Change is not always an easy concept to embrace. But for dairy producers and nutritionists willing to look at their rations in a new light, getting in on the leading edge of change with amino acid balancing offers environmental rewards as well as benefits in herd performance. That’s because dairy diets have long been formulated to oversupply protein in hopes of delivering adequate levels of limiting amino acids. While certainly understandable in theory, this practice has its drawbacks. It is:
- Expensive – Protein is not cheap, especially when it is not always fully utilized by the cow.
- Inefficient – When cows are overfed protein, they use energy to get rid of the excess nitrogen, diminishing efficiency.
- Environmentally undesirable – Excess nutrients from overfeeding protein are excreted in manure and urine.
To help offset feed expenses and reduce environmental consequences, leading dairy producers and nutritionists are closely analyzing the negative impact of overfeeding protein.
Their evaluations have led them to implement the practice of amino acid balancing, which delivers the right amino acid profile to the dairy cow to complement rumen microbial protein (amino acid) synthesis to deliver optimal levels of lysine and methionine to the small intestine.
There are two main advantages of amino acid balancing, explains Dr. Cornelius de Lange, a professor in the University of Guelph’s Department of Animal and Poultry Science with years of experience with balancing swine rations for amino acids:
1. It reduces the amount of excess dietary protein, thereby reducing nitrogen excretion in urine and feces and its potential negative impact of animal production on the environment.
2. It allows for more extensive use of alternative protein sources in diets, allowing reductions in feed cost while maintaining the animal’s productivity.
Research shows that on many farms there is an opportunity to lower ration crude protein by 0.5 to 1.5 percentage points without sacrificing production or health.
Amino acid balancing in action
Improved ration balancing software led Todd Follendorf, consulting nutritionist with Ag Consulting Team based in Dane, Wisconsin, to try amino acid balancing several years ago, enabling him to “ratchet back ration crude protein levels” for a number of dairy clients.
He began by introducing fish meal or blood meal to rations about six or seven years ago, but when fish meal prices suddenly climbed and concerns about the high variability of blood meal surfaced, he switched to commercial sources of bypass amino acids that were much more consistent and cost-effective.
“I’ve lowered crude protein in my customers’ lactating rations by more than a point,” he explains. “It’s a learning process that’s still evolving. We haven’t gone down as far as we can go, but we’re getting there.”
Meanwhile, cows have reacted favorably to the rations. “We’re going by what the cows tell us,” says Follendorf, “and they’ve maintained milk fat production, even over the course of warmer weather, and milk protein levels have shown improvement.”
A cue from swine and poultry diets
While fairly new to dairy producers, the concept of amino acid balancing has been in use in diets for other species for some time.
Poultry led the way in the 1970s and commercial swine rations have been balanced for amino acids for more than 20 years. Now, almost 100 percent of swine and poultry diets are formulated to deliver optimal levels of limiting amino acids, says Dr. Mike Tokach, animal science professor at Kansas State University .
“There are still some swine producers and nutritionists using total amino acid values, but the vast majority use digestible amino acids to be more accurate with their formulas and to ensure they are meeting the animal’s body requirements,” he adds. “Without the availability of manufactured amino acids used, the average diet would probably be 3 to 4 percent higher in crude protein than it is today.”
This success demonstrates the window of opportunity available as dairy producers and nutritionists work to fine-tune dairy rations.
While amino acid balancing benefits animal performance, it also has a significant effect on the environment due to the fact that when you reduce excess dietary protein, the amount of nitrogen excreted also decreases.
The excess nitrogen is excreted in feces and urine, with urine nitrogen (which is highly variable) being converted to ammonia.
Both fecal and urinary nitrogen excretion are reduced when rumen escape amino acids replace intact protein – like soybean meal – in the diet; however, urinary nitrogen is reduced to a greater extent, says Tokach. In turn, this reduces volatile ammonia emissions.
Research shows that when commercially available amino acids are used in swine diet formulation, nitrogen excretion is reduced approximately 10 percent for each percentage point reduction in dietary crude protein.
Ultimately dietary nitrogen reductions may change nutrient management practices, like the amount of land needed for manure applications.
For dairy cattle, a primary way to lower ammonia emissions is to balance rations to meet, but not exceed, the cow’s requirement for metabolizable protein and the rumen’s requirement for degradable protein. It’s been estimated that a one-unit decrease in ration crude protein to 16 percent will lower ammonia emissions by 20 percent.
“The environmental benefit of amino acid balancing is a great story for the dairy industry to tell,” notes Follendorf. PD
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Nitrogen metabolism explained
Even though nitrogen metabolism in the dairy cow seems complex, it can be broken down to a few key points, say researchers at Cornell University .
Essentially, it comes down to this: Nitrogen consumed in feed is either used as a nutrient source to support body growth and maintenance and for milk and milk protein production, or it is excreted via urine and feces.
Milk nitrogen efficiency is one index that can be used to assess the efficiency of nitrogen use in the dairy cow.
This index is simply the ratio of the quantity of nitrogen in milk divided by the quantity of feed nitrogen consumed.
This value in commercial dairy herds usually ranges between 20 and 35 percent, implying that 65 to 80 percent of the nitrogen consumed is excreted.
As ration crude protein increases, the milk nitrogen efficiency value tends to decrease, which benefits neither the cow, a farm’s bottom line nor the environment. Conversely, the opposite is also true.
“We have lots of opportunities to improve nitrogen efficiency of the dairy cow,” says Dr. Mike Van Amburgh, associate professor of animal science at Cornell University. “Theoretically, we should be able to double current efficiencies.
On a more practical basis, there are herds and high-cow groups attaining 38 to 40 percent efficiency, which can be emulated through amino acid balancing and modeling approaches with the availablility of highly digestible forages.”