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

Khuc Thi Hue, Do Thi Thanh Van ^* and Inger Ledin ^**

 Goat and Rabbit Research Center Sontay, Hatay, Vietnam
*National Institution of Animal Husbandry, Hanoi, Vietnam
* Department of Animal Nutrition and Management,
Swedish University of Agricultural Sciences PO Box 7024, 750 07 Uppsala, Sweden

Forty weaned Phan Rang lambs 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 and molasses with different forage species, Stylosanthes (Stylosanthes guianensis), Cassava (Manihot esculenta Crantz) or Jackfruit (Artocarpus heterophyllus), 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 thirty two lambs (12 males and 20 females) in a growth trial lasting 84 days.

The crude protein (CP) content in the concentrate, Stylosanthes forage, Cassava foliage and Jackfruit foliage was 171, 154, 202 and 148 g/kg dry matter (DM), respectively. The treatments were four diets containing urea treated rice straw ad lib and molasses supplemented with concentrate (control), Stylosanthes forage (UTR-S), Cassava foliage (UTR-C) or Jackfruit 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, 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.

Key words: Urea treated rice straw, molasses, Stylosanthes guianensis, Manihot esculenta Crantz, Artocarpus heterophyllus, lambs, growth, digestibility and parasites.