Dr Liz Homer explains how the new Trouw Nutrition NutriOpt Dairy system can help improve how cows milk in future.
Two things are true about rationing dairy cows.
The first is dairy farmers, consultants, nutritionists or vets all want the same thing from a diet. We want cows to milk cost effectively, to get back in-calf quickly, to remain healthy and leave a significant margin.
The second is all rations are predictions, based on our understanding of the nutritional value of feeds and how those feeds will be utilised by cows. The better we can de- scribe feeds and how they are used by the cow, the more accurate our predictions will be and the more closely cows will perform as we expect.
Rationing systems attempt to pre- dict how feeds will be utilised in the cow – nothing more. What a cow will use to live and produce is not the feed she eats, but the end products of digestion which are absorbed after the feeds have been broken down.
This covers rumen fermentation and the action of trillions of micro-organisms on the feeds in the diet as well as digestion in the intestinal tract.
Previous rationing systems were not able to predict what end products of digestion an individual feed or combination of feeds would produce, and this is where NutriOpt Dairy is different. We now have a more accurate prediction of what the cow will actually be able to use and therefore how much she will be able to produce.
And together this means we can produce a more accurate ration in terms of energy, protein and rumen health. To do this, NutriOpt Dairy has developed some new terms which allow us to describe feeds and how they are used. While the basic components such as dry matter, crude protein, NDF and starch and sugars are still important, they do not accurately describe how feeds are used.
A good example of this is metabolisable energy (ME). While it is an estimate of the energy content in a feed, it is not a prediction of the end products of digestion and therefore the energy actually available. To improve the precision of diet formulation a new way of defining energy was needed.
This term is Dynamic Energy (DyNE), which is the sum of all the end products of digestion available including volatile fatty acids (VFAs) from rumen fermentation, digested bypass starch absorbed in the small intestine, and VFAs produced from fermentation in the large intestine.
As well as getting used to a new term, it will be important to become familiar with how much energy is required. As the table shows, the requirements for maintenance and per litre are lower than for ME, simply due to the fundamental differences in approach in the two systems.
Research shows rationing cows on DyNE can make a big difference as it more accurately assesses the energy actually available. Using nearly 20,000 grass silage samples we analysed last year, we found, on average, a cow eating 10kgDM/day of grass silage would receive enough energy for M+5 litres/day when rationed using the ME system, but M+7 litres when using NutriOpt Dairy and DyNE.
A similar benefit was seen when we looked at the top samples and the poorer silages, suggesting rationing using DyNE could have been worth about 400 litres more from forage per cow over a 200-day winter, which will make a big difference to margins.
However, not all forages resulted in increased milk yield, so it is important to know the exact analyses of your silages to improve the predictability of your ration’s performance. Dynamic energy will be reported on many silage analyses this winter, allowing you to develop more effective rations.
|Table 1||Feed in to milk||Nutriopt Dairy|
|Metabolisable Energy, MJ||Dynamic Energy, MJ|