The ability of tanniniferous legumes to reduce methane production and enhance feed utilization in Barki rams: in vitro and in vivo evaluation

Two experiments (in vitro and in vivo evaluation) were conducted to evaluate the ability of three different tanniniferous legumes to replace berseem hay on ruminal fermentation, digestibility and methane (CH₄) emission. Berseem (Trifolium alexandrinum L.) hay (BH) was considered as control, or replaced at 50 % with Acacia saligna (AS), Leucaena leucocephala (LL) or Atriplex halimus (AH) on a DM basis. In Experiment 1 (in vitro evaluation), in vitro ruminal degradability, gas and CH₄ production were measured. In Experiment 2 (in vivo evaluation), twelve Barki rams weighing 43.29 ± 0.13 kg were randomly assigned into 4 treatments and individually fed the BH, AS and LL diets for 30 days (21 days for adaptation, 7 days for digestibility and N balance and the subsequent 2 days for CH₄ measurements). Results of Experiment 1 showed that AS, LL and AH diets decreased (P < 0.05) gas, CH₄ and total protozoa compared to BH. Both AS and LL diets increased (P < 0.05) ruminal propionate and partitioning factor, while decreased, ammonia-N (NH₃-N) concentrations, acetate, acetate/propionate ratio and protozoa count compared to the BH diet. In Experiment 2, the LL diet decreased (P < 0.05) dry matter intake and digestibility of crude protein compared with the BH diet. Rams fed both AS and LL diets showed greater (P < 0.05) fecal N and retained N, while decreased (P < 0.01) urinary N excretion and exhibited 11.45 % reductions in CH₄ production. In conclusion, the partial replacement of BH with AS reduced N losses and CH₄ emissions without negative effects on ruminal fermentation.