Optimal in-feed threonine and tryptophan ratio for replacement chickens: the theoretical background

M.J. Krivenok, I.I. Ilchuk, V.M. Mykhalska


We determined the optimal content and ratio of threonine and tryptophan in the mix fodder of replacement chicks at different periods of their growing. We studied the effect of different levels of threonine and tryptophan in mixed fodder on chicken growth and development. We registered that under optimal AA content and ratio the replacement chickens at the end of the growing period outweighed the chickens from control group by 140 g. We also studied the influence of different content of AA and temporal changes in their ratio on digestibility of feed nutrients by replacement chickens from market egg flock. It was found that the optimal content of threonine and tryptophan and their ratio at certain periods of chicken growth caused the increase in digestibility of protein by 2 %, fiber – by 1 %, and BEV – by 2 %. We also proved that the decrease or increase of AA ratio in mix fodder of replacement chickens leads to the manifestation of antagonism between amino acids and the deterioration of their function in bird organism. The changes in AA ratio had significant effects on chicken productivity, the digestibility of feed nutrients, the assimilation, and efficiency of amino acid use. This effects were considerably stronger than the effect of changes in AA content. The degree of influence of the ratio between threonine and tryptophan varies throughout the growing period, it has been established that the ratio of threonine to tryptophan in the period of limited chick feeding (9-6 weeks) has a lesser effect on the productivity of repair young (R2 = 0.89) the second one (R2 = 0.92) and the last growing periods (R2 = 0.92). We performed a mathematical model (polynomial trend line) to describe the growth of replacement chickens during all experiment periods, the pattern of dependences between chicken organism and AA content, AA ratio, age, and productivity. This nonlinear model is more relevant and reliable than linear dependence.


replacement chickens; essential amino acids; threonine; tryptophan; optimal dietary AA ration

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DOI: http://dx.doi.org/10.15421/2017_57

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© 2017 Ukrainian Journal of Ecology. ISSN 2520-2138