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Amino acid digestibility has been a popular topic in my past blogs and trade journals as an important measure of protein quality and that higher digestibility is better. However, what do these values mean and how do differences in digestibility matter in practical situations?
Production animals consume proteins in their diet every day. The protein is typically supplied by grains and oilseeds, but animal ingredients can also be used. Protein consists of long chain amino acids, the building blocks of all proteins; including those in meat, milk, eggs and animal fiber, like wool. Animals must break down the intact proteins from the diet, absorb amino acids across the intestinal wall into circulation (blood) and then use these building blocks to construct protein at the various tissues. If the proper amount and balance of these building blocks are not present, then protein synthesis will not be maximized and animal performance, as measured by body weight gain, will be reduced.
The challenge arises when less than 100% of the amino acids in feed ingredients are available for productive purposes. This is what digestibility attempts to do – estimate the percentage of each amino acid available for protein building. Various animal models have been developed to measure digestibility (for example, see here).
Adding further complexity, digestibility varies based on the ingredient in question, field conditions, composition of other nutrients in the ingredient and diet, animal age, genetics and production level; climate and ingredient processing conditions.
I have blogged in the past about how processing conditions with our equipment results in higher quality soy ingredients (see here and here) and the positive effects of extrusion on available energy levels in ingredients (see here and here). But, what does this mean in terms of diet formulation?
I recently formulated the following broiler diets for one of our prospects:
|Broiler Starter (0-7 d), Cobb||SBM + oil||ExPress ®|
|Corn||44 %||52 %|
|Solvent soybean meal (SBM)||46 %||0 %|
|Veg oil||6 %||0 %|
|ExPress ® soy meal||0 %||44 %|
|Dicalcium phosphate||1.9 %||1.9 %|
|Limestone||1.4 %||1.4 %|
|Salt||0.5 %||0.5 %|
|DL-methionine||0 %||0 %|
|L-lysine||0 %||0 %|
|Mineral/vitamin premix||0.2 %||0.2 %|
|TOTAL||100 %||100 %|
|CP (%)||26.2 %||25.7 %|
|Digestible Lys (%)||1.34 %||1.33 %|
|Digestible Met (%)||0.36 %||0.38 %|
|Digestible M + C (%)||0.72 %||0.78%|
To prove a point, I limited the number of ingredients. Without using any synthetic amino acids (DL-methionine and L-lysine were set to 0) in the complete diet, I achieved higher digestibility levels of methionine (Met) and methionine plus cysteine (M + C) when ExPress ® soy meal was used versus commodity, solvent-extracted soybean meal. The digestible lysine levels were kept equal.
This is because ExPress ® soy meal has higher digestible amino acids than solvent-extracted soybean meal. In this example, less meal was required when it is was processed one way versus the other. Therefore, we can conclude that ingredients with higher-digestible amino acids are higher quality and support equal or greater performance at lower amounts in the diet. Digestibility, therefore, matters tremendously.
Poultry nutritionist face a variety of different challenges when calculating the best formulation for feed. In the February 2015 issue of WATT Poultry USA, Gary Thorton discusses a recent presentation by Dr. Steve Bolden at the Arkansas Nutrition Conference that explores the challenges poultry nutritionists have in formulating broiler feed for yield and economics.
The article and presentation were directed towards nutritionists, however, I believe the ingredients purchasing personnel and the ingredient supplier should understand feed formulation economics as they relate to the specific objective of the integrator/business.
As presented in the article; low, medium, high or extra high density nutrients program can be matched with the profitability of the business as we understand their objectives. Dr. Bolden’s tables within the article reveal three main points to consider when deciding which diet will fit your objective:
1- Low density (lowest cost diet) is the best option if the chicken raised for the live bird market (highest Net $ calculation, last column).
2- High density diet is most economical when growing chicken for the processed birds market. (ExPress® soybean meal works well here).
3- Extra high density diet is the most economical for growing chickens for the boneless breast processed bird market (ExPress® soybean meal works well here).
As concluded above, it is important to understand the end-use of the animal when calculating feed density. This article reminded me of a recent visit I took with a prospective ExPress® soybean meal customer to a broiler facility. As we discussed the high quality and uniqueness of ExPress® soybean meal to the nutritionist and commodity purchasing person, they mentioned they are familiar with the facts and they would not hesitate to use ExPress® soybean meal “when the price is right”.
Their bottom line is how cheap can they buy the ingredients. They are looking at the live bird market economics, but neglecting the fact that their main business is in the further processed meat.
Properly processed ExPress®soybean meal has higher metabolized energy, amino acid digestibility and higher dry matter as compared to solvent extracted soybean meal (click here). ExPress® soybean meal fits well with a formulation program based on medium or high density nutrients.
So, the bottom line is that we along with the integrator’s nutritionist and ingredient purchasing personnel need to understand the marketing objective of the integrator so we can realize the value of a high quality and high density ingredient to match his needs. Furthermore, regardless of the nutrient density formulation, If the integrator’s objective is to produce organic or chemical free chicken, then again, the candidate will be the ExPress® soybean meal based diet.