winter, driving production and margins while contributing cost-effectively to reducing emissions. So says molasses blends specialist ED&F Man’s Georgina Chapman. “Focusing on fine-tuning the rumen ensures that cows can make better use of the feed in their ration, and producers can reduce the need to add expensive ingredients and costs,” she explains.
“The role of the rumen is to take feed ingredients and, through microbial fermentation, turn them into nutrients that are required and can be used by the cow. A more efficient rumen will digest feeds more effectively and quickly, allowing increased nutrient uptake by the cow and driving performance. This will also help to reduce nutrient wastage and inefficiencies and is the most important first step in reducing methane emissions,” she adds.
A clear example of this is fibre, which the rumen microbes digest to produce the volatile fatty acids (VFAs) that are a major energy source to the cow. “An efficient rumen turns a low-value nutrient, such as fibre, into something the cow can utilise,” adds Ms Chapman. “The same is true for protein. Cows do not utilise crude protein per se. They need metabolisable protein, a major and important component of which is microbial protein produced by rumen fermentation.
“If the rumen is more efficient, the supply of microbial protein will increase and this can, in turn, actually allow overall crude protein in the diet to be reduced.” A more efficient rumen will increase nutrient capture from the diet but can also increase total nutrient intake by stimulating higher dry matter intakes. If the rumen microbes are balanced and working effectively, the rate of fibre digestion will be higher and the rate of rumen outflow will increase promoting higher dry matter intakes. “The economic benefits of a more efficient rumen supplying more nutrients to the cow can be huge, reducing the requirements for supplementary energy and protein, leading to lower feed costs and improving nitrogen use efficiency.”
Challenging silages
Ms Chapman says early indications show that this year’s silages are proving to be a challenge on many units, with cows struggling to achieve the necessary intakes and to then digest the higher fibre material. Consequently the nutrients in the fibre are not being released, reducing the supply of VFAs and microbial protein. Rumen outflow rates are reduced, depressing dry matter intakes, and a higher proportion of undigested feeds are being seen in the dung.
“We are also hearing reports of changes in cow behaviour, with cows making fewer trips to the feed trough, eating less and spending more time lying down trying to digest the diet,” says Ms Chapman. “Normal cow behaviour is to eat, lie down to digest the feed and then, once digested, she will feel hungry, get up and feed again. This year the urge to get up and eat is reduced because the rumen is still trying to digest the ration.”
She says the quickest ways to assess rumen function are to watch cows and to sieve dung on a weekly basis and assess the effectiveness of diet digestion. “If necessary take steps to modify the diet to improve rumen function.” Ms Chapman adds that to promote optimum rumen efficiency it is important to balance the supply of rapidly and total rumen-fermentable energy and rapidly and total rumen-degradable protein while, at the same time, ensuring the acid load in the diet does not increase. This can tip cows into SARA and acidosis.
Sugars are an important source of rapidly fermented carbohydrate, mostly fermented within two to three hours of feeding. Promoting a more active fermentation helps to increase fibre digestion, as well as microbial protein production and rumen throughput, which can help
stimulate dry matter intakes.
“By increasing sugar levels in the diet to between 6% and 8% while holding overall starch and sugar at between 28% and 32%, we can create a more efficient fermentation without increasing the acidosis risk,” she explains.
