Realising the Full Potential of Broiler
Performance with Versatile Functions of L-Arginine
By Estella Koo, Technical Manager for L-Arginine, CJ CheilJedang BIO
L-Arginine is an essential amino acid for broilers because there is no de novo synthesis of L-Arginine in broilers. Arginine is involved in several functions in broilers such as fat reduction, heat/cold stress alleviation, bone development, reproduction improvement, etc.
When the 1998 Nobel Prize winners in Physiology or Medicine were announced, it emerged that three scientists had shared the prize for their discoveries of ‘nitric oxide as a signaling molecule in the cardiovascular system’. Their research showed that neither hormones nor other large molecules, but the tiny nitric oxide molecule is a key to vascular relaxation. Additionally, they discovered that nitric oxide is responsible for the relaxation of smooth muscles in blood vessels. Many studies are still being done with nitric oxide. There are more than 150 thousand studies thus far (PubMed, 2018). Many of these can be applied in our daily lives. For example, Sildenafil (Viagra), which basically widens the blood vessels, is not used in the originally intended area – heart disease – but now it is used in the very different area.
Figure 1. Nitric oxide and vascular relaxation Figure 2. Nitrogen excretion by animals
reptiles excrete uric acid, mammals excrete urea, and fish excrete ammonia (Figure 2). Mammals can synthesize arginine via the urea cycle; however, birds lack two key enzymes (carbamoyl-phosphate synthetase, and ornithine carbamoyl transferase) in the process, so de novo synthesis cannot occur. Arginine requirement has increased with genetic improvement.
This is because modern broilers have been selected to grow faster with a higher rate of protein deposition. Therefore, requirement levels of amino acids including lysine are higher. Furthermore, antagonism between lysine and arginine has also increased the arginine requirement. Table 1 shows the general commercial broiler breed ROSS308’s amino acids requirements. The L-Arginine requirement increased more than other amino acids in the 2014 guide as compared to the 2007 guide. It suggests that functions of arginine have become more recognized.
Table 1. ROSS308 (Aviagen) amino acids requirement
Nitric oxide is synthesized from arginine after conversion to
citrulline. Arginine is one of 10 essential amino acids. It is also used for synthesis of polyamine, creatine, glutamate, etc. Professor Guoyao Wu, an expert in amino acids for animals, has stated that “Arginine is one of the most versatile amino acids in animal cells (Guoyao Wu, 1998).”
L-Arginine: Essential Amino Acid for Broilers L-Arginine is an essential amino acid for broilers as they have no de novo L-Arginine synthesis pathway. The urea cycle is why L-Arginine is a semi-essential amino acid for mammals such as swine or humans, but it is an essential amino acid for broilers. The urea cycle is associated with arginine biosynthesis. Animals excrete nitrogenous wastes, and animal can be divided into 3 groups based on major nitrogenous compounds. Birds and
PAGE 28 SEPTEMBER/OCTOBER 2018 FEED COMPOUNDER
Figure 3 shows the study done by IRTA (2016). It demonstrated
that modern broilers need at least ARG:LYS=115% for maximum live performance. This is higher than the present standards (106%).
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