Regular analysis is key to unlocking potential

2 February 2021

Test and monitor starch degradability in maize silages to feed more balanced dairy rations and maximise performance.

Producers should analyse maize silage regularly to keep track of starch degradability and to ensure optimum rumen health. So says Trouw Nutrition GB’s Liz Homer, adding that it’s the only way to guarantee cost-effective performance. ““This winter, with many grass silages offering lower digestibility, we have seen herds where diets have needed more rapidly fermentable carbohydrate to fire up the rumen – perhaps by adding cereals or molasses.

Fermentable energy

“Many producers were hoping that the addition of maize silage would provide the fermentable energy required for milking rations, to save on feed costs, but this has not been the case due to a lower starch content and reduced starch digestibility,” explains Dr Homer.

The latest analysis of more than 3,500 samples carried out by Trouw Nutrition confirm that while early crops analysed well, later harvested crops have lower D value, reduced ME content and lower starch. Starch degradability, which influences how well cows will make use of the starch, is lower and this is reflected in increased bypass starch. NDF and lignin are also higher.

“The result is a less fermentable crop with lower total and rapidly fermentable carbohydrates, which will have an impact on supplementary feed choices. One positive is that the acid load will be reduced, improving rumen health. And this means that it will be possible to increase fermentable energy sources if required,” she adds.

Dr Homer stresses that producers should not just assume maize is high energy and high starch, and advises regular silage analysis and balancing the diet accordingly. She adds that it is quite likely that, where crops have had less time in the clamp, diets will benefit from an increase in fermentable energy sources to optimise rumen efficiency.

“The starting point for all cost-effective diets is to optimise rumen function by balancing the types of carbohydrates and proteins. Where cows are underperforming, adding more bypass energy and protein sources may not be economic because they will not address the root cause of the problem, which is reduced rumen fermentation.

“This position may change as the fermentability of maize starch increases with time in the clamp, but there is no rule of thumb for how quickly this will happen or the extent of the increase.”

Research shows that any increase in fermentability results from the breakdown of the protein matrix encasing the starch granules. This typically affects diet performance three months after ensiling by making more starch available for rumen fermentation. Increases are usually greater in drier silages compared to lower dry matter crops, where any changes will be smaller and more gradual.

Monthly analysis

Dr Homer says the only way to get a handle on the degradability of starch in maize is regular monthly analysis to allow diets to be fine-tuned. Cow diets should then be formulated using the NutriOpt Dairy system, which is the only rationing system to ration cows based on the end products of digestion and takes full account of differing rates of rumen fermentation.

“Unless the rumen is balanced in nutrient terms and the rate of fermentation, cows will not perform as expected,” she continues. “Basing diets on regular analyses that include the details to understand exactly how silages, particularly maize, will perform in the diet means it will be possible to formulate rations for more cost-effective performance.”