A study was carried out to evaluate some protein-rich forages (Stylosanthes guianensis, Manihot esculenta Crantz, Artocarpus heterophyllus) as replacement for a commercial concentrate in a basal diet of urea treated rice straw to improve the performance of growing lambs and to reduce the price of the animal products. The study was realised at the farm of the Goat and Rabbit Research Center, Bavi, Vietnam, from March to September 2006.
In the growth experiment 32 lambs, 12 males and 20 females, with a mean weight of 14.9 kg and 3.5 months old were used to study feed intake, live weight gain (LWG) and feed conversion ratio (FCR). The lambs were randomly assigned to four treatments in a completely randomised design but with consideration to sex. The treatments were a basal diet of urea treated rice straw + molasses supplemented with a commercial concentrate (control), Stylosanthes forage (UTR-S), Cassava foliage (UTR-C) or Jackfruit foliage (UTR-J). The experiment was run for 84 days. There was a significant difference in dry matter intake (DMI) among treatments, but no significant difference in intake expressed as g DM/kg BW (38 g, 34 g, 33 g and 44 g/kg BW) or LWG (73.3 g, 70.0 g, 77.7 g and 70.2 g/day) for the control, UTR-S, UTR-C and UTR-J treatments, respectively. The FCR were 9.3 kg, 9.0 kg, 7.5 kg and 10.4 kg DM/kg LWG and the cost/kg LWG of the experimental diets was 90.5%, 56.2% and 35.7% of the cost of the control for UTR-S, UTR-C and UTR-J, respectively.
The evaluation of the effect of tannins in the experimental foliages on number of parasite eggs in the faeces showed that the tannins in the Cassava and Jackfruit in UTR-C and UTR-J had a variable effect on the number of Nematode eggs which was reduced or slightly increased during the experimental period, but had no clear effect on the number of Cestodes and Coccidia oocyst eggs.
A digestibility experiment using lambs of the same weight and the same diets as in the growth experiment in a double 4*4 Latin square design showed that the DM digestibility was significantly higher for control and UTR-C and lower for UTR-S and UTR-J. The CP digestibility was higher and similar for the control, UTR-S and UTR-C. The nitrogen retained was 10.4 g, 9.8 g, 10.9 g and 9.8 g/day for the control, UTR-S, UTR-C and UTR-J, respectively, but even though there was a difference in DM and CP digestibility among the diets this did not result in any differences in N retention.