Utilisation of Leucaena diversifolia, Leucaena esculenta, Leucaena pallida and Calliandra calothyrsus as nitrogen supplements for growing goats fed maize stover

Three psyllid resistant Leucaena species (Leucaena esculenta sub-species paniculata (Oxford Forestry Institute, accession number 52/87), L. diversifolia sub-species stenorcarpa (Oxford Forestry Institute, accession number 53/88) and L. pallida offspring of Commonwealth Plant Introduction, number 85890)) and Calliandra calothyrsus (Oxford Forestry Institute, accession number 9/89) were evaluated for their potential as supplements for growing goats fed maize (Zea mays) stover, using chemical analyses, in vivo digestibility and a growth trial. Leucaena esculenta forage had the highest (P<0.001) content of nitrogen (38.3 g kg−1 DM) compared to L. diversifolia, L. pallida and C. calothyrsus, with 36.3, 34.8 and 34.0 g kg−1 DM, respectively. Levels of insoluble proanthocyanidins and soluble phenolics were highest (P<0.001) in C. calothyrsus forage, moderate in L. esculenta and L. diversifolia and lowest (P<0.001) in L. Pallida. Soluble proanthocyanidin concentrations differed significantly (P<0.001) between fodder tree legumes and ranked in the order L. esculenta and L. diversifolia > C. calothyrsus > L. pallida. Mean apparent digestibility coefficient of nitrogen for the diets supplemented with C. calothyrsus, L. diversifolia and L. pallida was 0.56 and differed significantly (P<0.001) from that reported for goats on L. esculenta (0.46). Highest (P>0.05) nitrogen retention was reported for goats on the L. diversifolia supplement (0.45 g kg−1 W0.75 per day) and the mean nitrogen retention for goats on C. calothyrsus, L. esculenta and L. pallida was 0.43 g kg−1 W0.75 per day. In the growth trial, total dry matter intake was highest (P<0.05) with goats on the L. pallida and C. calothyrsus supplemented diets. Growth rate during the last 35 days of the study was highest (P<0.001) for goats on the C. calothyrsus supplement (44.2 g per day) reflecting a high nitrogen use efficiency, while those fed the L. esculenta, L. diversifolia and L. pallida gained 27.5, 37.8 and 40.6 g per day, respectively. The different impact of tree fodder proanthocyanidins on animal responses emphasises the need to identify and define their chemical and functional structures in order to understand the biological effects of different proanthocyanidins on ruminant performance.