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What tools do we have to properly balance diets?

Dan Luchini Published on 19 September 2012

Engineers had the slide rule. Nutritionists used Pearson’s Square to calculate the proper inclusion rates for two ingredients in order to achieve the desired concentration of a single nutrient.

A lot has changed since those days. Yet dairymen continue to maximize production efficiency by using the forages and feedstuffs on hand and making wise feed purchases. Diets must supply minerals, vitamins, fatty acids, amino acids, carbohydrates and water.

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Some of these are essential and must be included in diets to avoid a deficiency. The perfect diet, then, would provide all the nutrients the cow needs to maximize production and health.

The field nutritionist’s goal is to have the right diet fed to the right cows at the right time. Each cow has specific nutritional requirements depending upon her stage of lactation. In other words, designing diets gets complicated quickly. Likewise, designing the perfect ration solely using Pearson’s Square is virtually impossible.

Fortunately, the advent of the personal computer encouraged development of several nutrition software programs. Now thousands of complex calculations can be done almost instantly.

Estimating the nutrient output of a ration based on several feed ingredients takes little time. The ultimate goal, however, remains formulating a ration that provides the right nutrients at the right time.

In North America, the vast majority of software programs used by nutritionists are based on two different biologies: those of the National Research Council (NRC) and the Cornell-Penn-Minor (CPM) program.

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Developed in the late 1990s, both serve as the basis for several commercial programs. Furthermore, some programs formulate least-cost diets by also calculating feedstuffs usage for the lowest-cost rations.

Are we there yet?
Despite having a great deal of scientific knowledge regarding the cow’s needs and advanced computer technology, we must recognize that no nutrition program is flawless. Having the perfect diet on paper does not necessarily translate into on-farm success.

The cows must consume the diet as formulated. Yet many steps exist between the paper and the cow’s mouth. No matter how good the diet formulation, the feedstuffs must be mixed and fed correctly. Software programs are not perfect, and management practices are not implemented the same every time, every day.

What is important is performing each step better than the day before. We are not there yet, but considering the tools we had 20 years ago, we have come a long way.

AA balancing
Each year more cows’ diets are being balanced for amino acids (AA). That doesn’t happen by chance. In the last 40 or 50 years, researchers from around the world have gained incredible insights regarding the cow’s specific amino acid requirements for maximum milk production and composition.

Early on, the complex calculations made it virtually impossible to use industry knowledge under practical situations. Then computers streamlined the science and math. Now the grams of AA available to the cow from feed ingredients in the diet can be estimated with tremendous accuracy.

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The research that demonstrated the benefits of AA feeding brought to light how milk production and composition are limited by the lack of proper AA balance in the diet. We now know that methionine (Met) and lysine (Lys), the first two most limiting AA in North America, have to be available in a specific ratio.

Today’s increased interest in balancing diets for Met and Lys results from three factors: focused research, advances in ration formulation software and implementation of the U.S. Federal Milk Marketing Order (FMMO) pricing system in 2000.

Most AA research focused on showing the impact of feeding Lys and Met on milk volume and composition and to maximize the efficiency of the diet’s nitrogen utilization. The nitrogen load of the diets for lactating cows has been decreasing steadily.

Not long ago, feeding a diet with less than 18 percent crude protein was inconceivable. Now, high-producing herds receiving less than 17 percent crude protein are common. Diets, however, must provide the right grams of Met and Lys to keep the cow healthy and expressing her genetic potential.

We’re on the right path
Cows require grams of Met and Lys in a specific ratio. If they are out of synch, waste is the result. Therefore, nutritionists often talk about the Lys-to-Met ratio. That relationship, originally determined by researchers in the European Union and U.S., was set at 3-to-1 (Lys:Met).

In time, with new discoveries and improvements in the software biologies, the Lys:Met relationship has been readjusted to values lower than 3-to-1. Yet, in the U.S., the Lys:Met of the vast majority of the diets is greater than 3, suggesting that most diets are low in Met.

However, even at a Lys:Met ratio greater than 3, the diet can be low in the Lys grams needed by the cow. Therefore, nutritionists must look at both the Lys:Met ratio and the grams of each.

What’s next?
Even though we focus on the first two most limiting AA, other AA will eventually limit the cow’s production. Here’s the challenge. Once feed enters the rumen, rumen microbes begin using the AA for their own needs. The AA must reach the small intestine intact to be used by the cow.

Several technologies currently protect AA. The important issue in evaluating a commercially protected Met or Lys product is to take into consideration the cost per gram of metabolizable Met or Lys delivered per unit of product fed. Other AA may become available in the future.

Of the existing protected Met products, some are true dl-methionine-based products; others are based on methionine analogs (HMB). With true methionine products, companies use encapsulation technologies that are proprietary and unique to each product.

In general, protection consists of being coated with a lipid and other ingredients that resist ruminal degradation while facilitating the release of the methionine in the lower digestive tract. Ideally, the product would be 100 percent ruminal bypass and 100 percent digestible in the lower tract.

Of course, this is not possible and, because the technologies differ, the extent of ruminal protection and release in the lower tract differ among products.

The backbone of the methionine analog-based products is HMB, a methionine precursor. Like with swine and poultry, once HMB is in the blood stream, the cow can make methionine from it. The trick is in having the HMB in the feed reach the blood stream before being used by rumen microbes.

In the U.S., several commercial HMB-based products are available. They range from liquid HMB to dry Ca-salts of HMB to isopropyl alcohols of HMB (HMBi) in a liquid and dry form.

Each product, with its own characteristics, renders from less than 5 percent to up to 40 percent HMB available to the cow for use as a backbone in the production of Met.

Within the last few years, several rumen-protected Lys sources have become commercially available. They too depend on different technologies to confer protection against ruminal degradation. Each has Lys as the backbone. Because each company uses a different technology, the actual Lys concentration, rumen bypass value and intestinal digestibility differ by product.

Nutritionists and dairy producers have better tools than ever to precisely balance diets and better realize each cow’s genetic production and performance potential. The ability to accurately balance amino acids represents a major step forward in dairy nutrition. PD

Luchini is the manager of ruminant product technical services for Adisseo , has a Ph.D. in dairy science from the University of Wisconsin and has received seven U.S. patents.

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Dan Luchini
Manager – Ruminant Product Technical Services
Adisseo

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