Dr. Michelina Crosbie: Amino Acid Bioavailability
Audio Brief
Show transcript
This episode explores Dr. Michelina Crosbie's PhD research on amino acid bioavailability in dogs, highlighting its critical role in pet nutrition.
Here are four key insights from this discussion. First, an ingredient's true nutritional value for pets is determined by amino acid bioavailability, not just its crude content. Second, the Indicator Amino Acid Oxidation, or IAAO, technique provides a precise, non-invasive method to assess how dogs utilize dietary amino acids. Third, ingredient source and processing significantly impact nutrient utility, with methionine in chicken meal showing better bioavailability than in peas within extruded diets. Finally, novel research methods like IAAO are essential for optimizing pet food formulations, especially when incorporating diverse protein sources.
Bioavailability measures the proportion of an absorbed nutrient truly available for metabolic processes, such as protein synthesis. This differs from simple digestibility, which only accounts for nutrient absorption from the gut. Understanding bioavailability ensures diets provide usable nutrients.
The IAAO technique assesses specific amino acid bioavailability by observing the oxidation of other amino acids when the test amino acid is limiting. By measuring labeled carbon dioxide in exhaled breath, researchers quantify the body's utilization of an amino acid. This method is crucial for accurate nutritional evaluation.
Methionine, often a limiting amino acid in plant-based ingredients like peas, is vital for protein and taurine synthesis. Research demonstrated superior methionine bioavailability from chicken meal compared to peas when both were in extruded diets. This highlights the importance of ingredient selection and processing methods on nutrient utilization in pet food.
As the pet food industry increasingly uses varied traditional and alternative protein sources, advanced techniques like IAAO become indispensable. This type of precise research allows for the development of nutritionally complete and optimized diets, moving beyond mere ingredient analysis.
This research offers critical insights for refining pet food formulations to better meet canine nutritional needs.
Episode Overview
- Host Dr. Jan Suchodolski welcomes Dr. Michelina Crosbie to discuss her recent PhD research on amino acid bioavailability in dogs.
- The episode focuses on the difference between nutrient digestibility and bioavailability, emphasizing that bioavailability is a more accurate measure of what the body can actually use.
- Dr. Crosbie explains the Indicator Amino Acid Oxidation (IAAO) technique, a non-invasive method used to determine the bioavailability of specific amino acids like methionine.
- The discussion covers challenges and findings from applying this technique to extruded pet food ingredients, such as peas and chicken meal, in the context of canine nutrition.
Key Concepts
- Bioavailability vs. Digestibility: Digestibility measures the proportion of a nutrient absorbed from the gut. Bioavailability goes a step further, quantifying the proportion of the absorbed nutrient that is actually available for the body's metabolic processes, such as protein synthesis.
- Indicator Amino Acid Oxidation (IAAO) Technique: This is a method to measure the bioavailability of a specific amino acid. It relies on the principle that when one essential amino acid (the test amino acid) is limited, other amino acids in excess (the indicator amino acids) are oxidized. By measuring the oxidation of a labeled indicator amino acid (e.g., in exhaled CO2), researchers can determine how available the test amino acid is.
- Methionine's Importance: Methionine is often the first limiting amino acid in plant-based ingredients like peas. It is crucial for protein synthesis, taurine synthesis, and other vital metabolic functions. Its bioavailability is a key factor in formulating nutritionally complete diets, especially those with high plant-protein content.
- Research Challenges: The IAAO technique is expensive and requires specialized equipment and highly trained personnel. Adapting the method from pig nutrition (where mash diets are common) to dog nutrition (where extruded kibble is standard) presented challenges, particularly in creating a suitable reference diet.
Quotes
- At 00:00 - "it was a logical flow because bioavailability takes kind of digestibility and...it's able to actually account for not only just the portion of the amino acid that just disappears from the end of the small intestine...it actually can quantify the portion of that amino acid that went in in the first place...and what portion of that amino acid is actually able to be used for other metabolic processes." - Dr. Crosbie explains why bioavailability is a more comprehensive measure than simple digestibility.
- At 13:31 - "Protein synthesis is basically inversely proportional to oxidation. So when one amino acid is limiting, then all other amino acids even above that level are going to just be oxidized." - Dr. Crosbie describes the fundamental principle behind the Indicator Amino Acid Oxidation (IAAO) technique used in her research.
- At 23:23 - "So that study was really interesting in that we found actually bioavailability didn't change over time...what we got after two days diet adaptation, which is standard for IAAO, was not different from what we got when we did it after seven days." - Dr. Crosbie shares a key finding that the adaptation period for this specific test in dogs might be shorter than traditionally thought.
Takeaways
- Simply knowing an ingredient's amino acid content is not enough; its bioavailability determines its true nutritional value for the pet.
- The Indicator Amino acid Oxidation (IAAO) technique offers a precise, non-invasive way to evaluate how effectively dogs can utilize amino acids from different protein sources in their food.
- Processing matters: The bioavailability of methionine in chicken meal was found to be better than in peas within the same extruded diet batch, highlighting that ingredient source and processing can significantly impact nutrient utility.
- Novel research methods like IAAO are crucial for refining pet food formulations, especially as the industry explores a wider variety of traditional and alternative protein ingredients.
