Sep 20, 2014
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Calibrate Technologies

RSS By: Margaret Winsryg, Dairy Today

Margaret Winsryg is a technical support specialist with Calibrate® Technology. Margaret holds a Bachelor’s Degree in animal health science, a Master’s Degree in ruminant nutrition from the University of Arizona, and a Ph.D. in animal science nutrition from Utah State University.

Use digestibility testing to manage challenging forage supplies

Oct 07, 2013

 Many dairy producers face a lack of forage or poor-quality forage supplies this year. Given these less-than-ideal circumstances, it’s imperative to know what you’re dealing with in order to avoid negative consequences on milk production.


Traditionally, nutritionists have looked to crude neutral detergent fiber (NDF) to tell them more about a farm’s current forage supplies. However, we’re learning that it’s actually NDF digestibility that is the more important factor to consider when faced with a forage challenge.


If forages are slow to digest, the rumen will have a high fill potential, meaning more undigested forage will accumulate in the rumen. If forages digest quickly, the fill rate will be low and less forage will accumulate in the rumen. Both of these situations - fast or slow fiber digestion - can have an impact on feed intake, milk production and feed efficiency.


NDF digestibility testing is a way to gain insight into the speed at which forages are digested in the rumen. This information can help you be more efficient with current forage quality and supplies.


If a cow consumes a diet containing forages with low NDF digestibility, she will eat less because the passage through the rumen will be slower. Digestion of the feed ingredients will be higher and feed efficiency will be increased. However, if the low NDF digestibility has not been accounted for, milk production may drop off. In this situation, if you know the NDF digestibility is too low, you can remove forage from the diet and replace it with purchased ingredients to maintain intakes and milk production.


Conversely, when forages are in tight supply or feed ingredients are limited you can add less digestible forages to the ration to fill up the rumen, slow down the rate of passage, increasing digestibility and feed efficiency of the diet.


It’s a balancing act between available forages, fiber digestibility and managing feed costs, but knowledge gained from NDF digestibility testing can help you optimize fiber in the ration when you’re faced with a forage challenge.

Harvest delays hurt fiber digestibility

Oct 04, 2013

 Many dairy producers and nutritionists are looking to higher forage diets to help them reduce feed costs. Lactating-cow diets that previously contained 45 to 50 percent forage are now being formulated to contain 60 percent or more forage.

To accommodate this shift to a higher forage diet, you may be tempted to delay forage harvest to increase tonnage per acre. Although more forage will be available, the maturity of that forage also will be greater. As forage maturity advances, neutral detergent fiber (NDF) digestibility decreases. If forages make up a significant portion of the diet, the lower NDF digestibility could depress feed intake by slowing the rate of passage.


Conversely, a cow consuming a diet with higher NDF digestibility will have lower rumen "fill" or undigested NDF. Less rumen fill means there is a higher rate of passage of feed ingredients through the rumen and this supports higher dry matter intake.


Digestibility testing gives you a better understanding of NDF digestibility in the rumen. You can put this data to use to optimize dry matter intakes, feed efficiency and milk production.


Ultimately, you must balance the advantage of increased tonnage with your farm’s milk production goals. Make a plan for the forages you intend to grow and how harvest dates will impact the digestibility of NDF in those forages when it comes time to feed them to the cows.


Many dairy producers and nutritionists want to feed more forages in order to reduce feed costs. If you choose to go this route, use the knowledge gained from NDF digestibility testing to optimize fiber in your rations.




Dealing with the transition to new silage

Oct 03, 2013

 Starch can play a major role in your cows’ performance. This is certainly true when it comes to feeding new-crop corn silage. It’s common in these situations to see a drop in milk production, even though the ration formula has not changed. The origin of the problem can often come down to starch variability in the corn silage itself, as well as variability in the starch available to the rumen microorganisms.


Crude starch and rumen digestible starch are two ways to measure starch levels in the diet. Crude starch measures how much starch is present in the feed. Rumen digestible starch gives you an idea of how much starch is actually available to the rumen microorganisms. Knowing this is valuable for managing the effects of switching to new-crop corn silage.


For example, if rumen digestible starch scores from the new-crop corn silage show it is lower than starch scores from the previous crop, you can expect the starch to be less available in the rumen and to the cow. Cows respond to lower rumen digestible starch by producing less milk and higher components. The lower production response associated with switching to the new silage can last one to two months.


However, if you test for starch digestibility before feeding the new crop, you know what you’re up against and can take action accordingly. If you find yourself with low scores, you can try leaving the new corn silage in storage longer. Over time, starch availability of stored corn silage improves. Or, you might try replacing the corn silage starch with a feedstuff that has greater rumen digestibility or higher starch content.


Remember, starch availability can vary significantly from year to year, but when you make ration changes with consideration to rumen digestible starch it can help you keep rations consistent and avoid hiccups in your cows’ performance.

Go beyond crude starch

Oct 02, 2013

 The starch content of feeds can often be quite variable.


A look at corn silage samples collected from across the U.S. over a five-year period between 2007 and 2012 shows crude starch varied from 2 percent to 58 percent with an average of 30 percent.[1]


While this is problematic on several fronts, it gets more complicated. That’s because the starch available to rumen microorganisms also can be inconsistent, and that means the starch available to the cow also will be variable.


During the same five-year period, rumen digestible starch scores of corn silage samples ranged from 1 to 10.3 with an average of 7.8. A low score indicates the starch is slow-digesting. A high score indicates a fast-digesting starch.


Variability in the starch available to the cow can be problematic to performance. On one hand, excessive amounts of digestible starch can have negative consequences on fiber digestibility in the rumen, as well as energy metabolism, dry matter intake and milk and milk fat production. On the other hand, if starch is less available in the rumen, it will not adequately support propionic acid production in the rumen. Ultimately, this has ramifications on lactose synthesis, which has a direct impact on milk production.


Keeping the pendulum from swinging too far in either direction can be a challenge. Fortunately there is help for managing the effects of starch variability, but it involves more than simply knowing and adjusting for crude starch levels in a feed. It also involves unlocking what’s going on with starch in the rumen.


Relying solely on the crude starch content of ingredients to formulate rations is simply not enough anymore. You need an accurate, predictable estimate of how degradable starch and fiber are in the rumen. Testing for rumen digestible starch and fiber gives you the knowledge to make ration decisions more effectively.

[1] In vitro ruminal digestibility of starch from corn silage samples collected across the U.S. varies both within and among years. Data from Calibrate® Technology Lab, 2013, Gray Summit, MO


Take feed testing to a new level

Oct 01, 2013

A number of traditional lab tests exist to help you analyze the nutritional value of forages and other key ingredients in dairy diets.


For example, it’s customary for nutritionists to submit forage samples for a crude protein analysis or to request the starch and fiber levels of a particular feed. Nutritionists and dairy producers turn to these values to help them formulate diets and make decisions that will help them boost intakes and milk yield.


While knowing these values is important to ration management, it’s time to kick feed testing up a notch and monitor not only the nutrient content of feedstuffs in the ration, but also how well the rumen digests those nutrients.


Knowing the ruminal digestibility of key nutrients, like starch and fiber, offers several advantages.


A rumen digestible starch test estimates how much starch is present in a feed like corn silage, and takes it one step further by estimating how degradable that starch is so you have a better idea of how available it is to the cow. This is powerful information for managing your rations.


For example, if rumen digestible starch testing reveals that one or more starch sources in the ration is low, it can be both safe and desirable to increase dietary starch levels.


Fiber digestibility testing also is advantageous to ration decision-making, particularly when you are feeding a high-forage diet. Customarily, a high-forage diet could have a lower energy density. However, this diet can still address many dairy objectives such as increasing feed efficiency especially in the late lactation cows and possibly growing heifers. If forage is going to be short in supply this year, knowing the digestibility of that fiber can help address those shortages.


Take feed testing to the next level. Know the ruminal digestibility of key nutrients like starch and fiber and use that knowledge to enhance existing diets and unlock opportunities to get more milk from your cows.

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