A birds eye on Arginine
Arginine (Arg) is an essential amino acid for poultry since birds are not able to synthesize this amino acid themselves. Arg is involved in numerous processes in the body, including protein synthesis. Therefore a deficiency in arginine will lead to reduced growth and feed conversion. The question of course is when does a deficiency occur, and can we expect other benefits of Arg when levels are increased further?
Arginine requirements for technical results
In literature, a wide range of Arg to Lys recommendations can be found. In general, a ratio of SID Arg/SID Lys can be found between 100 and 125%. This wide range is partly caused by gender (males respond to a higher ratio compared to females), parameter (growth or feed conversion, whereas the ratio for best FCR is higher than for body weight), and age of birds (response to different arginine levels in feeds by older birds is more variable). In 2019 Ospina-Rojas et al. published a solid review article based on a meta-analysis of 94 treatments coming from 8 peer reviewed papers. In Figure 1 the results of the relation between arginine intake versus realized growth of this meta-analysis are shown.
Recalculating these data, assuming a SID lys level of 12,8gr/kg in the start (0-21 days) and 10,7gr/kg in the grower/finisher (22-42 days) and by using different models, the ideal ration SID Arginine/Lysin could be determined. This resulted in an ideal ratio of Arg/Lys at 114% and 115% respectively in the starter and grower. These levels are considerably higher than mentioned in many literature sources so we conducted our own research. We also concluded that higher ratios, compared to current standards, do have a positive effect on the technical results. However, the ratio SID Arg/Lys can be a very expensive bound in your feed formulation so the economical optimum can be considerably lower.
Other benefits of Arginine
Arginine is not only a building block for protein synthesis. It also functions as a substrate for the biosynthesis of many molecules, including nitric oxide, creatine, ornithine, glutamate, proline, and agmatine. Moreover, Arg also seems to reduce abdominal fat, having a positive effect on carcass yields. Arg is also associated with a reduction in oxidative stress. During a broiler cycle, birds can be exposed to various stressors, like stocking density, transport- and temperature stress. This stress can lead to oxidative damage which negatively affects meat quality and performance results.Especially the formation of Nitric oxide (NO), plays an important role in various processes.
It acts as a vasodilator. So during heat stress, more blood can be directed to the peripheral tissues dissipating more heat from the body. Also, there are indications that the enhanced blood flow to the muscles/skin improves the healing of wounds (scratches). Due to improved collagen synthesis and removal of harmful catabolites, partly by better functioning of the macrophages (Alexander and Supp 2014). Also when birds have experienced cold stress, potentially leading to pulmonary hypertension syndrome and sometimes ascites, Arginine can have a positive effect (Olkowski et al. 1999). The vasodilation function of NO is reducing blood pressure leading to less tension in the heart and lungs.
Conclusions and recommendations
Based on the results and literature it is clear that it is worthwhile to take SID Arg/Lys ratio into account when technical results need to be improved. Next to that, it is also a very interesting amino acid when it comes to improving the general health of the birds or increasing their capability to deal with all kinds of stressors.
Depending on the prices of raw materials and synthetic Arginine, next to the challenges in the field, it is recommended to keep this ratio in mind, and possibly increase it while optimizing broiler diets.
For more information or to revise your situation, please contact Koudijs Technical support.