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Advancia 2017 - Session 1

From scientific reviews to a roundtable addressing questions from the participants and a forum for more questions and answers.


Feedstuff quality: from variation to its appraisal

  • Prof Gonzalo MATEOS (Madrid University, Spain)

Factors of variation of animal digestibility: from in vivo to in vitro models

  • Prof Knud Erik BACH KNUDSEN (Aarhus University, Denmark)

Transforming feedstuffs into digestible nutrients

  • Prof Mike KIDD, Dr Joaquim BRUFAU, Prof Mingan CHOCT
Your questions / Our answers

Q: Is there an optimum age to measure nutritional value in broilers?

This is a very broad question because age-related differences vary depending on different nutrients. For instance, the digestibility of saturated fats differ widely between the starter and finisher period of broilers or pullets and layers. But for practical reasons, you will have to take a compromise; for most nutrients and energy in broilers for instance, a mid point for growth, such as days 21-31 is usually used by most nutrition researchers. In addition, early nutritional values (up to 14 days of age) are critical as limitations in value impact subsequent growth.  Also, depending on target markets, the finishing periods are very important to understand as feed intake is high and any over formulation of nutritional value can be very costly. Some are differentiating the first 10 days from the rest. But considering the small amount of feed given during the first stage, the nutritional values are often not adjusted. However, as Prof Angel mentioned, there are clear differences in P and Ca digestibility for the same ingredient between ages. Feed digestibility values are always a compromise. Standard procedures for AME in chickens exist, and we should use them as stated by Prof Rodehutscord. 

Q: Should we consider different values in starting phase and finishing phase particularly for heavy broilers?

Yes indeed, but always the question of the ROI of having different nutrient values according to age of the animal complexify the formulation work. Thus most people are using 21 days values. Standard procedures are important to follow. Prof Choct insists on the different values of fat between young and older birds. A practical way is to use standard values and deal with compromise, as Dr Clatworthy mentioned.  

Q: Should we consider a global effect of all enzymes as a global solution or should we consider an additive effect between all enzymes?

Enzyme solution depends on the raw material matrix. Using pure xylanase for soybean meal or pectinase for cereals would thus not be appropriate. Theoretical and practical experiments help to consider the whole nutritional matrix. We should not consider an additive effect of the enzyme on its substrates. All the enzymes work on the energy that is not digested, thus on the indigestible fraction and thus cannot be considered as additive but there is more a global answer of the enzymes used. It is clear that considering the global effect of the enzymes on the complete feed might be the most practical approach. Also considering the safety margin might hide the enzyme benefit.

Q: Where are the data suggesting no additive effect of feed additives? Are there raw materials for which this non additive effect is worst? 

Again this is a very broad question when you talk about all feed additives. There is evidence that some additives can work together in a positive manner under certain circumstances. For example, coccidiostats and antibiotics will work together to prevent necrotic enteritis; you may futher improve it if the diet is based on viscous grains, such as wheat and barley, by adding a xylanase and a beta glucanase. But it will quickly encounter the law of diminishing return - once the animal reaches its maximum efficiency, nothing will help it further. As they say, once the cut if full, you cannot fill it more! A number of studies have assessed the additive effects of feed additives. While most showed no additive effects, some showed additional potentials. It will be possible to increase substrate concentration in diets supplemented with combined enzymes. Thus combining enzymes or feed additives may allow increasing the amount of cheaper feed ingredients that are richer in indigestible fractions than most conventional main ingredients. Moreover, substrate availability based on diet (cereal/oilseeds) and enteric health as a function of enzyme efficacy should be studied further.

Q: Given the variation in materials, should we be using table values to formulate?

Most of people are using table values, but often we are using wrong value tables. It is important to always use 1 unique table (not mix values from different tables) and we have to be 80% correct. Many methodologies exist to support the nutritional values, like NIR. It is a pity not to use them. They can provide good corrections. We should be careful to corn, an increase in corn means an increase in zein influencing AA proportions. It is important to base first on tables and adjust with some chemical or rapid measurements  for the batches of ingredients used.

Q: What would be the best advice if a safety margin is applied in the enzyme matrix when various enzymes are used together for energy uplift?*

If you need a safety matrix, you should change your provider!
Combining xylanase and phytase or even more enzymes will not bring an additive effect for sure. Suppliers recommend a matrix that already takes into account the safety margin. According to Dr. Nobelt the response to enzymes is not uniform. Net Energy is the right energy to consider because with ME we can miss some effects. The efficacy of an enzyme or enzyme combination in diet depends on the opportunity given for the enzyme to work with some reduction in nutrients. While safety margin is a way to stay safe, it may also inhibit nutrient efficiency and sustainability and finally increase feed cost. For this reason, customers should rather be more careful on which enzyme(s) they choose to use in their diets. Making sure of animal safety, nutrient efficency, and environmental sustainability depends on collective effort of additive companies to ensure high efficacy of commercially available enzymes and the customers to carefully choose their suppliers.

Q: For SBM, what safety margin or % could you suggest in order to avoid under or over estimation in the analysis and also avoid much changes in the formula?

Better than considering safety margin, it is urgent to develop rapid evaluation methods such as NIRS that would help to take more value of the raw materials.

Q: When comparing corn values across tables, do you think differences are mainly due to analysis methodologies or to differences in corn genetics across regions and overtime? Should we, nutritionists, take more care of agronomy considerations?

Indeed, the corn cultivar, cultural methods and drying processes greatly vary between countries and would affect corn nutritional values. Using large database is thus important to consider, including region, time of year, cultivar. 

Q: How can industry effectively use wet chemistry (primary & variable source of information) vs. NIR (secondary source of information that's based on wet chem)?

NIRS based on regression procedure are much more robust providing information on nutrient content. So, definitively NIRS has to be used more extensively than wet chemistry which is the basis of the NIRS predictions.

Q: When we grind feed particles down to 200 microns, what effect does the DF have on digests flow, nutrient digestion in the SI, and transit to the cecum and LI?

Grinding is a way to reduce the detrimental effect of fiber. Generally, the reduction of feed particle size has been widely believed to enhance the access of digestive enzymes to substrates due to the increased surface area of feed particle. All discussions on particle size have to be considered on digestive tract development, transit time and thus nutrient value. Another key importance of particle size is gizzard development. Too fine particle size reduces gizzard size while too coarse particle size increases the size via funtional hypertropy process and this may be important in part to control the flow of digesta into the SI. 

Q: In pigs, how do NSP enzymes and phytase affect the degradation of NSPs, digests flow and nutrient digestion along the GIT?

NSPs are digested much more efficiently in pigs than in poultry in general, especially in sows and boars. The effect of viscosity in young pigs is as detrimental to nutrient digestion as in broilers albeit the viscosity values appear low and hence often dismissed as not important. The effect of viscosity manifests itself in reducing feed intake in young pigs, which, in turn, affects growth performance. Moreover, the relative low digestibility of starch the two first weeks after weaning might be worthwhile to consider. For growing-finishing pigs, viscosity is generally not considered an issue for digestion and absorption except that it may influence endogenous secretions and thereby the cost of digestion. 

Q:  What are the most valuable expression of dietary fiber in the feed?

The term that best captures the fibre content of feed is total dietary fibre, which can be measured using a gravimetric method or a GC technique. Both methods can be found in the AOAC Methods.

Prof Choct wrote an article on fibre and the details can be found at:

Total dietary fibre can be measured by the enzymatic-gravimetric AOAC assays or as NSP and lignin using enzymatic-chemical-gravimetric principles. Insoluble fiber components should be considered for a good correlation. Crude fiber depends on the extraction process, so that means nothing (example for Soyabean: CF is very low but real fibre components can be much more variable), CF is not precise enough. Considering NSP is not far from the real content of fiber. Resistant starch is another important component to consider and may depend on processing conditions of the feedstuffs.

Q: Can the maturity of the grain affect its digestibility? If so, how we could measure this parameter?

Some results suggest an effect of storage on raw material nutritional values. It could be measured by evolution on nutrient content; that's why it is important to adjust table values with direct measurement on the batches used .

Q:  How much important to calculate the AME could be to analyze amylose and amylopectin in the corn?

The amylose and amylopectin ratio is a key factor for corn seed selection. This selection resulted in waxy corn (100% amylopectin). From our knowledge, they mainly resulted in differenciation for ruminant nutrition. For monogastric animals, the AME is not affected by the amount of amylose and amylopectin and there are no data that indicate that the amylose/amylopectin ratio play any significant role on the digestibility of starch.

Q:  How to take into account sugar composition of raw materials in formulation tables?

We need to have several new items in our databases, including total, soluble, insoluble and total NSP as well as the free sugars, which represent CHO ranging in one to 12 monosaccharides. Sugars such as arabinose, xylose, mannose and others would help to better define the amount of antinutritional factors present in the raw material and the amount of substrate for feed enzyme. By this way, specific carbohydrase supplemented in diets would be based on the level of indigestible fractions. This would also be of additional benefit to broiler in the early post-hatch period as having a considerablely highly ready-to-absorb sugar would put less pressure on the pancreatic secretion at this age.

Q:  Do feed mills have a decision process to chose and buy the right corn varieties, best suitable for animal nutrition?

Moisture, Crude Protein and contaminant content are the three main criteria to be considered. But feedmillers are also concerned by delivery date, delivery method, and price which is decided between the corn buyer and nutritionist.

Q:  What is the impact of enzymes addition on the prebiotic potential of raw materials?

No doubt that some enzymes may create carbohydrates with prebiotic properties. As host, birds symbiotically rely on good microbiota. Hence, the activity of supplemented enzyme to increase oligosaccharide concentration in the GIT may help to feed the good bacteria colony.

Q: What is the impact of enzyme supplementation on mycotoxins?

No direct effect as if talking about NSPase, phytase… do not breakdown the mycotoxins. However, all additives reinforcing the immune response of the intestine or improving its antioxidant status might help to resist to the negative effects of mycotoxins.

Q: Commercially, we make feed diets with ingredients of unknown quality/ nutrient comp. How do we overcome this & avoid bacterial imbalance & performance drag?

Considering rapid and complementary measurements on feedstuffs is critical.

Q: How could we put figures on health for objective evaluation?

Taking into consideration the microbiota, and all additives or factors influencing the intestinal microbiota will affect the response to enzymes or even will affect the nutritional value of feedstuffs and should be better considered. Intestinal inflammation and gut integrity are key also for the nutritional value appraisal. Formulating on NE basis might be the only option.