This article was #22 of the Top 25 most well-read articles on www.progressivedairy.com in 2013. It was published in the July 11, 2013 Extra e-newsletter. Click here for the full list of the Top 25. The Four State Dairy Nutrition Conference held in Iowa in June 2013 featured a panel discussion on low-protein feeding. Wisconsin dairyman John Koepke, Cornell University’s Mike Van Amburgh, Nutritional Professional Inc.’s Steve Woodford and Purina Animal Nutrition’s Dave LaCount provided tips for making this feed strategy work.

We asked the panelists,
Q. What factors do you think will make low-protein feeding more widely accepted in the future?

A number of factors will drive lower protein rations in the future. Cost will be an important factor. If cows can produce the same or more milk and components on a lower-protein diet that costs less or results in a greater return on investment, dairy producers will adopt that technology.

As technological advances continue, better and more consistent sources of bypass amino acids will likely become available. As the technology improves, the consistency of the response in cows also will likely improve, which will lead to greater adoption of low-protein diets.

Finally, environmental concerns and regulations may force producers to minimize excess nitrogen in the environment. This will be best achieved by utilizing high-quality bypass protein sources and protected amino acids to feed low-crude protein diets. Ultimately, the combination of economics and environmental impact will result in widespread adoption of feeding low-protein diets.

— Dr. Dave LaCount, dairy nutrition and technical service manager, Purina Animal Nutrition

A greater adoption or implementation of “low protein diets” will depend on several factors. First, we need to get better at predicting the most limiting nutrients on a regular basis and once we have that, we need to be able to target the specific amino acids that are limiting relative to metabolizable energy allowable milk yield. We are getting better at predicting those and our next generation of nutrition models are going to be much better at this than we currently are.

When that happens, the discussion between the nutritionist and herd owner/feed manager will change and that will be the next biggest challenge. For example, as we get closer to predicting the absolute requirements for metabolizable protein and individual MP amino acids, feed variation and feeding management variation become a larger concern on a daily basis.

Thus, we will be able to put a cost to the “safety factor” of having to potentially overfeed protein to ensure that the amount fed never falls below the requirement due to the variation around the feed and feeding management.
—Mike Van Amburgh, Department of Animal Science, Cornell University

I would say based on my client feedback, the need to lower feed costs and comply with tighter nutrient management regulations will drive this. Once we demonstrate that we can lower ration protein without any production loss, it helps out on both fronts.

I think the difficulty is always convincing the client that we can do this. Good records are critical to evaluating animal performance to these ration changes. Once we show that, convincing the client we might be able to lower ration protein more becomes easier. PD

— Dr. Steve Woodford, nutritionist, Nutrition Professionals Inc.

ARTICLE:

A panel discussion on low-protein feeding of dairy cows offered various input at the Four State Dairy Nutrition and Management Conference held June 12 and 13 in Dubuque, Iowa.

Protein, a macronutrient, is comprised of nitrogen-containing groups called amino acids. Information, such as milk urea nitrogen (MUN), which allows the fine-tuning of the ration, is sought after since protein is often the most expensive component of a milking herd’s ration.

“As we learn to lower the overall nitrogen intake, amino acid supply and balance is much more important, and if the diet is at the limit of the metabolizable protein requirements, removing or not balancing for amino acids can have a significant and detrimental effect on milk protein," said Dr Mike Van Amburgh of Cornell University.

He added, “Also, we are not yet good at predicting which way the cow will partition the amino acid carbon, thus sometimes we see milk protein, milk fat or milk volume changes with the addition or subtraction of rumen-escape amino acids.”

Van Amburgh explained milk protein output is a function of supplying energy and amino acid balance. Most nitrogen in the cow’s urine results from excess feed nitrogen intake and urea nitrogen recycling, and it is variable.

High levels of urinary nitrogen indicate overfeeding total protein, and high rumen nitrogen balance relative to microbial demand. Further, urine nitrogen is volatile, so reducing it will reduce the environmental impact and improve efficiency of the cow.

Also, energy supply is the primary factor affecting milk protein output and overall protein efficiency.

Amino acid balance might enhance the efficiency of nitrogen use but not always directly. He said reducing the non-functional protein in the diet (which reduces urinary nitrogen excretion) and replacing that protein with escape protein and amino acids can be beneficial.

To best do this, balance the ration on energy-correct milk (ECM) to account for milk volume, protein or fat changes, Van Amburgh said.

“Ultimately, the key to low-protein feeding is a carbohydrate and energy issue,“ said Dr. Steve Woodford of Nutrition Professionals Inc.

Woodford said the thought process to low-protein rations should start with first looking at the amino acid balance using milk urea nitrogen (MUN) as the measurement. The goal should be in a target range of 8 to 10 milligrams per deciliter (mg/dl).

By lowering the protein in the ration producers should be able to offset the cost of amino acids.

“From this point on monitoring cow response is critical; I’m not sure models tell me when this works,” he said. “Previous rations were deficient in metabolized protein. Be sure to monitor the dry matter intake, tank milk and components and peak milk. The requirement for low-protein rations including multiple high-quality forages, multiple grain sources, digestibility and fecal starch data and good genetics.”

Dr. Dave LaCount, Purina Animal Nutrition, agrees it is important to use amino acid levels to balance rations.

He encourages nutritionists to work with what they have available on the farm and to formulate diets to achieve the best cost given the current economics.

LaCount said, “The common factors in a low crude protein diets that work for his clients are excellent corn silage, blood meal, high-bypass soybean meal such as Surepro, protected lysine in the form of USA Lysine, protected methionine."

He noted diets with a lot of corn silage and minimal amounts of alfalfa haylage favor lower crude protein.

“Bloodmeal can be used but know what you are dealing with,” LaCount added. “There are a lot of inconsistencies, but it’s not all bad.”

John Koepke, a dairy farmer from Oconomowoc, Wisconsin, who has a herd of 330 milking cows, recommends looking at the basics before analyzing amino acids.

“Reducing input variability by categorizing forages and targeting their use has made things even more successful, such as [feeding] top forages to top cows, etc.”

Koepke Farms has a rolling herd average of 29,858 pounds, 4.1 fat, 2.99 protein and a somatic cell count of 95,000.

He says he could lower the crude protein in the diet of his lactating cows by utilizing higher percentage corn silage, but “alfalfa is a very important part of our no-till crop rotation,” serving as a forage source, fertilizer for a following corn crop, erosion control, tillage tool and to reduce nitrogen loss at the field level.

Koepke recommends measuring nitrogen levels at the ration, bulk tank, manure spreader, waterways and tile line outlet to minimize environmental impact.

He feeds different crude protein levels for different rations. Cows less than 70 days fresh receive 16.8 percent crude protein, 70 to 200 days 15.7 percent CP and about 15 percent for the “low” herd.

“As always, watch and listen to the cows; they know better than we do,” Koepke asserted. “And when things are right with them, document what is going on and do your best just to keep out of their way."

Dr Mary Beth Hall, Research Animal Scientist with the U.S. Dairy Forage Research Center/USDA-ARS, pointed out during her presentation “Protein and carbohydrate interactions in the rumen” that more degradable protein relative to carbohydrate increases the energy efficiency of rumen microbes and potential nutrient supply to the cow.

“But, don’t overfeed protein!” she said. “Adjust timing for rapidly available protein relative to rapidly available carbohydrates. We still need to work out issues on passage of microbes from the rumen to make sure the cow benefits from more bug growth.”

When a cow is fed too much degradable protein relative to carbohydrates, the result is excessive ammonia production. If rumen microbes don’t have the energy from carbohydrate to use the ammonia, the liver converts it to urea and it can then be excreted in urine.

Making urea costs energy, so overfeeding protein reduces the amount of energy available to the cow to make milk, wastes feed protein and increases nitrogen excretion. PD

PHOTO
Low-protein feeding panelists included, left to right: John Koepke, Mike Van Amburgh, Steve Woodford and Dave LaCount. Photo by Kelli Kaderly-Boylen.

Kelli Kaderly-Boylen is a freelance writer based in Waterville, Iowa.