Effects of different doses of Salix babylonica extract on growth performance and diet in vitro gas production in Pelibuey growing lambs

Twenty Pelibuey 3-4 month old and 23.7 +/- 3.3 kg body weight male lambs were used in a randomised design to study the effects of daily oral administration of Salix babylonica (SB) extract on dry matter (DM), water intake, average daily gain (ADG), and feed efficiency for 72 days. Animals were divided into four groups fed the same total mixed ration with different doses of SB: 0 (Control), 20 (SB20), 40 (SB40) and 60 (SB60) mL/lamb/d. In vitro gas production (GP) of the same diet fed to lambs as a substrate was measured with different doses of SB (0, 0.3, 0.7, 1.0 mL/g DM). Daily administration of SB to lambs had no effects (P=0.05) on growth performance and DMI (linear effect, P=0.2805; quadratic effect, P=0.3747). Both low and moderate doses of SB (SB40>SB20) tended to increase (linear effect, P=0.4010; quadratic effect, P=0.9166) ADG. The asymptotic GP quadratically increased (P<0.001) with decreased GP rate and with increasing SB extract doses. In vitro GP increased (P<0.05) with advancing of incubation time in all SB doses. During the first 24 h of incubation, 0.3 mL SB/g DM had the highest GP, whereas 1.0 mL SB/g DM quadratically increased (P<0.001) GP. The low dose of SB extract increased ME (linear effect, P=0.024) and short chain fatty acids (SCFA) (linear effect, P=0.023). However, the highest dose quadratically decreased (P=0.02) DM degradability. In conclusion, administration of SB extract at 40 mL/lamb/d tended to increase DM intake, improve daily weight gain in growing lambs with increasing asymptotic in vitro ruminal GP and SB dose.