K. R. Pond

Intake, digestibility and nitrogen utilization of three tropical tree legumes: I. As sole feeds compared to Asystasia intrusa and Brachiaria brizantha

The tropical tree legumes Paraserianthes falcataria, Gliricidia sepium, and Calliandra calothyrsus were fed to ram lambs to evaluate their potential as feeds. Dry matter intake, digestibility of dry matter, neutral detergent fiber and nitrogen, and digestible energy content were determined through a digestion study. The herbaceous dicot Asystasia intrusa was included as an underutilized source of nitrogen and Brachiaria brizantha was included as a standard tropical (C4) grass. Of the tree legumes, C. calothyrsus had the highest level of soluble phenolics (SPHE), averaging 38% of dry matter, and soluble proanthocyanidins (SPRO), averaging 13.7 absorbance units per gram (AU g ˇ1 ) of dry matter. P. falcataria was intermediate, averaging 15% SPHE and 4.8 AU g ˇ1 SPRO, with G. sepium the lowest, with 5% SPHE and 0.4 AU g ˇ1 SPRO. Dry matter intake (percent of body weight) was lowest for C. calothyrsus-fed lambs, averaging 2.0%, compared with 3.2% for P. falcataria and 2.5% for G. sepium. Intakes were similar for A. intrusa and B. brizantha, averaging 2.6%. C. calothyrsus also had the lowest dry matter digestibility, averaging 55%, compared with 61% for P. falcataria and 63% for G. sepium, which were similar. Highest dry matter digestibility was obtained for A. intrusa, averaging 72%, and B. brizantha, averaging 65%. Forages had similar rank for neutral detergent fiber digestibility.

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

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