High Available Lysine Content in Feed Means Higher Quality Protein for Pigs

Lysine is often the first-limiting amino acid in pig diets, particularly those based on cereal grains, and a high available content is crucial for protein quality. A feed's protein quality is not just about the total amount of crude protein, but the balance and bioavailability of its constituent amino acids, with lysine playing the most prominent role.

Quick Summary

A diet high in available lysine directly improves the quality of protein for pigs because lysine is the first limiting amino acid, governing how efficiently other amino acids are utilized for muscle growth and other vital functions. Without sufficient lysine, excess protein is wasted, leading to poor growth performance and increased nitrogen excretion. This principle, known as the 'ideal protein' concept, is foundational to modern, cost-effective, and environmentally sustainable swine nutrition.

Key Points

• First Limiting Amino Acid: Lysine is typically the first limiting amino acid in pig diets, governing the extent of protein synthesis.

• Available vs. Total Lysine: Available lysine, the usable portion, is more important for protein quality than total lysine.

• Maximizing Protein Synthesis: Adequate available lysine ensures efficient use of other essential amino acids for growth.

• Improving Feed Efficiency: High available lysine leads to better feed conversion and carcass quality.

• Reducing Environmental Impact: Balancing amino acids with sufficient available lysine minimizes nitrogen excretion.

• The Ideal Protein Concept: This approach balances essential amino acids relative to lysine for optimal performance.

Understanding the Role of Lysine in Protein Synthesis

Protein synthesis is a complex biological process that requires the presence of all essential amino acids (AAs) in adequate amounts. Pigs require ten essential AAs from their diet as they cannot synthesize them internally. Lysine is particularly important as it is commonly the first essential AA to be deficient in typical grain-based feeds.

Protein synthesis can only proceed based on the availability of the most limited essential amino acid. If lysine is deficient, the pig's ability to synthesize proteins is restricted, even if other AAs are abundant. This surplus of other essential amino acids is then metabolized and excreted as nitrogen waste, which is inefficient and environmentally undesirable.

The Importance of Available vs. Total Lysine

It is crucial to differentiate between total lysine and available or standardized ileal digestible (SID) lysine. Total lysine is the measured amount in the feed, while available lysine is the portion that the pig can absorb and use. Processing, such as heat, can reduce lysine availability. Therefore, high available lysine is more critical for protein quality than high total lysine alone.

Key reasons why high available lysine ensures higher quality protein:

• Governs Protein Synthesis: Protein deposition is closely linked to the supply of the most limiting amino acid, usually lysine.
• Maximizes Feed Efficiency: Sufficient available lysine allows other essential AAs to be fully utilized, optimizing protein accretion and feed-to-gain ratios.
• Reduces Waste: Proper amino acid balance minimizes the excretion of excess nitrogen.
• Promotes Lean Growth: Higher available lysine ratios support increased lean muscle and reduced backfat.

The Ideal Protein Concept

The "Ideal Protein" concept in swine nutrition aims to provide the optimal balance of essential amino acids relative to lysine to maximize growth and protein synthesis without excess. This approach allows nutritionists to precisely meet the pig's needs at each growth stage, potentially lowering total crude protein levels through the use of synthetic amino acids.

Comparison of High vs. Low Available Lysine Diets

Feature	High Available Lysine Diet	Low Available Lysine Diet
Protein Quality	High; balanced AA profile	Low; imbalanced AA profile
Muscle Growth	Maximize lean muscle	Poor muscle development
Feed Conversion	Efficient growth	Inefficient growth
Carcass Quality	Higher lean meat, less backfat	Increased fat
Nitrogen Excretion	Lower waste	Higher waste
Cost-Effectiveness	Potentially lower feed costs	Higher feed costs per gain
Health & Immunity	Supports robust immunity	Can impair immunity

Conclusion

Protein quality for pigs is significantly influenced by the available lysine content in feed, as lysine is typically the first-limiting amino acid. A high level of available lysine ensures efficient utilization of other amino acids for protein synthesis, leading to improved growth, feed efficiency, and carcass quality. Implementing the 'ideal protein' concept, which prioritizes available lysine, allows for economically sound and environmentally conscious swine diets. Focusing on available lysine helps producers optimize herd potential and minimize protein waste.

For further reading on lysine in swine nutrition, consult resources like the article "Lysine nutrition in swine and the related monogastric animals".

Frequently Asked Questions

What does 'first-limiting amino acid' mean for pigs?

It refers to the essential amino acid in shortest supply relative to the pig's needs. Lysine is commonly first-limiting in cereal-based diets, restricting protein synthesis and growth.

What is the difference between total lysine and available lysine?

Total lysine is the chemical amount in feed, while available lysine is what the pig can digest and absorb. Availability can be reduced by processing.

Why can't pigs simply use other amino acids if lysine is low?

All essential amino acids are needed simultaneously for protein synthesis. A lysine deficiency prevents full utilization of other AAs, leading to their breakdown and excretion.

How does higher available lysine improve pig growth?

Sufficient available lysine allows efficient synthesis of lean muscle protein, resulting in faster growth, improved feed conversion, and better carcass quality.

What is the 'ideal protein' concept in pig nutrition?

The ideal protein concept aims to provide the optimal balance of essential amino acids relative to lysine for peak performance, often using lysine as a reference.

Is it better to use synthetic lysine or add more high-protein ingredients?

Using synthetic lysine helps meet specific needs without adding excess protein. This can be more cost-effective and reduces nitrogen excretion compared to relying solely on high-protein ingredients.

Does a high available lysine content affect pig health?

Yes, adequate lysine supports overall health and immune function. Deficiency can impair immunity, while appropriate levels aid in synthesizing immune proteins.