SPECIAL STORY 58 FEED & ADDITIVE MAGAZINE September 2023 Kidd (2021) reported that the optimum valine ratio to optimize feed conversion ratio was increased from 74% dVal to 79% dVal when increasing the dietary leucine concentration (Figure 6). Corn based diets will typically have dLeu levels between 140 and 160% depending on available by-product meals. IMPLICATIONS AND CONCLUSIONS Prior to adoption of L-threonine use, multiple reports were unable to demonstrate the BCAA antagonism in industry type diets, most likely due to all BCAA being above the actual bird’s requirement allowing for a “proper” balance. However, as the industry continues to adopt the use of additional feed grade amino acids such as L-valine, L-isoleucine, and L-arginine and we continue to understand the benefits of reducing dietary crude protein, valine and isoleucine ratios are at or near the requirement which increases the potential of the presence of an antagonism when leucine is in excess. The presence of an antagonism, specifically with valine, can not only result in reduced animal performance but also impact feather condition and bone density (Farran and Thomas 1992a; Farran and Thomas 1992b). As we evaluate diets that may fall into this category, broiler and turkey corn-based finisher and withdrawal diets will always have higher leucine ratios as compared to starter and grower diets. Similarly, depending on the ingredient profile, broiler breeder, replacement pullet, and laying hen diets will undoubtedly have excess leucine with some US based diet approaching a dLeu: dLys ratio of 200. Thus, as an industry, we must begin to consider adjusting valine and/or isoleucine ratios used in industry diets based on dLeu, however, additional data is necessary to more accurately identify these ratio adjustments. Regardless, the most recent research demonstrating the BCAA antagonism clearly confirms the needs for BCAA prediction model in poultry similar to the Cemin et al. (2019) model in swine. The only question is must we develop a model based on species or strain? References 1. Cemin, H.S., M.D. Tokach, S.S. Drits, J.C. Woodworth, J.M. DeRouchey and R.D. Goodband. 2019. Meta-regression analysis to predict the influence of branch-chain and large neutral amino acids on growth performance of pigs. J. Anim. Sci. 97:2505-2514. doi:10.1093/jas/skz118. 2. Farran, M. and O. Thomas. 1992a. Valine deficiency. 1. The effect of feeding a valine-deficient diet during the starter period on performance and feather structure of male broiler chicks. Poultry Science. 71:1879-1884. 3. Farran, M. and O. Thomas. 1992b. Valine deficiency. 2. The effect of feeding a valine-deficient diet during the starter period on performance and leg abnormality of male broiler chicks. Poultry Science. 71:1885-1890., 4. Harris, R. A., M. Joshi, N. H. Jeoung, and M. Obayashi. 2005. Overview of the molecular and biochemical basis of branched-chain amino acid catabolism. J. Nutr. 135:1527S-1530S. 5. Jackson, S., and L. Potter. 1984. Influence of basic and branched chain amino acid interactions on the lysine and valine requirements of young turkeys. Poultry Science 63:2391-2398. 6. Kidd, M. 2021. Understanding the branched chain amino acid conundrum and how to use it to maximize performance. Poultry Science Association Annual Meeting, July 19-22, 2021. 7. Maynard, C., S. Liu, J. T. Lee. J. Caldas, J. Diehl, S. Rochell, and M. Kidd. 2021. Evaluation of branched chain amino acids in male Cobb MV x 500 broiler chickens by using Box-Behnken response surface design. Animal Feed Science and Technology (in press) doi:10.1016/j.anifeedsci.2020.114710. 8. Ospina-Rojas, I. C., A. E. Murakami, C. R. A. Duarte, G. R. Nascimento, E. R. M. Garcia, M. I. Sakamoto, and R. V. Nunes. 2017. Leucine and valine supplementation of low-protein diets for broiler chickens from 21 to 42 days of age. Poult. Sci. 96:914–922. Figure 6. Feed conversion ratio response curves of 28 to 42 d Cobb 500 broilers responses to increasing dietary valine content amid low (solid line -115%) or high (dashed line – 145%) dietary leucine (Adopted from Kidd, 2021).
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