July 19, 2019

Towards Resolving Unsettled Issues in Poultry Nutrition | PSA Informal Nutrition Symposium Notes

Tags: Poultry | Broiler | Enzyme | Conference

Towards Resolving Unsettled Issues in Poultry Nutrition | PSA Informal Nutrition Symposium Notes

Happy Friday everyone! I wrote this post yesterday on my flight back home from Montreal, recapping what I've learned from PSA this year. Hope you enjoy it! :)

Hello from up in the air!

I'm on my way home from Montreal, Canada, a 6-hour flight is perfect for a 2h nap and some blogging. :)

This past week, I attended the Poultry Science Association (PSA) meeting in Montreal. This is my 9th year for PSA since I was a grad student, and it has become something I look forward to every summer. Like always, this year’s PSA is filled with many wonderful friends, many great talks, many good interactions and discussions…it is like a family reunion that brings the poultry community together. Kudos to the organizing committees and volunteers who have worked hard to put this together!

This year, the symposiums were especially well organized with high quality presentations. Here are some selected notes from the Informal Nutrition Symposium I had in my notebook --- while recapping what I've learned, I thought I would share it with you all. I know some may have not been able to attend this year, so hopefully you will find it helpful.  :)

1)  Dr. Carl Parsons (University of Illinois) --- Digestible Amino Acids

(Dr. Parsons is my M.S. advisor. As amazing as he is, he usually does not come out and give presentations that much, so of course we had to sit in the front row to support! And of course, Dr. Parsons never disappoints with his unique sense of humor haha😀)

Dr. Parsons's presentation reviewed multiple issues that that our community have faced or are currently facing in terms of determining/utilizing digestible amino acid values.

  • Issue 1: Do we need to formulate on digestible or total amino acid levels?
This is a well-addressed question and we have a general agreement that we need to go for digestible amino acids, as total amino acids often underestimate the value of ingredients.
  • Issue 2: What assay to use to determine digestible amino acids?
There are multiple assays available: Growth assay (which measures the slope ratio when feeding a standard amino acid vs. the feedstuff, but this method is time consuming and can only analyze one amino acid per assay); the Precision-fed rooster assay (which is highly repeatable, although it has received some critics over the years, it is a fast and pretty accurate assay); and Digestibility or Balance assay (which is widely used today).
  • Issue 3: Are the rooster values and chick values interchangeable?
There are some variance, but no consistent differences for amino acids have been noticed.
  • Issue 4: Apparent vs. Standard digestibility?
Standardized digestibility wins (apparent values underestimate digestibility, especially with low-protein ingredients)
  • Issue 5: what type of basal endogenous correction should you use?
Current methods include fasted birds, nitrogen-free diet, highly digestible protein diet, and regression method. The first 2 are probably the most commonly used methods.
  • Issue 6: Should you determine basal value in each assay or use one for all assays?
Dr. Parsons suggests one for all assays (because there is not much variation)
  • Issue 7: What marker to use?
Acid insoluble ash (the most accurate one, but usually there is not enough digesta sample to analyze); chromium(iii) oxide (easy to spot whether it is added at the right level), titanium dioxide (the most often used method)
  • Issue 8: Should you use the analyzed marker concentration in each individual diet or use on average value for all diets?
Dr. Parsons suggests one value for all (because the difference might be just due to lab analytical error)
  • Issue 9: Which assay should you use for when evaluating enzymes?
Use standardized ileal digestibility broiler assay with a diet that is as practical as possible. Keep the number of treatments low and the number of replicates high.
  • Issue 10: With the use of enzymes, can the digestible amino acids concentration exceeds the total amino acid level?
If this happens, it is a damn good enzyme! 😹
  • Issue 11: Effect of bird age on amino acid digestibility?
As age increases, amino acid digestibility increases.
  • Issue 12: What values should you use for digestible amino acid requirement?
Track levels of total amino acid formulas, and refer to university research trials. (right now we need more data on arginine and isoleucine requirement, as they are likely the next ones coming to market).
Standardized vs. Apparent digestibility (Cited from Lemme et al., 2014)
Endogenous loss of amino acids (Cited from Lemme et al., 2004)

2) Dr. Martin Zuidhof (University of Alberta) --- Matching Nutrient Digestibility Data with Practical Feeding Strategies

(This is a really interesting talk that gives us a glimpse of the future of poultry production that combines technology and nutrition to achieve precision nutrition. It reminds me of the last Research Digest that I wrote on individualized nutrient requirement - if you haven't read it, here is the link!)

For nutritionists, our ultimate goal is to match nutrient supply to nutrient requirement, yet nutrient requirement is very dynamic and changes depending on the specific genome, environment, and stage of life.

In the swine world, it was found that daily individual tailoring of pig diets without compromising performance can reduce N excretion by 30% and decrease feed cost by 10-15% (Andretta et al., 2016).

For poultry, Dr. Zuidhof has figured out a “Precision Feeding Station” for broiler breeders --- when a bird walks in, it is weighed and compared to the standard BW, if the bird is heavier than standard, no access to feed is provided; if it is under weight, then access to feed is allowed. If the bird tries to stay longer to eat, it even gets pushed out! 😂

(Cited from Zuidhof et al., 2017)

Another type of feeding station Dr. Zuidhof mentioned can also blends a diet that fits the specific bird entering the station from a couple of stock feeds, and therefore is able to provide the exact formulation/amount for the individual bird that enters the station.

These feeding stations work pretty well to improve flock uniformity, and reduce N excretion and feed cost for broiler breeders. However, its utilization might be limited in broiler production, as each station can only accommodate 50-100 birds (so one will need at least 300 stations for a 30,000-bird house). Another challenge would be to quantify responses to nutrient levels for bird-to-bird variation and associate that variation with identifiable traits (such as breed, sex, age, BW, growth rate, environment, health status, etc.)

We certainly hope that in a near future, we will be able to see individual precision feeding system coming together with a combined effort of new technology (e.g. real-time sensors on different traits), data science (e.g. simulation models), and nutrition!

(Here is a video about the Precision Feeding Station from Dr. Zuidhof)

3)  Dr. Mike Bedford (AB Vista) --- Matrix Values for Exogenous Enzymes

In this presentation, Dr. Bedford discussed the importance of understanding enzyme matrix values  ---  what is "matrix" exactly? My understanding is that different enzymes release different nutrients,  and the level is dependent on many factors (enzyme type, dose, ingredient, nutrient density, animal, etc.). So understanding how much exactly each nutrient is spared by a certain dose of a certain enzyme under a given scenario is important, because it can help nutritionists formulate more accurately --- not too low to lead to a likelihood a performance failure, but not too high to lead to unnecessary feed cost and waste.

Therefore, the goal of the whole "Maximum Matrix Nutrition" introduced by AB Vista is that "...diets can be formulated with higher nutrient credits delivering considerable feed cost savings and minimizing waste".

At this point, there are different methods for derivation of a matrix --- primarily digestibility assays and comparative assays. In the case of digestibility assays, the site of sampling makes a different: an ileal collection would be more relevant for phytase and protease, while an excreta collection would be more relevant for NSPase. Yet digestibility alone is not sufficient to support a matrix value. Also, when evaluating performance, effect on feed intake should not be neglected.

I didn't write down the detailed results/values from various research projects that Dr. Bedford shared, but the take home message is that a lot more research and supporting performance data relevant to the end users will be essential going forward.

More information on Maximum Matrix Nutrition can be found here: Link

(Recreated based on Bedford, 2019)

4)  Dr. Aaron Cowieson (DSM) – Applying Enzyme Matrix Values in The Real World

Dr. Cowieson's presentation goes hand in hand with the previous one from Dr. Bedford. I didn't write down much specifics, but Dr. Cowieson has shared multiple recent research outcomes that help better our understanding of the value of exogenous enzymes. Although exogenous enzymes that we use today carry "a degree of ambiguity into feed formulation with respect to overlapping matrices, variability and the breadth of effect across multiple nutrient domains", with the combined effort of the poultry industry and academia, we have gathered more and more information as to how enzymes work in the real world.

Currently, carbohydrase tends to be assigned an AME value of 50 – 100 kcal/kg (sometimes also an1-3% value on amino acid release). Phytase tends to be assigned a P and Ca value of 0.12-0.18%. In general, enzyme matrix increases inclusion of limestone and cereal, while reduces soybean meal, P and added fat. In practice, value of exogenous enzymes depends on the ratios of the cost between cereal and protein meals.

📍 Here is an interesting related read from Dr. Cowieson on protease:
Toward optimal value creation through the application of exogenous mono-component protease in the diets of non-ruminants

📍 More information on common questions regarding feed enzymes can be found here:
Enzyme FAQs

Questions from the Audience

This year, the symposium very creatively adapted the use of an app for the audience to ask questions real-time, so we had a lot of good questions and interactions. Here are some interesting ones:

- What markers will you be using for bird health in your "precision-feeding" system?
- If you feed all individuals to their genetic potentials, would you exacerbate variation on flock uniformity?
- How much differences in amino acid digestibility in different breed? i.e. different breeds of broilers, quails, laying hens
- How much transparency should feed additive suppliers provide to end users when it comes to the matrices, how they were derived and how variable they are?
- Should we discount enzyme matrices based on their variability?
- With the extra-caloric effect of fat on CHO, ME, how would we formulate with that relationship when we typically set our ME min/max?
- For carbohydrases, do you foresee a 'rapid' AME/nutritional matrix test for incoming/received ingredients?
- What about the interaction of exogenous enzymes and the host microbiome? .....and many more.

Something for us to think about over the weekend. :)


Andretta, I., Pomar, C., Rivest, J., Pomar, J. and Radünz, J., 2016. Precision feeding can significantly reduce lysine intake and nitrogen excretion without compromising the performance of growing pigs. animal, 10(7), pp.1137-1147.

Lemme, A., Ravindran, V. and Bryden, W.L., 2004. Ileal digestibility of amino acids in feed ingredients for broilers. World's Poultry Science Journal, 60(4), pp.423-438.

Zuidhof, M.J., Fedorak, M.V., Ouellette, C.A. and Wenger, I.I., 2017. Precision feeding: Innovative management of broiler breeder feed intake and flock uniformity. Poultry science, 96(7), pp.2254-2263.

Wow, this is a long post today! Please feel free to leave any comments or suggestions belowI would love to hear any feedback or just a hello from you!

Have a wonderful weekend!Until Next Time 😊

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