WHAT IS ESSENTIAL AND WHAT IS NOT
The understanding of essential amino acid (EAA) requirements has enabled the reduction of dietary protein content without compromising animal performance. However, the role of non-essential amino acids (NEAA) and dietary nitrogen in low protein diets remains crucial. A deeper insight into how dietary protein and NEAA influence amino acid utilization and growth is pivotal for enhancing animal performance while minimizing costs and environmental impact in animal agriculture.
The retention of dietary nitrogen in pigs ranges from 30% to 60% of intake, with inefficiency arising from excess or unbalanced amino acid intake leading to catabolism. This catabolism not only incurs an energetic cost but also diminishes performance, elevating nitrogen excretion. Utilizing synthetic AA and the 'ideal protein concept' permits precise ration formulation while decreasing crude protein content.
But this new strategy of low protein creates a new risk on pigs' ability to meet NEAA demands. Reduced growth performance in such diets suggests NEAA's potential significance, with studies indicating a minimum NEAA (or total dietary nitrogen) requirement to maximize growth and nitrogen retention.
Catabolism of EAA for endogenous NEAA production may contribute to reduced performance in low protein diets. Current EAA requirement estimates might not reflect the needs of NEAA in low protein diet. In addition to the monitoring EAA, studies suggest to look as well at the significance of an optimal EAA to total nitrogen ratio (EAA:TN).
Advantages of Reducing Dietary Protein Content:
Reducing dietary protein content yields numerous benefits. Each 1% reduction results in a 3% reduction in protein ingredient utilization, subsequently lowering feed costs. Moreover, ammonia emissions decrease by 8-10% for every reduction in dietary protein, improving the environment and overall well-being. These reductions also combat issues like post-weaning diarrhea. However, maintaining pig performance is essential for sustained benefits.
Redefining Non-Essentials:
Previously, the focus primarily rested on the twelve amino acids classified as essential, as animals cannot synthesize them on their own. The rest, known as non-essential, were often relegated to the sidelines. However, groundbreaking studies have unveiled a new truth – animals require both essential and non-essential amino acids for optimal growth and performance as the synthesis of non-essential may not be sufficient, especially on highly productive animals. Neglecting NEAAs can result in suboptimal growth and hindered production.
Swine: Enhancing Structural Integrity
Let's consider the swine industry, where growth and efficiency are the ultimate goals.
While essential amino acids lay the foundation, non-essential ones like proline and glycine come into play for collagen formation, supporting connective tissues, and improving meat quality. Examples in support of this notion are many, including arginine for gestating and lactating swine; glutamine for suckling piglets; arginine, glutamate, glutamine, glycine, and proline for post-weanling nursery pigs; and glycine for growing-finishing pigs. Thus, we must move beyond the long-standing “ideal protein” concept, which ignored all the NEAAs, in animal nutrition.
Ignoring these NEAAs could lead to weaker structures, reduced carcass value, and economic losses – underscoring their importance.
Fish: The Aquaculture Equation
In the realm of aquaculture, non-essential amino acids emerge as key players. Take arginine as an example – although non-essential, it's crucial for ammonia detoxification, maintaining water quality in aquaculture systems. By accounting for NEAAs, nutritionists bolster fish health, reduce stress, and contribute to sustainable aquaculture practices that harmonize with the environment.
Poultry: Beyond Basics
Poultry production thrives on precision, and NEAAs are integral to this success. Glycine and glutamine, while non-essential, serve as nitrogen sinks, essential for uric acid production. When fed conventional diets, poultry do not synthesize sufficient glycine, glutamate, or glutamine. Second, unlike mammals, the skeletal muscle (e.g., breast muscle) of poultry has a limited ability to transport glucose due to the absence of glucose transporter-4 and instead uses glutamine as a major energy source for protein synthesis, growth, and tissue integrity. Third, poultry has a limited arginase activity for proline synthesis and thus their diets must contain sufficient proline to meet metabolic needs. Recent studies confirmed that, in chickens, proline is a major substrate for the renal synthesis of polyamines (putrescine, spermidine, and spermine) for other tissues. These unique substances are essential for DNA and protein synthesis and, therefore, the growth, development, and reproduction of poultry.
Sourcing the Essentials: Nutrient Diversity
Diverse feedstuffs remain the primary source of amino acids for animals. Unfortunately, plant proteins often lack adequate amounts of NEAAs like glycine and proline, along with essential amino acids such as tryptophan, lysine, methionine, and threonine. Moreover, taurine and creatine – essential for various bodily functions – are absent in plant-based feeds. This emphasizes the significance of animal-sourced by-products that offer a comprehensive amino acid profile.
It is today quite complex to track all the amino-acids. A focus is already done on formulating with 3, 5 and sometimes 8 essential amino-acids to guarantee the ideal amino-acids profile. It would be too complex to do similar exercise for all the 20 amino-acids.
One recommended strategy is to use dietary protease to maximize the release of all the non-essentials present in the diets. It does not enable us to monitor them individually, but it gives an assurance to the nutritionists that it will get the best out of the ingredients he has in hand. Studies show indeed that dietary protease help to regain production performance both on Poultry, Swine, Fish and even Shrimp.