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by Tom Hough, NWF Technical Manager
Over the winter we have been developing a much greater understanding of rationing and what dairy cows actually require thanks to the new NWF RPM feed system. RPM has helped us be more precise about feeding and managing the rumen to ensure efficient digestion combined with high rumen health. It has also allowed us to consider the nutrients the cow herself requires for milk production.
When evaluating diets in this way, one aspect that has become clear is that many diets are short of 'metabolic glucose', also known as glucogenic energy, and this has a major effect on milk yields.
Glucose is required for the production of lactose in the udder. Under normal conditions, milk has a constant lactose concentration of typically around 4.6% for black and white cows. As more lactose is produced, more water is drawn into the udder and so milk yield increases. Therefore, if we can increase the supply of 'metabolic glucose' it should be possible to increase milk yields.
Clearly then, the diets of high yielding cows need to be high in glucogenic precursors, which are metabolised into glucose. There is a strong relationship between the supply of glucogenic precursors and milk yield.
The problem is that the main source of glucogenic energy is starch, either as starch fermented in the rumen or rumen by-pass starch. Increasing the total supply of starch might seem at first glance to be the way to increase the supply of glucose, but if too much of the starch is fermented in the rumen there is a risk of acidosis and reduced rumen function.
The rate and extent to which starches are degraded in the rumen varies from ingredient to ingredient and the aim is to increase the proportion of rumen by-pass starch in the diet.
The challenge was to find a way to cost-effectively increase the supply of metabolic glucose without causing problems in the rumen. The principal sources of starch in diets are cereals and maize. Ingredients like wheat have lower glucogenic values when compared to maize, but if the starch is protected to allow it to pass through the rumen, the supply of glucogenic precursors increases greatly.
This led us to develop Ultra Starch-W, a new feed ingredient available exclusively to NWF clients. Rolled wheat is treated at our Wardle site using the same process as used to protect proteins in Ultra Soy and Ultra Pro-R. The result is that a greater proportion of starch is able to pass through the rumen undegraded, in so doing increasing the supply of glucogenic precursors without placing rumen health at risk.
The process increases the supply of glucogenic nutrients in wheat by over 10% and makes wheat more comparable to maize, but Ultra Starch-W is a more cost effective solution, promoting higher glucose production to drive greater performance.