Effect of supplementing urea treated rice straw and molasses with different forage species on the performance of lambs

Weaned lambs of the Phan Rang breed with an initial weight of 14.9 kg and 3.5 months of age were used to study the effect of supplementing urea treated rice straw (UTRS) and molasses with different forage species as protein sources compared to a commercial concentrate with respect to digestibility, growth performance and number of gastro-intestinal parasite eggs. Eight males were used in a digestibility trial in a double 4 × 4 Latin square design and 32 lambs (12 males and 20 females) in a growth trial lasting 84 days. The treatments were four diets containing urea treated rice straw ad lib and molasses supplemented with concentrate (control), Stylosanthes (Stylosanthes guianensis) forage (UTR-S), Cassava (Manihot esculenta Crantz) foliage (UTR-C) or Jackfruit (Artocarpus heterophyllus) foliage (UTR-J). The live weight gain (LWG) was 73.3, 70.0, 77.7 and 70.2 g/day and the feed conversion ratio 9.3, 9.0, 7.5, 10.4 kg DM/kg LWG for control, UTR-S, UTR-C and UTR-J, respectively. The DM intake ranged from 33 to 44 g DM/kg body weight. The DM digestibility was 0.66, 0.55, 0.60 and 0.54 and the CP digestibility 0.64, 0.65, 0.67 and 0.52 for the control, UTR-S, UTR-C and UTR-J, respectively. The nitrogen retained was 10.4, 9.8, 10.9 and 9.8 g/day for the diets control, UTR-S, UTR-C and UTR-J, respectively, and was not significantly different among treatments. The UTR-C and UTR-J diets had a weak effect on the number of Nematode eggs, which was reduced or slightly increased during the experimental period. In conclusion Stylosanthes forage and Cassava and Jackfruit foliage could be used as protein sources in diets based on urea treated rice straw and replace a commercial concentrate without any effect on the live weight gain of the lambs.