Effects of energy level and Leucaena leucocephala leaf meal as a protein source on rumen fermentation efficiency and digestibility in swamp buffalo

Abstract

Four Thai – rumen fistulated male swamp buffaloes (Bubalus bubalis), about 3 years old with 360±18kg liveweight, were randomly assigned according to a 2×2 factorial arrangement in a 4×4 Latin square design to receive four dietary treatments. The treatments were as follows: a cassava based supplement (CS) at 1g/kg BW and Leucaena leucocephala leaf meal (LLM) at 300g/d (T1); CS at 2g/kg BW with LLM at 300g/d (T2); CS at 1g/kg BW and heat treated LLM (HLLM) at 300g/d (T3); and CS at 2g/kg BW and HLLM at 300g/d. During the experiment, urea–calcium hydroxide treated rice straw was given on ad libitum basis. The results revealed an increase in roughage and total dry matter (DM) intake (P<0.05) by CS at 2g/kg BW (T2 and T4) as compared with CS at 1g/kg BW (T1 and T3). Digestion coefficients of DM, organic matter (OM), and crude protein (CP) were increased by CS at 2g/kg BW, while neutral detergent fiber (aNDF) and acid detergent fiber (ADF) were similar among treatments. However, there was no effect of neither energy level nor HLLM on ruminal pH and temperature (P>0.05). Concentration of ruminal ammonia nitrogen (NH3-N) was decreased by HLLM as compared with LLM (P<0.05), while blood urea–nitrogen was not altered. There was an increase (P<0.05) in total volatile fatty acid (TVFA), acetic acid (C2), propionic acid (C3), and butyric acid (C4) concentrations and the highest were found in CS at 2g/kg BW with HLLM (T4), while the lowest was in T1 and T3. However, no changes in C2–C3 ratio were found in this study. Total bacterial direct counts were found different (P<0.05), whereas fungal zoospores and protozoal populations were similar among treatments. Nevertheless, viable bacterial counts were found affected by both concentrate level and HLLM. The treatments with HLLM were lower than those in LLM and CS at 2g/kg BW were higher than those supplemented at CS at 1g/kg BW (P<0.05). In addition, efficiency of rumen microbial CP synthesis tended to be higher in treatment with higher level of energy and HLLM. Based on this study, it could be concluded that LLM could be used as a protein source, while the combination of HLLM and CS at 2g/kg BW could enhance the voluntary feed intake, nutrient digestibility and rumen fermentation in swamp buffalo fed on treated rice straw (urea–calcium hydroxide treatment).