Influence of Salix babylonica and Leucaena leucocephala leaf extracts on ruminal fermentation characteristics, urinary purine derivative excretion and microbial protein synthesis of lambs

Sixteen growing Katahdin×Pelibuey lambs (24±0.3 kg body weight) were used to study the effects of oral administration of extracts of Salix babylonica (SB) and Leucaena leucocephala (LL) leaves on ruminal pH, total and individual volatile fatty acids (VFA) and NH3-N concentrations, as well as ruminal protozoal counts, urinary purine derivatives (PD) excretion and estimated microbial protein synthesis. Lambs were fed a total mixed ration (TMR) containing 219 and 141 g kg−1 of CP and NDF, respectively. Four treatments (4 lambs/treatment) were Control (no extract added), SB (SB extract at 30 ml d−1), LL (LL extract at 30 ml d−1) and SBLL (mixture of SB at 15 ml d−1+LL at 15 ml d−1). Extracts were administered orally to each lamb before the morning meal daily. Measurements were on days 22 (P1), 43 (P2) and 63 (P3) of the experiment. Ruminal pH increased (P=0.014) with SBLL extract and decreased with SB. The ratio of acetate to propionate was higher (P=0.042) with SBLL compared to the control. Ruminal NH3-N concentration was not affected by extract administration (P=0.309) or experimental period (P=0.087). Protozoal counts were not affected (P=0.489) by extract addition but decreased (P<0.001) in P3 compared with P1 and P2. Uric acid concentration increased (P<0.001) with individual extracts of SB and LL compared with the control or SBLL. Excretion of other purine derivatives (allantoin, xanthine, and hypoxanthine), creatinine and microbial protein synthesis were not changed (P>0.05) by extracts administration. Overall, oral administration of S. babylonica and L. leucocephala extracts, or their 1:1 mixture, to lambs for 63 d had only minor effects on ruminal fermentation, urinary purine derivative excretion and microbial protein synthesis.