Intake, digestibility and nitrogen utilization of three tropical tree legumes II. As protein supplements

Calliandra calothyrsus, Paraserianthes falcataria and Gliricidia sepium lea ves were supplemented at both 25 and 50% of dietary crude protein to a basa l concentrate and fed to growing ram lambs. ii control diet consisted of co ncentrate and the forage grass Brachiaria brizantha. Dry matter intakes and ADG of tree legume supplemented treatments were lower (P < 0.05) than cont rol lambs, but increasing the amount of tree leaves fed did not result in f urther decreases in either dry matter intake or ADG. Dry matter digestibili ty 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 tre e species, led to decreased NDF digestibility. Fecal NDF-N was higher in tr ee-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 tr ee legume treatments. True N digestibility of 91% for the control was highe r (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 d iets. Higher fecal NDF-N and lower N digestibility in tree leaf supplemente d lambs indicated that condensed tannins present in these tree species were binding protein and rendering it less available for digestion. Supplementa tion with C. calothyrsus, which had the highest levels of SPHE and SPRO, af fected N utilization more negatively than did supplementation with either P . falcataria or G. sepium. (C) 1999 Elsevier Science B.V. All rights reserv ed.