Determination of the optimal digestible arginine to lysine ratio in Ross 708 male broilers
Published:September 6, 2021
Summary
DESCRIPTION OF PROBLEM Broilers have specific essential amino acid requirements that must be met in order to support growth, muscle development, and meat yield (Mack et al., 1999; Zampiga et al., 2018). Continued genetic selection of broiler strains focused on increasing feed intake and meat yield and improving growth efficiency will require adjustments in formulation, particularly in amino ac...
As a Nutritionist and having formulated a lot of diets over the years, I appreciate the desire to have a point estimate of the dArg/dLys ratio. I also appreciate your contribution toward that goal.
Given the low to extremely low R square values for your regression models, it would seem to me that the "optimal" ratios from your conclusions cannot be very precise. How would you advise formulators to use the point estimates you have provided? Is there some standard that should be applied to goodness-of-fit of a model used to make nutrient recommendations?
I congratulate the team of researchers involved in the idealization and implementation of this study, with emphasis on the methodology, especially in the number of birds per experimental unit and in the number of replicates. It is also worth highlighting the fact that the authors used suboptimal levels of lysine in the experimental diets, which makes total sense. Despite the positive aspects highlighted, I think that two treatments were missing. The first would correspond to a basal ration with all the nutrients, including lysine and arginine, meeting the requirement of the birds. And the second would correspond to a ration similar to the previous one with the suboptimal level of lysine, as established. These treatments would serve to prove that the suboptimal level of lysine compromised the performance of the birds
Congratulations for this splendid work. The number of birds analyzed for carcass is really impressive.
I just can't see from the numbers how you could get to a maximum response for carcass yield of 136 when the maximum value was attained at 109%. It looks like a broken-line (with a linear ascending term) would have been a better option and fit the data as well as the quadratic model.
Dr. Corzo, thanks for the effort to further investigate the digestible arginine/digestible lysine ratio in broilers. However, I have a few questions:
1- How do you reconcile your Conclusions and Applications in the paper of Mejía et al. (2012) of which you are also a co-author and those in your paper of 2021? In 2012 working also with Ross 708 you concluded that a minimum ratio of 110% was adequate and further, the paper also concluded that “higher dArg:DLys ratios fed during summer-type conditions to broilers rear in broiler houses in a control environment have little effect on growth or the CARCASS CHARACTERISTICS of the broilers” (the emphasis is mine). Your 2021 paper cites Mejía et al., but you don’t discuss why the differences in the findings. Is it that Ross 708 has changed so much?
2- I understand that in order to have some specific ratios in the basal diets sometimes you have to use formulation that have nothing to do with the commercial reality. For instance, the formula for the Finisher (25-42d, period in which normally most of feed intake occurs under commercial conditions) contained only 3.57% soybean meal. Do you think that your conclusions on the dArg:dLys ratio apply to the industry, particularly those related to carcass characteristics? It is interesting, in my view, that the experimental diets in the Mejía et al. (2012) paper aligned more closely to what the poultry industry uses, at least in the United States.
3- Finally, while the plots in Figures 1, 2, and 3 have no stated equations nor R-square values?
In fact, the dArg: DLys has a lot of debt since the work co-authored by JT Brake from NCU and my work published 2006 &2011 there is no clear effects showing the need for further works to identify the factors influencing the response to Arg:Lys ratio.
Attia, Y. A., Barbara M. Böhmer, Dora A. Roth-Maier (2006). Responses of broiler chicks raised under constant relatively high ambient temperature to enzymes, amino acid supplementations, or a high-nutrient diet. Archiv Für Geflügelkunde 70 (2): 80-91. Attia, Y. A., R. A. Hassan, A. E. Tag El-Din, and B. M. Abou- Shehema (2011). Effect of ascorbic acid or increasing metabolizable energy level with or without supplementation of some essential amino acids on productive and physiological traits of slow-growing chicks exposed to chronic heat stress. J. of Animal Physiology and Animal Nutrition 95:744-755.
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