Intake, digestibility and nitrogen utilization of three tropical tree legumes

Calliandra calothyrsus, Paraserianthes falcataria and Gliricidia sepium leaves were supplemented at both 25 and 50% of dietary crude protein to a basal concentrate and fed to growing ram lambs. A control diet consisted of concentrate and the forage grass Brachiaria brizantha. Dry matter intakes and ADG of tree legume supplemented treatments were lower (P < 0.05) than control lambs, but increasing the amount of tree leaves fed did not result in further decreases in either dry matter intake or ADG. Dry matter digestibility was lower (P < 0.05) in both 25 and 50% dietary treatments compared with the control, while NDF digestibility was lower (P < 0.001) only in the 50% dietary treatments. Increasing the amount of leaves fed from all three tree species, led to decreased NDF digestibility. Fecal NDF-N was higher in tree-supplemented groups (P < 0.01) compared with control and increased (P < 0.05) with increasing amounts of tree leaves fed. Both apparent and true N digestibility were lower (P < 0.05) in C. calothyrsus, than in the other tree legume treatments. True N digestibility of 91% for the control was higher (P < 0.01) than the tree legume treatments supplemented at both 25 (range, 83‐86%) and 50% dietary CP (range, 74‐79%). Increasing the amount of tree leaves fed, regardless of tree species, decreased N digestibility in the diets. Higher fecal NDF-N and lower N digestibility in tree leaf supplemented lambs indicated that condensed tannins present in these tree species were binding protein and rendering it less available for digestion. Supplementation with C. calothyrsus, which had the highest levels of SPHE and