The experimentwas conducted with the objective evaluating the effect of supplementation ofglycine in diets with different digestible threonine:digestible lysine ratioson the activity of enzymes that metabolize threonine. Five hundred and sixtymale broiler chicks from the Cobb strain were used during the period of 8 to21 days, distributed in a completely randomized design, in a 3 × 2 + 1factorial arrangement, with 3 digestible threonine:digestible lysine ratios(55; 65 and 75%), with or without supplementation of glycine, plus an additionaltreatment, containing meat and bone meal, with a 65% digestible threonine:digestiblelysine ratio. Eight repetitions were used per treatment and 10 birds per experimentalunit, allotted in metal battery cages. The total excreta collection was performedthroughout the whole experimental stage. For the determination of the activityof the threonine aldolase, threonine dehydrogenase and threonine dehydrataseenzymes, at the end of the experiment, two birds were slaughtered and had theirlivers extracted. The threonine:lysine ratios influenced the activity of thethree enzymes in the liver; while the greatest activity of the threonine aldolasewas for the ratio of 75%, for threonine dehydrogenase it was 65%, and for thethreonine dehydratase it was 55%. Supplementation of glycine reduced the activityof all enzymes evaluated.
