ARTICLE FEED & ADDITIVE MAGAZINE August 2025 83 creatine, glutamine, glutamate, and ornithine (Khajali and Wideman, 2010). Arginine modulates the immune response directly through the production of nitric oxide and ornithine (Le Floc’h et al., 2004) and promotes the proliferation of lymphocytes in Peyer’s patches and stimulates the secretion of anabolic hormones such as growth hormone and insulin-like growth factor-1 which promote protein synthesis and wound healing. Nitric oxide acts as a cytotoxic mediator of immune-activated cells and regulator of the immune system (Hibbs et al., 1988). Arginine also serves as a precursor for the synthesis of polyamines, which are important for cell division and gene expression (Le Floc’h et al., 2004). In a recent evaluation of the optimal ratio of arginine to lysine in Ross 708 broiler males, Corzo et al., (2021) observed that the ratio needed to optimize body weight gain, feed conversion ratio, and breast meat weight was 129%, 116%, and 112% respectively (Figure 1). Corzo et al. (2021) also reported linear increases in thigh weight and yield with increasing arginine ratio during the finisher phase, concluding higher dArg/dLys needs as the bird ages are likely due to the considerably high maintenance value of arginine in broilers. Performance enhancement with increasing arginine to lysine ratios were also reported by Oliveira et al., (2022) with a linear increase in body weight with arginine ratios ranging from 96% up to 124% of dLys with similar linear reduction in feed conversion ratio in Cobb 500 broilers. Anderson et al., (2023) also reported linear effects on body weight with increasing arginine ratios in Cobb 500 broilers. Interestingly, Oliveira et al., (2022) evaluated an arginine dose response on skin thickness and strength in addition to the increasing arginine impact on muscle creatine level. The authors reported a linear increase in skin thickness (sampled from the left and right pelvic back region) and skin strength at 44 days of age as arginine ratio was increased from 94% to 124% of dLys. The highest evaluated arginine level of 124% of dLys resulted in a skin thickness of 1.211 mm and a strength of 10.171 mm as compared to 0.898 mm thickness and 5.154 mm strength from broilers fed a diet containing an Arg ratio of 106% of dLys, which is historically considered the requirements in broilers. The authors concluded that mitochondrial arginase located in the kidney can hydrolyze arginine into ornithine (Furakawa et al., 2021) and then ornithine into proline by the enzyme ornithine-aminotransferase. This benefit in skin quality could have significant impact on broiler health and wellbeing during grow out, as well as economic importance due to improved performance, less disease challenge, and decreased condemnations during processing. Andeson et al., (2024;2025) reported in two separate studies that increasing dietary arginine led to linear increases in serum ornithine levels, thus supporting the conclusions put forth by Oliveira et al. (2022). FCR, g:g 2.150 2.10 2.050 2.0 1.950 1.90 1.850 1.80 1.750 1.70 69 79 89 99 109 119 129 139 dArg/dLys, % Figure 1. Digestible arginine to digestible Lysine ratio for optimization of feed conversion of YPM X Ross 708 male broilers from 25 to 42 day of age Adopted from Coro et al., (2021)
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