Abstract
A study was conducted to evaluate the replacement value of Leucaena leucocephala and Gliricidia sepium as nitrogen sources in commercial type supplements for dairy goats. Six crossbred $(Toggenburg{\times}Saanen)$ goats at late stage of lactation were allocated to three dietary treatments in a double $3{\times}3$ Latin square design. The animals were offered rhodes grass (Chloris gayana) hay ad libitum and supplemented with either Leucaena-based concentrate (LBC), Gliricidia-based concentrate (GBC) or commercial based concentrate (CC). Voluntary food intake, milk yield and composition and changes in live weight were measured. The total dry matter (DM) intake was higher (p<0.05) in goats fed GBC than CC (1385 vs 1331 g/d). The DM intake for LBC (1343 g/d) was similar to CC (1331 g/d). The DM intake of hay was also higher (p<0.05) in goats fed GBC (834 g/d) than those receiving LBC or CC (789, 782 g/d, respectively). Animals supplemented with GBC recorded positive (11 g/d) weight gain while the other groups lost weight (13, 19 g/d) for LBC and CC respectively, although these differences were not statistically significant (p>0.05). The composition of milk were: butterfat 58, 49 and 55 g/kg; crude protein 37.0, 35.4 and 36.1 g/kg; lactose 33, 29 and 30 g/kg; Ash 8.5, 8.5 and 7.9 g/kg and total solids 136.5, 121.9 and 129.0 g/kg, for goats fed LBC, GBC and CC respectively. There were no differences in the composition of milk due to these dietary treatments. At the end of performance trial, a digestibility trial was conducted using 6 female goats allocated to the three treatments (LBC, GBC and CC) in an incomplete randomized block design and each goat received a different supplement in each of two successive periods. There were no differences in nutrient digestibility except for DM, which was higher (p<0.05) in CC compared to the other treatments (615, 622, 720 g/kg for LBC, GBC and CC, respectively). Economic analysis showed that CC diet was more expensive (0.20 US$/kg) and had a lower margin over supplementation (0.11 US$) compared to LBC and GBC (0.13 vs 0.12 US$/kg and 01.5 vs 0.12 US$, respectively). It is concluded that the Leucaena and Gliricidia could contribute as nitrogen sources in compounded diet supplements without any detrimental effects on production in dairy goats.